Lathe and turning*
A device for making bodies of rotation from wood and other hard materials, called a “lathe” (un tour, turning lathe, Drehbank), has been known since ancient times; only the “potter’s wheel,” used for making round clay vessels, is older than it. Turned products are found in abundance among Egyptian antiquities, and machines of a primitive design are still used in our time by different peoples. These machines are of two types: Asians, accustomed to squatting, also set up T. machines that correspond to this custom, and Europeans adapted them so that they can work while standing. On the table fig. 1 shows Hindus turning a column: an assistant brings the object being processed into an alternating rotational motion using a rope, like a spindle for making fire by friction. The machine itself consists of two pegs driven into the ground and a horizontal stick tied to them, serving as a tool, and the object being turned rotates on the tips of two nails. The Kalmyks also use a similar device, but they also have a more complex machine for turning cups (Table 2). Between the stakes fixed in the ground, a wooden semblance of a real “spindle” rotates with a neck and a thickening protruding behind it, which serves as a “cartridge” for attaching the piece being processed. To do without an assistant when processing small objects, the rope is pulled over a “bow”: then the master sets the work in rotation with one hand, and must hold the tool with the other. Such bowed machines are common among the Persians, Arabs, etc. In Europe, they preferred to indicate rotational movement with the foot: on the table. fig. Figure 3 depicts such a machine in the form in which it is now used for making wooden things in Italy, Switzerland and other places. Instead of stakes driven into the ground, there is a whole frame with two horizontal parallel bars, between which both “headstocks” with points for the object being turned are moved and secured with wedges. Instead of a bow, an elastic pole is attached to the ceiling, and the lower end of the rope is tied to the “step”. An adjustable board parallel to the axis of the machine serves as a support for the worker. Such machines even do very clean and delicate work; for grinding wood and for some other cases, alternating movement is even more expedient than continuous movement. The bow and alternating rotation are also used by watchmakers in their small lathes (see Watches), but now it is almost universally replaced by continuous rotation, through the “flywheel”. Although there is an indication that the flywheel (see) was used to set the machine in motion already in the 16th century, it began to come into general use only from the 18th century. The flywheel began to be placed under the machine; it was set in motion using a well-known mechanism consisting of a swinging step, a “hook” that served as a connecting rod, and a curved shaft (Table 4). The machine itself was first set up like the previous one, and an endless rope from the circumference of the flywheel was laid directly on the piece being processed. But soon they began to make a special “spindle” with two necks rotating in special “headstocks”, in holes filled with tin to reduce friction and abrasion. The free end of the spindle was equipped with a screw thread in order to screw various kinds of “chucks” onto it to secure the workpiece. Sometimes the left headstock was equipped with a fixed point, on the cylindrical rod of which a small pulley for the lace from the flywheel rotated freely. In this case, the object being processed was fixed “between the centers”, as in Fig. 3, and a special pin protruding from the side of the small pulley hooked onto the left end and imparted rotation to the work. This technique is called grinding on “dead centers”; it is also used in modern machines when the greatest possible precision of work is required. In fig. 4th shows an even more complex device, the so-called. "cartridge" screw cutting machine. The spindle necks are made significantly longer than the bearings that surround them, so that when rotating it can also move along its axis. Several short screws of different speeds are cut at the left end of the spindle, and hard wood planks with corresponding nut threads are fixed in the headstock. When these boards are lowered into the corresponding slots of the headstock, and the outermost one, not equipped with cuts, is raised and inserted into the corresponding annular cut of the spindle, it has no longitudinal movement and serves as an ordinary point. When this board is replaced by another, the spindle can make several turns along the helical line, and with the help of a stationary “comb” on the object being processed, a screw, external or internal, can be turned accordingly. At the beginning of the 19th century, when steam engines began to be built in large numbers, they began to demand accurate and fast work from the machine; the types described above had to be replaced with more advanced and durable ones. In this regard, the first figures were the English mechanic Maudsley (Maudsley, -) and the German mechanic Reichenbach (-). Reichenbach, while designing astronomical and geodetic instruments, dealt with small objects and therefore only improved the design of the wooden T. machine type Fig. 4, but the first one added to it a “support” for the cutting tool, allowing it to be moved with screws