How and with what should you polish wooden surfaces? Techniques for working on a wood lathe Stages of polishing work
K category: Miscellaneous
Final finishing of wooden products
By finishing wood products we mean sanding, painting, varnishing and polishing them.
Sanding of wooden products is done with sandpaper, horsetail and pumice. Real skin is the skin of a fish from the stingray breed - a sea dog, which is characterized by strong roughness, but usually when processing wood, artificial skin is used - paper, smeared with liquid glue and sprinkled with finely ground glass. There are several numbers of such skins on sale, differing in the more or less coarse grain of the glass on it. Horsetail is a tough marsh grass that, when dried and tied into bunches, is also used to clean the last imperfections on wooden surfaces. Pumice is burnt volcanic lava and is sold in chunks or powder. If you plan to sand the wood with piece pumice, then you need to cut the existing piece of pumice into two parts and rub the cuts thoroughly against each other, having previously lubricated them with oil or lard; this friction should completely smooth out the surface of the piece of pumice; this is necessary so that no scratches are left on the wood when sanding.
When sanding, pumice is moistened with oil, and if you do not want the color of the wood to change, with lard, and, pressing lightly, rubbed over the surface to be sanded.
As with the previously described work on finishing wooden products, sanding is also carried out in a certain sequence - first with coarse-grained sandpaper, then with finer sandpaper and, finally, with pumice. If the latter is available in powder, then it is collected in a small amount on a cloth, also moistened with oil or lard, and rubbed in the same way as with a piece of pumice.
In order for the surface of the wood to better accept paint, varnish or polish, you can also etch it, either by smearing it with a ready-made mordant, or by making it yourself.
Most common brown mordant can be made by boiling 1 part aloe in 6 parts hydrochloric acid. During boiling, red vapors are released from the liquid, which then disappear. After this, the mordant is diluted with 20 parts of soft water (rain), and it is ready for use. Boiling, due to the release of vapors, is best done in the open air.
If the wood is painted a dark color, then you can lubricate the wood with this stain several times, if it is a light color - once.
After etching, it is good to sand the entire surface again with pumice (before etching, you can limit yourself to only sanding with sandpaper).
When grinding is completed, you should not forget to remove from the surface being treated any remaining oil that was used to wet the pumice. This is done using a soft cloth or passing paper, and then sprinkling the surface to be treated with fine bran powder or chalk. The bran absorbs the last remaining oil. After a few hours, the bran can be swept away and the sanded surface can be finally wiped with a soft cloth.
Polishing. Immediately after grinding, the product is polished.
Polishing protects the wood from external influences that destroy it and gives the product a beautiful appearance, making its surface mirror-shiny, with all the veins and stains of the wood visible through this shine.
The polish needed for polishing can be purchased at the store.
When polishing, take a piece of woolen cloth and roll it into a ball, but so that the lower part is completely flat. Having moistened this flat side with polish, wrap the wool ball with a rag of old worn-out linen and, taking the ends of the rag into your hand (in a knot), pour a few drops of raw linseed oil onto the side of the resulting tampon, which will be used to rub on the wood. The swab is moved over the surface to be polished, pressing lightly and evenly until the entire surface is covered with an even layer of polish. When the polish is used up, unroll the cloth, moisten the ball of wool with the polish, wrap it again in the cloth and, having moistened the latter with oil, as already described, continue polishing.
If during work the cloth begins to stick to the surface being polished, this means that the polish has become too thick and must be diluted with alcohol. When the polish covers the entire surface so that it becomes smooth, the linen cloth is replaced with a clean cloth moistened with alcohol, and the entire surface is wiped with it again until it becomes completely shiny. In this case, you should not take too much alcohol, but only a few drops; otherwise you can wash off the polish itself.
The surface coated with polish should be thoroughly dried and the polish should be allowed to saturate all the pores of the wood. It’s good, a few days after the first polishing, polish the item a second time. This will make its surface even harder, smoother and more shiny.
Simultaneously with polishing, you can also tint the workpiece; then some paint powder should be added to the polish. This is done like this: a ball of wool soaked in polish is wrapped not in one, but in two linen rags, between which a thin layer of paint is applied. Polishing is carried out in exactly the same way as in the first case, but only the polish, seeping through the canvas, carries with it part of the coloring matter, which is rubbed with it evenly over the surface being treated.
In this way, cheap types of wood are imitated to look like expensive ones, for example, red or others. Of course, in every special case It is necessary to carefully select the color of the dye used.
Varnishing. While polishing is used mainly for finishing fine objects, varnishing is more widely used. Its essence consists in covering the product with varnish using brushes.
Varnishing should be done with even, quick strokes, and you should pay attention to the fact that the varnish is applied in as thin and even a layer as possible, otherwise the surface will take on an unsightly appearance and the varnish will take a very long time to dry.
When varnishing, the surface takes on a fairly beautiful appearance in one go, relatively rarely. Typically, you should let the varnish dry and coat the entire surface with varnish a second time. If this time too appearance will not be beautiful enough, then after the varnish has dried, you should wipe everything with fine sandpaper (without making scratches) and varnish it again.
As general guidance When should polishing be preferred, and when varnishing, let’s say that only large surfaces that allow freedom of circular movements with a swab with varnish can be polished; the same things as thin or narrow parts of furniture, legs of tables and chairs, RUSHES and armrests of chairs should be varnished, since it is more convenient to work with a brush.
Wax finish. A wooden product will also look beautiful if it is finished with wax. To do this, melt in clay pot 2 parts wax with 1 part turpentine. When melting the wax, you should stir it all the time. When the wax and turpentine are fused into a completely homogeneous mass, the entire mass is cooled and rubbed onto a wooden surface using a cloth or a stiff brush. Then the board is rubbed again with a dry cloth, and it acquires a beautiful matte shine.
Beautiful types of wood can be finished with wax directly; less valuable ones can be painted before waxing.
Polished, varnished and waxed items require careful handling - their surface deteriorates from dampness, and therefore they cannot be wet; You should also not place hot dishes on them, as this will leave indelible marks.
Turned products are polished, varnished and waxed lathe. To do this, make a cotton swab for varnish or a wool swab with a linen wrap for polish and collect liquid on them, just as in previous cases, slowly move these swabs along the product, which at this time is rotating in the machine.
To finish a turned object with wax, fuse 5 parts of wax with 2 parts of turpentine and first cover the thing with the mixture, which has not yet completely cooled, and then, rotating this thing in the machine, run a cloth over it until the desired shine is achieved.
Coloring. The finishing methods we described related mainly to such products that, due to the nature of their purpose, should be located indoors. As for those objects that should be exposed to the air, they should be painted with oil paint to protect them from dampness, rotting, insects and other influences.
Simple oil paints for coating carpentry are prepared using drying oil.
Before painting begins, the object is puttied and primed. Putty is the sealing of all the cracks and cracks of a wooden surface with chalk putty diluted with water and mixed with drying oil into a thick dough. The primer is made with very liquid oil paint, which should be well absorbed into the wood. Its color may not exactly correspond to what the item should have in its final form, but it is still better to use a light primer for a light color, and a dark one for a dark color.
The actual painting is done after the primer layer has dried. In order for the paint to be sufficiently durable, it is necessary to paint over the same place at least twice, and before painting the second time, it is necessary that the first layer has time to dry and be properly sanded. In this case, sanding should be done with fine sandpaper.
Painting is done with bristle brushes, which should not take too much paint at one time; The paint should be evenly rubbed into a thin layer, trying to spread as much as possible. larger area treated surface. The paint is used well mixed; and if it was prepared in advance, you should make sure that it is not covered with a crust. If this crust is present, then carefully remove it first, otherwise, pressed through with a brush, it will float in the paint in pieces and, getting on the brush, and from it onto the surface to be painted, will leave unsightly lumps and lumps on it. To protect the paint from being covered with such a crust, you should fill the paint cans with water after finishing the work; the same paints, which by their composition absorb water, should be filled with oil.