along the axis of the object being turned and in a direction perpendicular to it. Maudsley began to make T. cast-iron machines with a caliper; Clement, the inventor of the planing machine, improved the design of the spindle, began to introduce planed cast-iron frames for the machine and gave it a generally modern look, which, however, was developed only in the sixties of the 19th century, through the efforts of many people. Modern T. machines are made of cast iron: bed w(table drawing 5) is cast from one piece and screwed to the legs s. The bed is carefully planed on its upper surface, representing two flat, parallel rulers or a flat ruler in front and a parallel, pointed one in the back, so that the left headstock can be moved parallel to itself and secured D with spindle x, manual caliper Am, handyman Bn and right grandmother Cu. In machines driven by the worker’s foot, a shaft with a crank is mounted under the frame h, usually rotating between two pointed screws fixed in the legs S; a stepped flywheel is mounted on this shaft l transmitted through a belt I pulley movement l 1, put on the spindle X. Step t through a hook u, serving as a connecting rod, takes the swinging movement of the turner’s leg and turns it in a known manner into a circular one. The spindle makes up the main part of the machine; it is made of good steel, and the journals are hardened and then carefully ground. The machine shown (f. 5) has a medium-sized spindle with two cones rotating in hardened steel rings inserted into a cast-iron headstock. Both cones have apexes to the left, but different angles of inclination; A cylindrical tube is put on the spindle from the left end and held in place with a nut. When the spindle is single-tapered, it is made thicker than a screw threaded at the end X, so that the spindle can be inserted from the left when in the part k thrust screw D unscrewed enough. To operate, this screw must be carefully tightened so that its flat, hardened and polished end is in precise contact with the slightly convex and also hardened end of the double-cone spindle or fits neatly into the conical recess at the left end of the single-cone spindle (Fig. 5). The rings are drilled from the top for lubrication. The upper part of the right headstock is drilled along the geometric axis of rotation of the spindle, so that it moves without rotating using a screw at and nuts with handwheel z cylinder with insert "center" at. The rest for supporting hand tools consists of a T-shaped insert B, which can be lifted and rotated about a vertical axis, and its stand i equipped with a horizontal slot that allows it to be pulled forward and secured by turning the nut n. Caliper device A It can be better seen in the following drawings (tables 8 and 9), representing its vertical sections along the axis of rotation of the spindle and perpendicular to it. Foundation A, moving along the T. machine bed, represents a strong frame, planed in the shape of a prism, which is covered by the lower “carriage” IN equipped with a movable wedge v, carefully installed with screws so that it moves with the screw b and a nut m no lateral wobble. On the upper surface of this carriage, a longitudinal frame - a prism - rotates CD near the thorn With and secured at a designated angle with screws Χ . It is covered by the upper carriage E driven by a screw l and a nut n; On its upper surface, cutter 1, 2 is secured with a bolt YY nuts it up ABOUT, triangle gg and support screw R. When it is necessary to process only the side surface of long objects, they are equipped with small funnel-shaped recesses at the ends and placed between the “centers” of the machine. To make this object rotate with the spindle, put a “collar” on the left end (Table 13), press it with a screw and extend the hook of the chuck screwed onto the spindle as much as necessary so that it captures the tail of the clamp. If you also need to process one of the ends, drill a hole in it or cut a screw or nut, then this object is screwed with the other end into a screw cartridge (Table, Fig. 6). This similarity is cylindrical. glass equipped with two rows of crosswise screws d And d 1 ; By systematically tightening these screws, it is not difficult to “center” the object. This chuck is used primarily for turning objects from thick brass wire and from cylindrical steel and iron rods. For wood, chucks of the same type are made without screws, but of different diameters, made of metal or hard wood; The piece of wood being processed is simply hammered with its rounded end into such a chuck. The self-centering American cartridge is more convenient, but holds less firmly (table, Fig. 7). It is equipped with three dies 1, 2, 3, moving in the radial slots of the cartridge cover E, screwed with a ring Om ; On the very flat surface of this cartridge, an Archimedean spiral is cut, capturing the teeth on the underside of the dies. According to the property of this line, the internal ribs of the dies, fitted in one position, will remain on the same circle concentric with the axis of rotation and in all other positions to which they can be brought by rotating the cover relative to the cartridge with a spiral. In addition to those described, a large number of different cartridges were designed for different purposes. A modern machine tool is also very convenient for drilling: when an object is fixed in a chuck, you can drill it along the axis of rotation: having previously marked the center, that is, having carved a recess in this place by hand, insert the tip of the drill into it, rotate the spindle and press drill with the right headstock screw, while delaying the rotation of the drill itself. Or they insert the drill into the corresponding chuck, and press the object with the right headstock screw, putting a special chuck on the right tip in the form of a circle normal to the axis of rotation. The machine is also used for cutting screws. For optical glass frames and in general for connecting parts made from tubes, bone products and hard wood, it is necessary to cut short screws and nuts of different diameters and different stroke lengths. The left headstock of such a cartridge machine is shown in the table, Fig. 10. Its spindle has two cylindrical necks, at the rear, left end there is a cylindrical appendage on which cylindrical cartridges with different threads are put on and secured with a nut. The corresponding nut threads are made on a bronze star-shaped part that turns on the bottom of the slide, sliding up and down the back of the headstock by means of an eccentric with a lever. When it is necessary to cut a screw, the corresponding cutting of the star is moved towards the chuck; when it is necessary to simply sharpen, the star is lowered, and the end of the spindle is supported on the screw in a special fork, shown in Fig. 10 in a raised position. On the outer spindle screw there is a chuck with a pin, which is used to grip the clamp when sharpening “on the centers”; On the side, behind the pulley, a strip is visible, which serves to use the circular divisions marked on its front surface. These divisions are marked by small holes into which a point, attached to the side of the indicated strip, enters; they serve to mark the circumference of the object being processed (with the belt removed, of course). For the manufacture of long and thick screws, especially with a rectangular thread, “screw-cutting” T are used. machines with a master screw, which also serve as a “self-sharpening machine” for turning cylinders, planes and cones. Such a machine is shown in the table in Fig. 11. It consists of the same parts, but of a slightly different design; its frame is equipped with a so-called cutout. "gap" so that you can grind wheels of a radius greater than the height of its centers. Along its front side there is a long “mother screw”, engaged with the spindle by a system of variable gears, the supply of which is shown under the machine (on the left is a “universal” chuck with four adjustable screws, and on the right is a pulley for transmitting movement to the spindle from the drive). By means of a detachable nut, this screw can move the lower carriage of the support along the frame itself; another, transverse, screw slides along this carriage, the screw of which can also rotate from the spindle: in this case, its nut is separated and communicated with a snail sitting on the axis of the gear that transmits the rotation to the transverse screw of the carriage through another one visible in the figure. In order not to wear out the screw unnecessarily, for installations the carriage is moved through the gear strip, gear and handle visible in the figure. A manual support is mounted on the transverse carriage for convenient installation of the cutter. To the right of the carriage you can see the “lunette”: a fixed stand into which pieces of wood with a cutout are placed to support long objects so that they do not bend when turning. The left headstock is “overkill”: when the spindle should be rotated faster, the belt is put over the pulley, and the pulley is fastened to the spindle. When slow rotation is necessary, the pulley is disengaged from the spindle and a gear mounted on a special axis rotating in bearings prepared on the back side of the headstock is moved to the gear at its left end. The gear at the right end of this axis engages with the wheel at the right end of the spindle and causes it to rotate several times slower. To cut a screw of a given stroke, you need to know the stroke of the uterine screw. Let's assume that it is equal to 1 cm. If the screw rotates at the same speed as the spindle, its copy will begin to be cut; to get the screw in n times less stroke, you need to put on wheels so that it turns one revolution at n spindle revolutions. It is not difficult to calculate how many teeth you need to use for this purpose, but in practice you need to use the existing set of wheels; Since this set is limited, sometimes you have to be content with an approximation. Usually the machine comes with a table of possible and common combinations. If the diameters of the wheels on the spindle and on the screw are insufficient for direct engagement, an auxiliary wheel is introduced that engages with both of them and therefore does not change the transmitted speed ratio. Having introduced another second such wheel, we will change the direction of rotation of the screw and instead of the right screw we will begin to cut the left one, or vice versa. When you just need to sharpen the cylinder by self-grinding, choose wheels like for a low-speed screw. Sometimes, to simplify the design, in such non-screw-cutting self-sharpening machines, instead of a mother screw, a gear strip with a gear is installed, which receives movement from the spindle.