Bristle brushes used for painting large surfaces should be wide and have long hair. However, since long hair is inconvenient to work with, then such a brush should be tied with dense rows of rope so that only relatively short ends of the hair stick out, and then, when the hair wears off as you work, gradually remove the layers of rope, thus revealing the still untouched part of the bristles. .If necessary, paint fine lines using so-called line brushes made from horsehair.
It should immediately be noted that if necessary, renew an old item on which the color has deteriorated ( Oil paint deteriorates very much from the sun), you should not apply a new layer of paint directly on a dry old one. The only thing that will happen from this is that the old layer of paint will absorb the oil from the fresh layer, and this latter will soon peel off. You have to do this: add a little oil to the layer of old paint, and then it will take on its own. old look; If you want the paint to have a completely fresh appearance, then after soaking and drying the first layer of oil, you need to wipe the surface several times with oil containing a small amount of paint. This renewal will achieve its goal.
- Final finishing wooden products
Today, turned parts are widely used in the production of furniture, interior design, creating household utensils, souvenirs, toys and other items. Such products are both constructive and decorative in nature.
Wood turning more fully reveals the decorative qualities of this material and creates the opportunity to use common types of timber that do not have a beautiful texture. In addition, turning production actively uses shrub wood and waste, which is obtained during cutting lumber at wood processing plants.
Types of turning
Wood turning is carried out using several methods:
- longitudinal. During such processing, the workpiece rotates around its axis, and the cutter smoothly moves in a direction parallel to the rotation axis
- transverse. In this case, the cutter moves in a plane that is perpendicular to the axis of rotation of the workpiece
- angular (tangential). During such processing, the cutter moves at an arbitrary angle to the axis of rotation.
Machine selection
If you work with wood just for fun, and you don’t have a full-fledged workshop with a full set of all tools, then choosing a machine is very important stage. There are certain criteria that you should pay attention to when purchasing a machine:
- the maximum size of the workpiece placed in the machine. The turning diameter is always indicated in the accompanying documents for the machine - largest section workpieces in the transverse direction, as well as the length of the bed - maximum length blanks
- power. Of course, the best are machines with high power. However, an increase in power entails an increase in the dimensions of the machine.
- the material from which the bed and frame are made. The most stable machine will be with a steel frame and cast iron bed. But the mass of such a tool is quite impressive, so if you often move the machine, then take a closer look at lighter models. There are devices in which the frame and body are made of light alloys; they can be easily moved, even alone
- range of adjustment of the number of revolutions per minute. Fortunately, today all machines are equipped with this adjustment, so pay attention to the upper and lower limits of the range. For example, low speeds are necessary for rough processing of a parallelepiped, and high speeds are needed during finishing processing, when a perfectly smooth surface is required.
Types of machines
Wood turning technology involves the use of devices of various modifications:
- universal machines. They can be used to peel the workpiece, cut it, turn it, grind it, drill it, and apply thread. Due to their versatility, such machines are in high demand.
- screw lathes are designed for processing workpieces in the form of a cone, as well as applying threads
- turning and milling machines are designed for making grooves in wooden objects, as well as their processing
- A benchtop turning tool performs the functions of a conventional machine, but has smaller dimensions, power and fewer functions. Such machines are suitable for getting acquainted with the craft and gaining initial skills.
Main stages of work
Turning wood on a lathe must begin with creating a workpiece. To do this, you need to take a block of any type of wood. Please note that the size of the workpiece must be several times larger than the size of the intended product. Using an ax you need to give the workpiece approximate form cylinder. Even experienced craftsmen You should not attach a solid block to the machine, because you can get injured when large pieces of wood bounce off. After this, you need to designate the places where the shape will be turned, that is, marking the centers of rotation.
The technology of turning wood on a lathe involves the use of turning tools. In order to process the blank you will need three chisels:
- grooved to remove rough upper layer from the workpiece
- grooved semicircular concave in order to prepare the product for finishing
- An oblique chisel will help to grind a cone, trim the ends and carry out finishing.
Before starting work, you need to sharpen chisels and any cutting tools.
All machines have space for securing the workpiece. Most often this is a hexagon with spikes. To avoid the workpiece falling out of the mechanism during operation, it is recommended to make indentations at its ends where the spikes touch.
The turning process itself begins with the full launch of the shaft. Once the speed is up, you can begin finishing the wood.
At the beginning, rough processing is carried out. To do this, the rotation speed must be in the range of 1000-1500 rpm. You can use a semicircular chisel. You need to hold the tool with both hands, leaning on the tool rest. However, you should not put pressure on the workpiece.
After removing the top layer, you can take a grooved semicircular chisel. With its help, a contour of the recesses is created. The pointed end of the device should be directed towards the part at an angle of approximately 45. Thus, you implement the process artistic carving on wood.
A properly processed object does not need additional sanding; its surface will be perfectly smooth.
Wood lathe - 3
Enthusiasts build lathes to turn wood. I wasn’t too lazy and found a text that suited the occasion online. It’s not new, to put it mildly, but it’s better for me to add to it later or comment on it than to fence a garden on empty space. In addition, it is of a certain value as a monument to the era. What does a military-grade cast iron machine cost?in the picture in the text.
A.M. Konovalenko
Wood turning
Among mechanized types wood processing, turning is considered one of the most ancient. Wood turning, like wood carving, is one of the most common types of artistic wood processing. Simplicity of operation and the ability to quickly produce turned products, achieving a high degree of polishing, laconism and harmony of forms - all this contributes to wide application this type of wood processing. In addition, a variety of techniques allows you to grind details of any complexity. Possessing this skill, a resident of the city and village can create a unique interior at home, where turned products will perform both utilitarian and decorative functions.
When turning, cutting is carried out by rotational movement of the workpiece and longitudinal (axial), as well as radial and tangential movement cutting tool- submissions. At home, lathes are used, where the feed is carried out not mechanically, but manually, which requires certain knowledge and experience from the performer. Depending on the type of surface treatment, there are different cutting modes during turning: turning, boring, trimming (facing). There are also such as cutting ledges, turning grooves, cutting threads, etc.
Turning can be carried out both along (longitudinal turning) and across the wood fibers. The final stage in the manufacture of turned products is finishing. For textured species - oak, walnut, pine, cedar, mahogany - transparent ones are mainly used decorative coverings- varnish, polishes, beeswax, etc. And for low-value species with an inexpressive texture - alder, birch, aspen, linden, some varieties of beech - additional artistic finishing is used: carving, painting, etching to resemble more valuable species, firing, burning, finishing with mother-of-pearl, metal, etc.
Turned parts can be diversified by using rectangular elements. To do this, the corners of the turned shapes are cut. Sometimes the turned part is used for edging rectangular planes of furniture. They do it as follows. Grinded according to a template cylindrical part with many grooves, the edges of which are rounded. Then such a part is cut symmetrically into four parts, which are used to cover (in the form of a carved border) the edges of the plane.
Turned parts are most often used for furniture. Here they serve as decoration. The turned elements must be compositionally linked to the product and to the interior as a whole, both in style and scale.