TURNING.
Soft wood requires fast rotation, about 10 revolutions per second for thin objects; The tools used are mainly semicircular and flat chisels (“rera” and “menzel”). Both differ from carpentry ones in their greater length, the absence of a “nut” on the tail inserted into the handle, and in the fact that the semicircular one is not sharpened straight, like a carpentry one, but its corners are ground off more than the middle; flat is sharpened on both sides so that the blade is inclined to length and one angle is sharp and the other is obtuse. When working, the tool is supported on a “rest” and applied to the surface being processed so that the lower chamfer of the blade is almost tangent to it. If you slightly raise the handle so that an angle of several degrees is formed between this chamfer and the tangent, the chips first become thicker, and then the tool begins to scrape: instead of chips, crumbs are obtained, and the surface remains unsmooth. To obtain a smooth surface, you always have to cut “along the layers” of wood, and not against them, as when planing with a knife; after turning, they sand it with sandpaper (see Emery) and then wipe it firmly with shavings of the same wood, which results in a slight shine on the surface. The cutting angle for soft wood is between 20 and 30°; for hard grades it can be 45°, and the tools can be deliberately forced to scrape rather than cut: the work is quieter, but it is easier to make complex shapes and patterns. To point brass, iron, and bone, a few simple tools are used by hand: a “stihel” consists of a steel rod of square cross-section, sharpened by one diagonal plane, resulting in one sharp trihedral angle and two cutting blades. If you place the gravel on the tool rest so that the short diagonal of its chamfer is almost vertical, and force its tip to cut slightly below the center line, then it acts very strongly, especially on iron and steel, but leaves a ribbed surface that can be smoothed with its blade. For brass, a straight tool with a rounded or two-chamfered end is more convenient. The cutting angle for iron is about 60°, and for brass it is blunter, from 70° to 80° and even up to 90° for final smoothing. The rotation speed for brass can be only slightly less than for wood, but for iron it should be 3 or 4 times less, otherwise the tool becomes dull and the work goes poorly. For heavy metal work, when there were no machines with supports yet, “hooks” were used: the cutting end of the tool was bent at a right angle, the long handle could be rested on the shoulders, and the “heel” on the tool rest. In this way, all the resistance was transferred to the tool rest, and it became easy for the worker to hold and guide the tool. The lathe hook was a special tool of the English "milwrights" (q.v.) of the first half of the 19th century; it has now fallen out of use. The shape of the tools for working metal using a caliper is carefully designed. First of all, we note that any self-sharpening tool will leave a helical groove on the side surface of the object being turned, and a groove in the shape of an Archimedean spiral on the plane normal to the axis of rotation. If the tip is round or triangular, then the groove will be relatively deep, but the protruding parts of each whorl will be cut off when the next one is formed, when the stroke of the helix is significantly less than the width of the chips being removed. The grooves will appear even more delayed if the tip is sharpened in such a way that it consists of two almost mutually perpendicular blades, of which one is almost tangent to the surface being formed, and the other, almost normal, goes forward and does most of the work. Such “side cutters” are necessary for turning necks and protrusions with recessed angles. But with this shape, the acute angle of intersection of both blades is easily blunted on steel and iron, so for turning smooth surfaces, they prefer a cutter with one straight blade, inclined 30 degrees to the axis of rotation, which is forced to cut not at an angle, but in the middle. Moving only along the radius of the object being ground, such a cutter would form a ruled hyperboloid of revolution (see), tangent to the cylinder in its neck, which is why, with longitudinal movement, such a cutter leaves a very smooth surface. Brass and cast iron are sharpened dry, but iron and steel give a smooth surface only when they are moistened with oil, a mixture of vegetable oil and turpentine, or a solution of soap mixed with oil. When removing the outer crust of castings containing scale and grains of sand, a simple cutter with a rounded end is preferred. For large T. machines, they find it advantageous not to forge the entire cutter from steel, but to use small pieces of steel