Lathes and cutting tools
Let's consider the design of a desktop lathe (Fig. 1). The lathe bed (1) is made of metal (in homemade designs it is made of hard wood). All the main components of the lathe are mounted on it. The headstock of the lathe (4) is stationary and is bolted to the bed. It is made primarily from cast iron in the form of shaped castings. The headstock brackets contain bearings pressed into it, where the lathe spindle (5) rotates. In its central part there is a two-stage pulley, which through a belt drive (2) transmits rotation to the spindle from the electric motor of the lathe (7). The pulley, belt drive, and electric motor of the lathe are protected by a casing (3). The right end of the lathe spindle has a thread for installing lathe chucks (6), into which a wooden workpiece is mounted for turning. The purpose of the headstock is to secure the part and ensure its rotation. The tailstock (10) can reciprocate along the lathe bed. It consists of a cast iron body, in the upper part of which there is clamping mechanism, and at the bottom there is a fixing one that holds the tailstock in the required position.
Rice. 1. Tabletop wood lathe:
1 - bed; 2 - belt drive; 3 - casing; 4 - front headstock; 5 - spindle; 6 - lathe chuck;
7 - electric motor; 8 - tool rest; 9 - carriage; 10 - tailstock; 11 - steering wheel;
12 - carriage fastening handle; 13 - wood slab; 14 - table; 15 - push button switch
The clamping mechanism is a spindle with a cone at one end. The other end is connected to the steering wheel (11). When the handwheel rotates, the lathe spindle presses the part in the centers. The spindle axes of the headstock and tailstock lie on the same straight line.
Lathe tool rest (8) with carriage (9). The first serves as a support for moving the cutting tool along it during operation. The carriage has a hole for attaching a tool rest with a roller. The handle (12) fixes the feather-comb of the tool rest at the required height and at a certain angle. Using the carriage, the tool rest can be installed at an angle, which makes it possible to turn parts to a cone. On the left side of the lathe bed there is a push-button switch (15) for the electric motor. The lathe is bolted to a block of wood (13) mounted on two pieces of wood lying on a table (14).
Specialized and hardware stores sell universal woodworking machines, as well as devices that allow turning. Thus, on the universal woodworking machine UBDN-1 TsZ it is possible to perform turning operations with workpieces with a diameter of up to 70 mm. There are attachments for wood turning in universal woodworking machines, models UBDN-1, MP-8-876, etc. However, stationary lathes (with a large number speed of electric motors and high power). In some cases, when it is necessary to turn parts of short length and small diameter, you can also use an electric drill (Fig. 2). The electric drill is secured in a vice with felt pads. A shank with a faceplate disk screwed onto it is inserted into the drill chuck. The vice is attached to the corner carpentry workbench in such a way that the tool rest is clamped in the carpenter's workbench (the tool holder is made to the required width and thickness). If used regular table, then the holder is secured to the table using a clamp. On such an improvised lathe you can carry out boring and turning shaped surfaces. When installing the tool rest, you must ensure that it is installed strictly along the axis of the chuck, at the appropriate height (relative to the center of the faceplate) and at a certain distance from the workpiece.
Rice. 2. Electric drill machine:
1 - carpentry workbench; 2 - rotary bench vice; 3 - hand-held electric drill;
4 - faceplate; 5 - tool rest; 6 - carpentry workbench vice; 7 - tool holder
For similar devices would be better suited a drill that has a device that changes the number of revolutions of the rotating shaft (electric drill brand IE-1036E).
In order to turn parts of various shapes, you must, of course, have appropriate devices for gripping and securing workpieces on a lathe. The main ones are chucks, which are screwed onto the machine spindle on one side and hold the workpiece on the other. Depending on the shape of the turned product and the size of the workpiece, the fastening method is also selected.
Most often, wood is processed in centers, when on one side the part is fixed in a trident, and on the other it is pressed by the center of the tailstock of the lathe (Fig. 3, A). Parts ranging in size from 30 to 100 mm are processed in this way. A chuck with a pyramidal hole is used to grip thinner workpieces (Fig. 3, B). Such a lathe chuck can be made by a craftsman himself from hardwood.
Rice. 3. Devices for securing workpieces - lathe chucks:
A - trident cartridge; B - pyramidal lathe chuck; B - faceplate with points: 1 - faceplate; 2 - detail; 3 - axial fastening center; 4 - quill with a retractable tailstock cone; G - faceplate with an additional wooden disk: 1 - faceplate; 2 - glued disk; D - vice chuck; 3 - tubular lathe chuck with screw clamps (8 pieces); I - three- and four-angled lathe chucks: 1-3 - methods of fastening workpieces in jaw chucks; K - mount screw pair: 1 - cam chuck; 2 - detail; 3 - screw with nut; L - clamp on a wooden mandrel: 1 - mandrel; 2 - ring (detail); M - steady rest: 1 - frame; 2 - fastening screws; 3 - riser.
A disc-shaped wooden workpiece in which axial turning is not expected internal cavity, are also attached in the centers, only instead of a trident they use a faceplate with pointed points (Fig. 3, B). This device is also easy to make: drill holes in a regular metal faceplate, cut threads in them and, screwing the screws in, sharpen the heads of these screws. The length of the tip is about 4 mm. After turning the required shape, the part is removed from the chuck, and the fastening auxiliary axial center is cut off from the lathe with a sharp knife. It is convenient to fasten disc-shaped workpieces to the faceplate using screws. In order not to damage the surface of the part when clamping, an auxiliary disk made of low-value wood is glued to it - pine, linden, etc. Screws are screwed into this disk (Fig. 3, D). After turning it is disconnected.
If the part does not require internal turning in the central part, it is secured using a screw device (Fig. 3, E). Even a large screw is suitable here if you saw off its head and cut a thread on its cylindrical part with a die, and then screw it in the center into the faceplate. Small parts are secured with a one-sided grip in cylindrical chucks (Fig. 3, E). For holding workpieces in lathe chucks similar design the protrusion of the part is pre-sharpened (for placement in the chuck hole).
When processing faceted surfaces, a vice lathe chuck is used (Fig. 3, G). Here the part to be turned is inserted into the vice of the lathe chuck and clamped with a screw.
A cup lathe chuck is the same cylindrical one, where there are several located around the circumference of the metal cup. threaded holes, into which studs are screwed, having a tetrahedral head for a socket wrench at one end (Fig. 3, 3). A cup chuck clamps workpieces with a significantly larger diameter compared to a cylindrical chuck. Lathe chucks with jaw clamps are also very convenient. There are three- and four-jaw lathe chucks. When the lathe chuck key rotates, all the jaws are compressed simultaneously, so that the workpieces are secured securely and quickly. In Fig. Figure 3 shows three methods of fastening parts in a three-jaw lathe chuck.
To turn rings, use a device consisting of a three-jaw lathe chuck, into which is clamped a rod that has a thread at the end onto which a nut is screwed (Fig. 3, K). In addition to those mentioned, there are other devices for processing workpieces with a central through hole. How ring-shaped blanks are pressed onto a wooden frame is shown in Fig. 3, L.
The list of clamping devices could be continued, since there are many ways to fasten workpieces of different configurations. Among the auxiliary devices, the stand-rest should be noted (Fig. 3, M). It is used when processing long and thin turning products to eliminate vibration during operation. But it is necessary that the center of the device is on the same axis with the spindle of the lathe.
Cutting tool
Turning parts on a lathe is done with a hand-held cutting tool. A distinction is made between rough and fine turning. Hence the choice of cutting tools (semicircular chisels - reiers, flat chisels - meisels, gravers and hooks). Using semicircular chisels (rearers, Fig. 4, A) the surface of the part is pre-treated.
After the semicircular chisel, a flat finishing chisel is used - a jamb (Fig. 4, B). This is a knife with a blade sharpened on both sides at an angle of 20-25°. This sharpening makes it possible to work from the middle of the blade - in the case when convex or straight surfaces are subject to sharpening. The ends are cut with an acute angle, and the roundings of turning products are turned with a blunt angle.
A flat chisel can be made from a regular chisel, from a flat file (with the notch removed), etc. For finishing of grooves with a straight bottom, narrow chisels are used - chisels - like a narrow carpenter's chisel (Fig. 4, B). To ensure the strength of the cutting tool, its thickness is made 2-3 times greater than its width. It has a one-sided sharpening, with a sharpening angle of up to 25°. To obtain deep grooves, the width of the rod from the blade to the tool handle must decrease. To side walls make the grooves smooth, use the sharpening form shown in Fig. 4, G. In Fig. 4, D shown turning tool, two blades of which intersect on the axis of the rod at an angle of 60-70°. It removes relatively narrow chips, which is most suitable for pre-turning. With this cutter you can make grooves with a triangular profile and chamfer. Shaped or fillet chisels have a rounded blade and are designed for turning internal curved surfaces (Fig. 4, E). Instead of flat shaped cutting tools, chisels with a bent blade - hooks - are sometimes used (Fig. 4, G).
Turning of internal cylindrical and conical surfaces carried out using a beveled corner chisel, internal corner which approaches 80° (Fig. 4, 3).
Shaped and corner chisels there are left and right. Chisels for turning balls are shown in Fig. 4, K. For the manufacture of parts of increased complexity, crossbars are used. Several individual cutters are inserted into a special metal case, onto which several clamps are placed (to clamp the tool) and secured with screws. When turning a large number of identical figures, combs are used for marking, and figured cutters with blades are used for turning complex profiles.
For drilling holes, spoon screw drills are used, and for smoothing out the ridges of micro-irregularities, files (as for metal work) with a coarse notch are used. When processing wood by turning, in addition to cutting tools, carpentry and locksmith tool- tape measure, squares, folding meter, carpenter's compass, calipers, etc. Check complex profiles with templates.
Turning material
Both hardwood and conifers wood - it all depends on the purpose. Conifers are used mainly for furniture. Medium and small turning parts are made mainly from hardwood wood: birch, ash, linden, walnut, beech, oak, hornbeam, mahogany, pear, apple, poplar, aspen, alder, Karelian birch, boxwood. Floating hardwoods are highly valued in turning. Some shrub species of wood are also used here - barberry, hazel, sloe, mulberry stems, juniper tea rose, etc.
In addition to wood, ebonite, bone, horn, amber, mother-of-pearl, etc. are used for turning.
Preparing wood for turning
Wood blanks must have an allowance for processing and, if possible, a shape close to the sample with an allowance for trimming (facing) and for clamping in a lathe chuck. Under-dried wood gives a fleecy surface when turned, while over-dried wood, having increased fragility (especially with a long piece and small diameter), can break.
The processing allowance for wooden workpieces is determined by its length, surface condition, clamping device, processing method. So, when installed in cup and jaw chucks, the length allowance should be about 60 mm, and when using a trident and on a faceplate - 25 mm.
In the case of hardwood, when processing wooden workpieces, preliminary drilling is done in the centers under the center (under the quill cone). Applicable wood material must be free of defects - cracks, knots, rot, etc. The log for the workpiece is first cut with an ax, removing the bark, and adjusted to the shape of the future turning part. Often, in addition to an ax, a plow is also required (Fig. 5). Typically, for small and medium-sized products, the shape (if turning is along the length) is made cylindrical. And for large turning products, the workpiece is often glued together. In this case, in order to avoid any complications caused by the influence external environment(cracking, warping, etc.), you should select material of the same type or properties.
Fig.5. Strug
Working on a lathe
Turning makes it possible to obtain not only a cylindrical and complex-profiled surface, but also round, wavy, twisted, flat-relief, rectangular, oval and other varieties. But this is subject to successful mastery of turning techniques. The sequence of operations during turning is always the same, only the tools, fixtures and turning techniques change. The main operations are: installing a wooden workpiece in a lathe chuck or in centers, giving the tool rest the required position, cylindering (rough turning), marking groove, finishing turning and trimming the ends, rounding the ends, removing allowance. In this case, you must adhere to some rules:
the position of the tool rest and working methods are determined by the shape of the wooden workpiece and the direction of the wood fibers;
when manufacturing turning parts with a diameter of up to 100 mm with a longitudinal grain direction, the support should be located slightly above the center line of the centers;
when turning disc-shaped parts, the tool rest is located below the center line;
when fastening the material of a wooden workpiece in a trident, the latter is removed and the workpiece is stuffed onto a rigid base;
The correctness and reliability of fastening the wooden workpiece should be checked a few minutes after starting work by stopping the machine and checking the fixation of the blank.
It is also important to hold the cutting tool correctly.
The turning chisel is held with two hands: one by the handle, the other by the shaft of the tool. The right hand balances the cutting force, while the left hand presses the cutting tool to the tool rest and performs a longitudinal feed.
One of simple operations is the turning of cylindrical shapes. The wooden blank is fixed in a trident chuck. The loose end is pressed with the tailstock quill cone. Then install the tool rest so that it is approximately 4 mm from the processing surface, above the center line. First, the wooden workpiece is scraped with a semicircular chisel, not with the central part of its groove, but at an angle of 15° to the axis of rotation of the wooden workpiece in the direction of feed, that is, with a section of the cutting tool located one third of its edge. You should not take chips thicker than 2 mm. The force of the hand holding the cutting tool from above, as well as the feed, must be constant. It is also necessary to ensure that the wood is not pulled out. During the first passes, the straightness of the surface is checked with a carpenter's square. Subsequent control is carried out using calipers. Removing chips on the last passes, forefinger The left hand is held under the shaft of the chisel to move it smoothly along the surface of the turning workpiece. The thickness of the chips from the last pass with a semicircular chisel should not exceed 1 mm. After this, finishing turning is carried out using a flat chisel. For finishing, meisel up to 25 mm wide is recommended. The tool rest is moved closer to the wooden blank. The cutting tool is held so that the obtuse angle of the chisel is at the top and the sharp angle at the bottom, otherwise the chisel will vibrate, picking up the fibers.
After finishing, the ends are trimmed - first the right one. Trimming is done until the diameter of the rod is 13 mm. Then the second end is trimmed: the tool is pressed against the tool rest with the right hand, and guided with the left. To avoid excessive waste of wood, it is better to use a narrow chisel when cutting.
It is more difficult to turn a cone than a cylinder. The tool rest is installed at an angle to the axis parallel to the shape of the future cone (Fig. 6). The blank is pre-treated with an ax. The workpiece is secured with its apex to the clamping chuck. Turning of conical shapes should be smooth, without jerking, with uniform pressing force and uniform feed. Measurements of the workpiece must be done more often than when turning a cylinder. When finishing, this is especially true in the area near the tip of the cone.
Rice. 6. Turning a cone
Straight cutting is a combination of cylinder and cone shapes. Here, control templates are used, as in general when making complex surfaces. When turning parts with identical threaded shapes, a template is made for only one section. If there are several sections, then the same number of templates is required. Templates are used only for finishing turning. They are made from thin plywood or hard cardboard, and for particularly complex work - from galvanized iron. When cutting straight, first mark the distance and determine the extreme end, and then carry out the marking according to the drawing. At the same time they produce required amount templates Turning is carried out as follows: a flat chisel is used to make a groove, making triangular cuts. Excess material is removed with a slightly larger chisel, then control is carried out with a template and, if necessary, the edges of the side surfaces are trimmed. After grinding the entire surface, trim the part according to the drawing.