rods, rolled to different cross-section profiles according to the needs, hardened and inserted into special “holders”, which in turn are screwed into the support. In this case, not only is there a saving in material, but the exact shape of the blade is maintained, because the cutting blocks are sharpened only on their transverse surface. Usually the surface is also treated with a grinding file while rotating on the machine, although the correctness of the shape is violated; if the surface is not subject to abrasion, then it can be sanded and polished using ordinary techniques. The success of the work depends on the correct installation of the tool. It is advisable to force the cutting tip to work in a horizontal plane passing through the axis of rotation, otherwise the "slope angle" DAQ(Fig. I above) will change as the object is ground, and if its surface is processed, perpendicular to the axis, then near the center the blade will stop working and will pass either below or above it.
This position is at the same time the most advantageous for working conditions: the resistance of thin chips is directed tangentially and can be expressed by force AQ, and the reaction of the tip is by force AR, exactly the opposite of the first. These forces, with uniform movement, cancel each other out, without causing components that tend to push the object being processed onto the cutter or move it away. If the cutter touches above the central plane (form I of the middle line), a resultant will appear AB, seeking to distance it from the object being processed; if it works lower, then this force will be directed in the opposite direction, the cutter will have a tendency to “stick”, cut deeper, if the chips become thicker either because an unevenness is encountered, or due to careless movement of the caliper screw. To combine both advantages, the upper surface of the cutter AB They usually make it oblique (Fig. I lower line) and install it on the line of centers. When removing thick chips, more work is required to bend them than to separate the metal particles, in which case the direction of the force Q will be approaching AE, a line dividing the cutting angle in half BAD, as for a wedge. This circumstance makes it necessary to raise the tip of the cutter or make its surface inclined, as far as possible, if necessary, give an angle of inclination DAQ from 3° to 4°, and the cutting angle BAD from 51° to 60° for iron, from 51° to 70° for cast iron and from 66° to 80° for bronze and brass. Experience has shown that the largest number of chips is obtained with the least amount of engine work at circumferential speeds in cm per second: 5.5 for iron, 4.0 for cast iron and 6.5 for bronze. The chips were 0.3 mm thick and varied in width from 10 to 40 mm. But in reality, driving force costs much less than the craftsman's time, so it is profitable to speed up the work by using more force and removing thicker chips at a higher speed. Therefore, in practice they deviate greatly from these speeds. According to Dejonc, these speeds are:
It is impossible to take even higher speeds because the cutter heats up, and the tool and the object being ground begin to tremble and the surface turns out to be uneven. Therefore, to speed up the operation of large T. machines, for example. when turning carriage wheels, “cutters” (or “milling cutters”, see) were recently successfully used instead of a cutter (Roth’s machine in Florisdorf, near Vienna). These are rotating cutting wheels with many points; the work is therefore distributed over a large surface and, with the expenditure of sufficient labor, proceeds many times faster. Another means for speeding up the work of heavy machine tools was invented in America: these are cutters made of a special type of steel that does not lose its hardness even when heated to a dark red heat; therefore, steel can be turned for “sharpening” at a speed on a circle of 10 cm, soft cast iron at 96 cm, gray cast iron at 50 cm, and brass at 100 cm per second. It is likely that this is one of the varieties of so-called naturally hard steel: these varieties usually contain, in addition to carbon, tungsten, titanium, molybdenum and other elements. Being heated above the temperature determined for each variety, they become solid upon cooling, even if this cooling occurs slowly. If they are heated a second time to another certain, but less high temperature, then upon cooling they turn out to be much softer. Heating that does not reach this second “critical temperature” remains without a significant effect on the hardness. The use of such cutters requires machine tools of a more durable design, since not all existing ones will allow the removal of thick chips at high speed without harmful vibrations. A very important