Performing curved cutting of rollers and fillets is distinguished by turning disks with oval edges and fillets (Fig. 7). A fillet is two disks connected by a curved surface of a certain radius. First, the cylindrical surface is turned, and then the fillets, for which they make a disk, make an oval and make the central part of the fillet - a semicircle - as follows: mark the center of the disk with a pencil, and then along the marking line, first to the right and then to the left, make roundings with a semicircular chisel, then Then the tool rest is rearranged at an angle to the axis of the turning product and, with a flat chisel, first one and then the other half of the roller is ground. To do this, the tool rest is accordingly rearranged in the direction from which turning occurs. Control is carried out periodically using a template. The groove is carried out with a chisel from top to bottom, without lifting the cutting tool from the ridge of the tool rest. Finish turning the fillet part by trimming the ends.
Rice. 7. Curvilinear cutting
Rice. 8. Complex Rectilinear cutting is a combination of cylinder and cone shapes. Here, control templates are used, as in general when making complex surfaces. When turning parts with identical threaded shapes, a template is made for only one section. If there are several sections, then the same number of templates is required. Templates are used only for finishing turning. They are made from thin plywood or hard cardboard, and for particularly complex work - from galvanized iron. When cutting straight, first mark the distance and determine the extreme end, and then carry out the marking according to the drawing. At the same time, the required number of templates is produced. Turning is carried out as follows: a flat chisel is used to make a groove, making triangular cuts. Excess material is removed with a slightly larger chisel, then control is carried out with a template and, if necessary, the edges of the side surfaces are trimmed. After grinding the entire surface, trim the part according to the drawing.
Performing curved cutting of rollers and fillets is distinguished by turning disks with oval edges and fillets (Fig. 7). A fillet is two disks connected by a curved surface of a certain radius. First, the cylindrical surface is turned, and then the fillets, for which they make a disk, make an oval and make the central part of the fillet - a semicircle - as follows: mark the center of the disk with a pencil, and then along the marking line, first to the right and then to the left, make roundings with a semicircular chisel, then Then the tool rest is rearranged at an angle to the axis of the lathe and with a flat chisel, first one and then the other half of the roller is ground. To do this, the tool rest is accordingly rearranged in the direction from which turning occurs. Control is carried out periodically using a template. The groove is carried out with a chisel from top to bottom, without lifting the cutting tool from the ridge of the tool rest. Finish turning the fillet part by cutting the end profile of the cone-shaped part
Sometimes the shape of the profile parts contains a cone (Fig. 8). Such a part begins to be turned from a cone, and then each section is turned according to the markings, rearranging the tool rest and changing the cutting tool, as well as controlling the size with templates. If in parts being machined into a cone, the surface of a complex profile has sharp edges (as when turning fillets with a spherical notch), then these notches are first cut using hooks. All other operations are repeated in the sequence described above. The production of the part is completed by trimming the ends.
Round turning is essentially a combination of techniques learned previously.
The workpiece is first made cylindrical, and then a semicircular chisel is shaped with an allowance for processing. Control is carried out using calipers. Finishing is carried out with a flat chisel, and control is carried out with a template made of galvanized iron (a plate with a cut out semicircle of a ball slightly larger than the calculated one). Having attached the template to the ball, grind down those places where the template comes into contact with the wood of the workpiece. Having removed the turning workpiece with the ball from the machine, they cut off the excess wood in the places of the necks and clean the sawing places with a small file and sandpaper, and then polish the ball with glass sandpaper.
Turning a ring is not a very complicated operation, but it does require attention. There are several ways. Here's one of them. First, give the workpiece cylindrical shape and carry out finishing, then mark on it the number of rings in width, leaving an allowance for trimming (trimming). For each ring, a groove is made with a shaped cutter in the internal cavity, butted on one side and cut off. But these are not rings yet. It is necessary to further process their upper oval surface in a lathe chuck - a journal. Here the part is marked for shaped grooves, sharpened and polished. The ring is then knocked off the trunnion and trimmed.
Hollow volumes are machined from blanks in the shape of a cylinder. In this case, only the headstock chuck (usually a cam chuck) is used. First, the inner, then the outer cylindrical surface is made.
Significant recesses are made as follows: drill a center hole with a drill installed in the quill of the tailstock of the machine, or with a semicircular chisel, which is supported on a tool rest placed slightly below the center line. The ovality of the internal surfaces is obtained using a suitable flat chisel. Deep cylindrical recesses are made using a holder with replaceable or adjustable cutters installed in the tailstock quill. After drilling center hole using a large-diameter drill, a tool holder with a cutter having cutting edges at both ends of the front edge is inserted instead (Fig. 9). Each pass is made with a longer cutter.
Rice. 9. Tool holder for turning internal cylindrical recesses of large diameter:
For disc-shaped wooden blanks, appropriate species are selected. On one side, the board must be processed with a jointer - here the markings are made with a compass. Workpieces of this kind are processed on faceplates. A cut wooden blank in the form of a circle with the necessary allowance is marked for the mounting holes on the faceplate and for the faceplate itself (Fig. 10). First, peeling is performed in the axial direction, and then in the radial direction. After rough processing, the rough surface is refined with a semicircular or flat chisel (with a one-sided sharpening chamfer). With a semicircular chisel placed horizontally on a tool rest, only the central part of the blade cuts. Concave or convex shape The disc-shaped wooden workpiece is shaped using semicircular or special shaped cutters. To obtain a smooth surface, the feed is carried out: when turning convex contours - from the center to the edge, and when turning concave contours - from the edge to the center.
Rice. 10. Turning disc-shaped blanks:
Surface finishing is carried out using finishing chisels (see Fig. 4, K).
Steady rests are used to cut identical small parts, such as balls, from a long cylindrical piece of wood. The support is installed as shown in Fig. eleven.
Rice. 11. Use of a steady rest when turning:
Finishing of turning products
After finishing turning, the product, without removing it from the lathe, is ground with abrasive sandpapers of different grain sizes. At the same time, the spindle speed of the lathe is reduced: the abrasive grains cut into the wood better and the product is sanded faster. The support is removed.
It is not recommended to wrap the sandpaper around a turning product. For hard rocks, fine-grained sandpaper No. 6-10 is suitable, and for soft rocks - No. 10-16. It is necessary to ensure that edges, protrusions and other sharp edges are not worn off. Pumice is also used for grinding turned products: cotton cloth is moistened with linseed oil or drying oil and sprinkled with pumice powder. Grinding of the cylindrical surfaces of the product is carried out using sanding paper stretched over smooth boards. After grinding, the turned product is wiped with a piece of cloth, then polished with polishes. If desired, turning products are tinted, ornamental compositions are burned onto them, and they are inlaid. They are also decorated with wood mosaics, paintings, carvings, etc. All types of wood finishing are suitable for turning products.
Turning products that have independent significance are polished without removing them from the lathe - with leather or dry horsetail, horsehair, etc.
Polishes are applied with wool or cotton swabs. The tampon is refilled through several passes, and if the turning product is large (table leg, baluster, etc.), then more often. When polishing, the tool rest is removed from the bed.
Small turning products are not polished, they are varnished. The varnish should not be thick. It is applied with a brush or swab. Before varnishing, coat the turned product well with hot aqueous solution wood glue, and after it dries, clean it thoroughly. The varnish is applied twice - the second time after drying.
Turning products are also coated with wax mixed with turpentine (or Galosh gasoline) - 5:1. The mixture is applied hot (heated in a water bath) to the surface to be treated. When it has cooled slightly, turn on the lathe and rub the product with a cloth until it shines. Painting of turning products is done with a preliminary primer with white diluted in drying oil (preferably natural, linen). After the primer has dried, paint is applied evenly with a brush, usually in several layers.
Safety precautions when working on a lathe
Turning on a lathe requires constant attention and compliance with safety rules. Before operation, the lathe must be thoroughly lubricated and the serviceability of its parts must be checked, especially the insulation of the rotating components and the electric motor.
When starting to work on a lathe, it is necessary to securely secure the wooden workpiece in the lathe chuck or in the centers, pressing it with the tailstock. The workpiece is balanced with the machine turned on. The support bracket of the tool rest is installed no further than 4 mm from the surface to be machined, and the tool rest is periodically moved towards the lathe (as the allowance layer is removed from the workpiece).
The tool rest is installed either at the level of the axis of rotation of the turning workpiece, or slightly higher. Otherwise, the cutting tool will tear and scrape the surface, resulting in roughness. To avoid breakouts, periodically check the reliability of the clamping with the center of the tailstock, where the socket is broken with a cone and the clamp is loosened. Correct position hands when turning is the key to success. The cutting tool should be held on the support bracket of the tool rest with the entire palm of the left hand, and not pressed only with the thumb, covering the support bracket of the tool rest from the sides with the rest. The right hand grips the handle of the cutting tool and directs its movement. Uniform, without jerking, pressure on the base of the tool rest and on the part is very important. It is recommended to work in safety glasses, neatly tucked clothes, and a hard apron; control should be carried out only after stopping the machine.
It is unacceptable to use cutting tools with defects - chipping, cracks, bends. It is strictly forbidden to allow children and persons unfamiliar with its structure to work on the machine. The lathe must not be used for other purposes.
Turning of some products
Having mastered the basic techniques of turning, a novice craftsman will naturally first take up the manufacture of the simplest turned products - cylindrical ones. These could be handles for tools, pegs for hangers, bowling pins, stands for table lamp etc. For example, consider the technology of turning a peg for a hanger. Suitable material for this part is birch. You can make several pegs from one piece of wood. You can use a comb for marking.
The wooden blank is ground with a rake and a meisel to the required diameter, and then the part is marked. Having trimmed and sanded the part, it is cut off with a chisel after stopping the lathe. Tool handles are made in the same way, with the only difference being that the contour of the handle, due to the curved surface, is controlled with a template.
Bowling pin - more complex figure. The shapes of a cylinder, cone, rounded disk and ball are combined here (Fig. 12). First of all, a wooden blank (1) is turned and the surface is finished according to largest diameter. Then markings are made with a comb or compass with an accuracy of 0.3-0.4 mm. The conical element (5) is made with a small allowance for grinding. Next comes the cylindrical element (3), the roller (4), the transition cone (2) and, finally, the ball head (6). When turning a spherical surface, you must adhere to the dimensions indicated in the figure and often check the shape of the ball using the template. The material for making bowling pins can be beech, walnut, or pear. After turning all the shapes, the part is sanded and cut from a wooden blank. If the texture is weak, the bowling pin can be painted.
Rice. 12. Making bowling pins:
1 - turning blank; elements:
2 - truncated conical;
3 - cylindrical;
4 - disk with oval edges;
5 - conical;
6 - ball head bowling pins
Flower stands in the form of a table with a turned leg and legs are made from valuable species- oak, beech, walnut, ash, chestnut, etc. (Fig. 13). Using a faceplate with sharp points, the top cover is made. Then, having removed the cover from the faceplate, mark the location of a hole with a diameter of 30 mm in it, and use a drill head to drill it on a tabletop drilling machine. A regular screw drill is attached to the center of such a head for centering, and three cutters cut out the required diameter.
It is better to turn the table stand (turned leg) in a cam lathe chuck with the part pressed by the tailstock. As usual, we start by obtaining a cylindrical piece of wood. Then, along the marking lines made with a compass, cylindrical surfaces (85 mm in diameter), conical surfaces, disks (135 mm in diameter), fillets (neck diameter 35 mm), a cone-shaped bevel (length 60 mm) and bosses ( diameter 30 mm).
All fillet work is also carried out. After grinding, remove the wooden piece supporting the head on the right from the lathe, and cut off a part of the boss 25 mm long that protrudes on the left. The boss should be made with allowance for a tight fit of the lid on it. After turning operations, spreaders are made from the boards. Having marked and hollowed out three symmetrical holes in the rack at an angle of 120° to each other, insert the legs into these holes, lubricating the joints with epoxy glue. After cleaning the places where the legs are attached, a cover is put on the stand, and the entire turning product is coated 2-3 times with nitro varnish (brand NTs-222 or NTs-218). Colorless varnish (AK-156 brand) or oil varnish is also suitable.
In Fig. 14 gives profiles of semicircular frames for mirrors and paintings small sizes, as well as a drawing of the frame for the mirror. The frames are mostly made of thick boards or glued pieces of wood of the same type. The width is determined on the faceplate - the wooden blank is trimmed, then it is turned along the width (diameter 90 mm). Having rearranged the tool rest, they make a selection from one end to fit the mirror (glass, picture). Having made the groove, the wooden workpiece is rearranged, secured in a cam lathe chuck by the groove, and a through hole is machined from the end. The final operation is to give the frame an oval shape using a special cutter. Profile control using a template. This is followed by grinding and polishing.
Rice. 14. A - profiles of rounded frames for small paintings and mirrors.
B - drawing of a rounded frame
Rice. 15 - hanger, consists of individual elements strung on a metal tube. On the head of the hanger there are two rows of turned pegs inserted into the holes. The base is on a support made of spherical stands. The base is sharpened on a faceplate, constituent elements- in jaw lathe chucks, head, pegs and balls - in the centers.
Rice. 15. floor hanger for clothes
The page uses materials from -http://rezba-dereva.narod.ru/tokarnie-stanki.htm
The surfaces of molds and some dies are subject to high demands in terms of smoothness and cleanliness, but slightly larger deviations from the geometric shape and dimensional accuracy are allowed than, for example, with measuring tools.
When processing such surfaces, finishing turns out to be too expensive an operation and therefore they resort to polishing. A characteristic feature A well-polished surface is characterized by its mirror appearance and the absence of noticeable marks. The polished surface is more resistant to mechanical wear and chemical exposure to various components of the pressed materials.
The polishing process can be carried out either on machines or manually using electrified or pneumatic tools. Polishing is also carried out with elastic wheels and tapes using soft finishing materials. Before polishing, the surface is ground with elastic wheels and tapes, onto which hard, abrasive-finishing materials are glued.
Wheels for elastic grinding and polishing are made of wood, felt, leather, felt and other materials. Felt and felt wheels come in different densities, with denser wheels used when processing parts that have sharp corners. For preliminary elastic grinding, wooden polishing pads wrapped in abrasive sandpaper can be used. Abrasives are glued onto the working surface of flexible wheels using hide or casein glue.
Abrasive materials for polishing are: GOI paste, chromium oxide, crocus, Vienna lime and quartz. These materials are applied to the surface of the wheel in the form of pastes consisting of 70-80% abrasives and 20-30% binders - stearic and oleic acids, paraffin, technical lard, rosin, kerosene and mineral oils. The higher the polishing speed, the thicker the consistency of the pastes should be.
Polishing performance depends on the pressure of the part on the wheel. Typically, for unhardened steel this pressure ranges from 2.5 to 5 kg and for hardened steel from 2 to 2.5 kg.
Polishing is carried out at a peripheral speed of 30-35 m/sec, grinding with elastic wheels - at a speed of 18-30 m/sec, and the finer the grains of the abrasive material, the higher the peripheral speed.
Elastic grinding is usually carried out on lathes and drilling machines using wooden polishing pads with abrasive sandpaper (Fig. 63). The end of the tape cut from the roll of skin is inserted into the slot of the mandrel, and the tape is screwed onto the mandrel. To avoid local unevenness on the machined surface, work is carried out with continuous reciprocating movement of the spindle and the workpiece in the directions indicated in the figure. These movements are performed manually.
Fig. 63. Elastic grinding on a drilling machine.
The described grinding process with abrasive sandpaper is used only if surfaces with a free exit for the end of the polishing pad are subjected to processing. Otherwise, grinding is carried out with flexible wheels and heads using hard abrasive finishing materials. Wheels and heads made of hard wood and textolite with abrasive pastes are also used.
Final polishing is carried out using felt wheels with pastes made from soft finishing materials.
Finishing operations are performed to improve the cleanliness, precision of processing, or to create a specially designed roughness of a certain pattern on the surface of a part. For this purpose, filing, polishing, finishing, fine turning, rolling, rolling, smoothing and rolling are performed on lathes.
§ 1. Filing
Purpose. Filing is carried out to clean surfaces, remove burrs, remove small chamfers, and also to cut off a small layer of metal when the diameter after grinding is larger than required.Tools. Filing is done with files various shapes: flat, square, triangular, round, etc. For rough work hog files are used, for finishing - personal files and, if necessary, to obtain a high surface cleanliness - velvet files. They differ from each other in the number of notches on equal to length.
Before use, files should be inspected and, if necessary, cleaned of dirt and shavings with a wire brush, moving it along the notches. Oily files are first rubbed with a piece of dry chalk or charcoal.
Working methods. To prevent injury, filing on a lathe should be done carefully and carefully. Only use files with a tightly fitted handle. During filing, the turner should stand at approximately an angle of 45 to the right to the center axis of the machine. The handle of the file is clamped in the left hand, and the opposite end is held with the fingers right hand(Fig. 198),
During the filing process, the file is placed perpendicular to the axis of the part, lightly pressed against the surface to be processed and smoothly moved simultaneously forward and to the side. When moving backwards, release the pressure slightly. Fast and sharp movement of the file disrupts the shape of the part. The pressure on the file should be the same throughout 
its progress, otherwise the removal of metal will be uneven, which will lead to distortion of the shape of the treated surface.
Operating mode. The peripheral speed of the processed surface during filing is assumed to be 15-20 m/min.
§ 2. Polishing
Purpose. Polishing is performed to increase the cleanliness and shine of surfaces, as well as to prepare them for electrolytic coating with chromium or nickel.Tools. On lathes, polishing is carried out using sandpaper on paper or canvas. Steel and non-ferrous ductile metals are treated with corundum skins, cast iron and brittle materials - with silicon carbide skins. The grain size of the sandpaper (the size of the abrasive grains in hundredths of a millimeter) is taken depending on the required cleanliness of the surface being treated within 50-3;
Working methods. A piece of skin is held with the fingers of the right hand or with both hands at its ends (Fig. 199, a),
are applied to the rotating part and moved back and forth along the polished surface. You cannot hold the skin with your hand, as it can wrap around the part and pinch your fingers.
When polishing, stand at the machine in the same way as when filing, approximately at an angle of 45° to the right to the axis of the centers of the machine. The front end of the skin is held with the left hand, the opposite end with the right.
Polishing is performed sequentially with several sandpapers with a gradual decrease in their grain size.
It is convenient to polish cylindrical surfaces with a squeegee (Fig. 199, b). They consist of two wooden blocks connected at one end by leather or a metal hinge. Sanding paper is placed in the inner radius recesses of the bars. The surface to be treated is covered with a press, which is held by hand, and polishing is performed using actions similar to those described above.
When polishing, the part becomes very hot and elongates. Therefore, when it is pressed by the center, you need to periodically check how tightly it is clamped and, if necessary, loosen it a little.
Operating mode. To obtain the best surface cleanliness, the number of revolutions of the part should be as high as possible. During final polishing, it is recommended to lightly lubricate the surface of the part with oil or rub the sandpaper with chalk.
§ 3. Fine turning
Purpose and essence. External and internal surfaces are processed with fine turning with an accuracy of 1-2 classes and a cleanliness of 8-10 classes. This type of processing in many cases can replace grinding.;Its essence is to cut off a small layer of metal with a very low feed and high cutting speed.
Requirements for machines for fine turning. Machine tools must be rigid, precise (radial runout of the spindle no more than 0.005 mm), high-speed (revolutions no less than 2000 rpm) and have feeds less than 0.1 mm/rev. Limbs or indicator stops must allow the installation of cutters to size with an accuracy of at least 0.01 mm.
Without resorting to special devices, the accuracy of the cutter feed to the depth of cut on any lathe can be increased by using the dial of the upper slide, rotated at a certain angle and the axis of the centers of the machine (Fig. 200). If we take t - the amount of movement of the cutter in the angular direction, and t\ - perpendicular to the axis of the part, then the required rotation angle of the slide a can be determined from the formula
Example. When the upper slide dial division price is 0.05 mm, it is necessary to increase the accuracy of the cutter movement to the cutting depth to 0.01 mm. Determine the angle of rotation of the upper slide.
Solution. In this case /i=0.01 mm, t=0.05 mm,
According to formula (27)
The cutters used. Cutters for fine turning are equipped with hard alloy plates of grades VK2 or VKZM for processing cast iron and T30K4 for steels. Diamond cutters are used for non-ferrous metals and plastics.
After sharpening, the cutters must be sharpened. home cutting edge
should be sharp, without chamfer. Debris or minor nicks on it are unacceptable.
The top is rounded with a radius of 0.5-1 mm:
The rake angle for carbide cutters when processing steel is from -5° to +5°, for cast iron - 0°. For diamond cutters when turning y = - 4°, when boring y = 0°. The rear angle is within 6-12°.
Allowances and cutting modes. The allowance for fine turning is left in the range of 0.25-0.4 mm per diameter for part diameters up to 125 mm.
Cutting conditions are usually limited by the capabilities of the machine. They are recommended to be selected within the following limits: cutting depth 0.05-0.2 mm; feed during preliminary processing is 0.1-0.2 mm/rev, during final processing - 0.02-0.08 mm/rev; cutting speed for ferrous metals is 100-200 m/min, for non-ferrous metals - 200-500 m/min.
§ 4. Finishing
Purpose and essence. Surface finishing is carried out to increase their accuracy to grades 1-2 and cleanliness above grade 9.During the finishing process, using special lapping tools saturated with abrasive powders or pastes, the smallest irregularities are removed from the surface of the part, as a result of which it acquires the necessary accuracy and cleanliness.
Abrasives and binding materials. The working surface of the lap is saturated with abrasive powders or pastes. For this purpose, abrasive materials are used: electrocorundum powders for finishing steels and silicon carbide for cast iron and other brittle materials.
The granularity of the powders is selected depending on the required purity of processing. Rough finishing with a purity of V9-V1O is carried out using grinding powders with a grain size of 5-3, preliminary finishing with a purity of up to V 12 - with micropowders M40-M14; finishing with purity up to V 14 - micropowders M10 - M5 (for micropowders, the grain number corresponds to the grain size in microns).
Of the finishing pastes, GOI pastes are the most widely used. They contain a soft abrasive material - chromium oxide (70-85%), as well as active chemicals and binders. They are used for finishing steel and non-ferrous metals.
According to their finishing ability, GOI pastes are divided into coarse, medium and fine.
Kerosene or mineral oils are used as binders and lubricants during finishing.
Lapping. They are bushings with a longitudinal cut, allowing them to be adjusted in diameter to compensate for wear. For small diameter holes, non-adjustable laps are used: in the form of a round rod.
Final finishing is carried out by lapping with smooth surface(Fig. 201, a). Lappings for preliminary finishing (Fig. 201, b and c) are equipped with longitudinal or helical grooves in which they are assembled
residues of abrasive material during operation.
Lappings 3 for processing holes have conical hole with a taper of 1:50 or less often 1:30. They are installed on mandrel 1 with the same taper (Fig. 201, d) and can be adjusted in diameter due to axial movement with nuts 2 and 4. Lappings 3 (Fig. 201, e) for finishing the shafts are installed in clamps 1 and adjusted with screw 2 .
The lap material is selected depending on its purpose and. the abrasive material used.
When finishing with hard abrasive materials, the grains of which are pressed into the lap, the material of the latter must be softer than the material of the workpiece. In addition, the larger the grains of the powder used, the more you should choose soft material for lapping.
For rough finishing, laps made of mild steel, copper, bronze, brass are recommended, and for preliminary and finishing - from fine-grained gray cast iron of medium hardness (HB 140-170).
To work with soft abrasive materials (pastes based on chromium oxide, iron oxide, GOI pastes), the grains of which do not sharpen, the lap must have a greater hardness than the part being finished. In this case, good results are ensured by the use of laps made of hardened steel or gray cast iron of increased hardness (HB 200-220).
Lappings are manufactured with high precision. Their geometric shape errors should not exceed 0.005-0.01 mm.
To prevent jamming during the finishing process, the diameters of the laps should provide some clearance in connection with the part. The following gaps are recommended: for rough finishing - 0.1-0.15 mm, for preliminary finishing - 0.03-0.06 mm, for finishing - 0.005-0.01 mm.
Preparing the lapping for work. Saturation (caricature) of the lap surface with hard abrasive materials is carried out directly or indirectly.
With the direct method of caricature, the surface of the lap is slightly moistened with kerosene or oil and evenly sprinkled with a thin layer of abrasive powder. The abrasive grains are then pressed into the lap by rolling it over a hardened steel plate or rolling it with a hardened roller.
The indirect method of caricature is simpler, but less effective. In this case, abrasive powder is sprinkled onto the lubricated surface of the lap, which is sprayed during the finishing process.
GOI paste is thickly diluted with kerosene and applied in an even thin layer to the surface of the lap.
Preparing the part for finishing. The surface of the part must be processed for finishing by finishing, fine turning or grinding. The smaller the allowance left for finishing, the more accurately and quickly you can maintain the required size and cleanliness of processing. For finishing, it is recommended to leave an allowance of 0.01-0.03 per diameter.
Finishing techniques. When finishing the outer cylindrical surfaces, the workpiece is fixed in the chuck or in the centers, and the lap is put on it and moved evenly and slowly by hand along the rotating part. As wear occurs, the lap is adjusted in diameter.
To tap holes, the lap is fixed in a spindle or chuck, and the part put on it is held by hand and evenly moved in longitudinal direction.
Additionally, the lap can only be saturated with abrasive powder or paste of the same grain size or coarser. Preliminary and final finishing are performed using different laps.
Finishing mode. The peripheral speed of the part or lap is assumed to be 10-20 m/min during preliminary finishing; during finishing, in order to reduce heating and expansion of the part, the speed is reduced to 5-6 m/min
§ 5. Hardening surface treatment by rolling, rolling and smoothing
Purpose. These types of processing are intended to strengthen the surface layer of the part, increase its wear resistance and improve the surface cleanliness to 8-10 classes. The process proceeds without removing chips due to smoothing the roughness obtained after turning.Tools. Rolling of external surfaces and rolling of holes is carried out by roller and ball rolling and rolling, smoothing is done with diamond tips.
Rolling with a symmetrical arrangement of the roller on two supports (Fig. 202, a) is used for processing external cylindrical and conical surfaces per pass. The roller has a spherical profile (Fig. 203, a). If it is necessary to process stepped surfaces, ledges, etc. of the ends, rolling is used with a one-sided roller arrangement (Fig. 202, b), the shape of the working profile of which is shown in Fig. 203, b, c and d. For running-
At the edges of the ledges and ends, the roller is positioned at an angle of 5-15° to the surface being processed.
The rollers are made of alloy steel X12M or 9XC and are hardened to a hardness of HRC 58-65.
Ball rolling and rolling (Fig. 202, c, d, e) are equipped with a spring, which ensures uniform pressure of the ball on the part. The required spring pressure, depending on the properties of the material being processed, is set with an adjusting screw. Such rolling and rolling allows one to successfully process non-rigid parts, since the ball, having point contact with the surface, does not need strong pressure. Running in (Fig. 202, c) is convenient for processing ends and ledges.
For running-in, balls from rolling bearings are used.
Diamond tips 1 (Fig. 204) are intended for smoothing the surface of the part. They represent a holder with a diamond, working surface which has a spherical or cylindrical shape. The tips are fixed in a cylindrical mandrel 2 and, together with it, installed in the housing 3. The required diamond pressure on the surface being processed is created by an adjustable spring placed inside the housing.
Preparing the surface of the part. The surface of the part is prepared by finishing turning for hardening treatment. The degree of roughness should be within 5-6 cleanliness classes. It is necessary to take into account that the diameter of the surface during the hardening treatment can change up to 0.02-0.03 mm. Therefore, the outer surfaces of the part should be made according to the highest limit
Size, and internal - the smallest.
Working methods. The strengthening tool, fixed in the tool holder of the machine, is brought close to the surface of the rotating part. A not strong, but fairly dense pressure is applied and in 2-3 reciprocating passes with mechanical feed the processing is carried out until the required surface cleanliness is achieved. To reduce friction and heating of the part, it is recommended to lubricate the surface being treated with oil.
Processing mode. Feed: when rolling with a ball - no more than 0.1 mm/rev, with a roller with a radius profile - 0.1-0.2 mm/rev. Diamond smoothing is performed with a feed of 0.03-0.06 mm/rev.
Product rotation speed 40-80 m/min.
§ 6. Rolling
Purpose. Rolling creates a specially designed roughness in the form of corrugations of a certain pattern on the surfaces of some parts (handles, screw heads, etc.).Tools and their installation on the machine. Knurling is carried out by knurling, consisting of a knurling roller and a holder (Fig. 205). To apply a straight pattern (Fig. 205, a) a single-roller knurling is used, and a mesh knurling (Fig. 205, b) is double-roller, respectively, with the right and left directions of the knurling.
Knurling rollers 1 are made of tool steels U1-2A or HVG and are hardened to a hardness of HRC 63-65. On the cylindrical surface of the rollers, corrugations are made by milling with a profile angle of 70° for rolling steel parts and 90° for parts made of non-ferrous metals. Depending on the diameter of the workpiece, the corrugations are arranged around the circumference in increments of 0.5 to 1.6 mm.
The knurling is fixed with the smallest overhang in the caliper tool holder so that the roller generatrix is positioned strictly parallel to the axis of the part. The check is carried out against the surface being treated using light. The axis of the single-roller knurling roller should be at the level of the center axis of the machine. For two-roller knurling, the accuracy of the height adjustment: is not significant, since in this case the rollers are self-aligned on the surface being processed due to the articulated connection of the holder 2 with the holder 3 (see Fig. 205, b),
Preparing the surface of the part for rolling. When rolling, the metal is squeezed out. Therefore, the surface of the part is ground for rolling to a diameter that is 0.25-0.5 less than the nominal corrugation pitch.
Rolling techniques. The rollers are brought close to the rotating part and, using manual transverse feed, are pressed into the surface to be processed to a certain depth. Turning off the rotation of the part, check the accuracy of the resulting pattern. Then turn on the spindle rotation and longitudinal feed and roll to the required length in several passes in both directions until full height corrugations.
It is impossible to move the rollers away from the surface being processed during the entire rolling process, since they may not fall into the previous grooves again and the knurling pattern will be distorted.
Knurling rollers should be periodically cleaned with a wire brush to remove metal particles stuck in the recesses.
Rolling mode. The longitudinal feed is taken to be approximately equal to twice the corrugation pitch (1-2.5 mm/rev), the rotation speed of the part is within 15-20 m/min. The surface to be treated is lubricated with oil.