role in modern mass fabrication of metal products is played by the so-called. "revolving T. machines". In the manufacture of weapons, sewing machines, bicycles, ladies' watches, electrical accessories, etc., tens of thousands of identical screws and other small turned parts are required, which must be so close to being identical that they can replace one another without any adjustment. To make such items from wire up to 3 cm in diameter, mostly brass, the spindle of the machine (table, Fig. 12) is drilled through to allow long wires to pass through and reduce the number of scraps (the support screw shown in the figure is inserted only when processing short, cast or forged objects, fixed in the chuck shown under the machine, into which lips can also be inserted in the form of boxes for pouring soft metal into irregularly shaped objects). Having removed as much wire as needed from the chuck, set the spindle in motion and move the first tool of the turret support toward it until a special stop screw is reached. Then the caliper is moved back, while a special pawl turns the upper part of the caliper, like the drum of a revolver, by a sixth of a revolution, so that in place of the first tool there is a second, etc. To cut a screw or to cut off the finished work, use a lever rotating in the headstock spindle. At its left end a part of the nut is fixed: when it is brought into contact with a screw chuck placed on the left end of the spindle, the point at the right end of the lever cuts the screw, and the support screw, sliding along the platform, limits the depth of cutting. The design of machine tools is extremely varied; often such a machine is adapted only for one specific job, while others operate completely automatically. The “copying machine,” used primarily for the manufacture of wooden gun stocks, shoe lasts, and other round objects, should also be included in the list of machine tools. Item being processed WITH(table fig. 4 can be rotated about a horizontal axis parallel to the axis of the model A, with which the axis of an object is linked by gears, so that it rotates at the same speed and in the same direction. Processing with cutters IN rotates about an axis parallel to the first two, but mounted on a slide sliding perpendicular to them. When the model and object are slowly rotated, the cutters cut it off until the thrust screw connected to the slide rests on the surface of the model and delays further movement. Then the same process begins in another section of the model. The principle of a copying machine is used in a wide variety of forms.
Literature is abundant, but books containing applicable information are few. Main book: Holtzapffel, "Turning and mechanical manipulation" (vol. IV,). The first volume was published in the city, but there is a new continued edition, published in the nineties. Thieme, "Fundamentals of Mechanical Engineering" (); Naidenko, “Manual for turners” (Ekaterinoslav,; much is suitable for students; the author does not go into explanations); of the same nature, but contains a lot of valuable information: E. Dejonc, “La Mechanique pratique” (P.,); Joshua Rose, "The practical Machinist".
William Macy found success in his first film, after which his life changed. An award-winning actor, he has established himself as one of the leading character actors. One day, while filming in Minnesota, Macy became interested in turning. He took lessons from a local turner and even bought his own machine to practice between filming.
At first glance, this beetle-eaten pine block did not seem like anything special, but after removing the bark, an excellent blank was discovered for turning a bowl with thin walls.
What prompted him to take up turning? “I’m like a chimpanzee: I was just intrigued by the work of a wood turner, and I immediately wanted to try to make something myself,” Macy says with a smile. Then he adds in a more serious tone: “I have always liked various containers: they are practical, I like to give them as gifts, knowing that they will not gather dust without use. People usually admire the shape of the vessels and enjoy contact with them - touching them, stroking them and smiling at the same time.” Having learned about William's passion for turning, we decided to visit his workshop in the suburbs of Los Angeles, taking with us the famous master Phil Brennion, who agreed to give the film actor some lessons. Under his guidance, by the end of the day, Macy was able to carve his first thin-walled, translucent bowl.
First steps: choosing the right material and tools
To turn a translucent vessel, a special material is needed. The wood should be light, fairly dense and have a beautiful pattern with characteristic marks, which gives it additional attractiveness. When Brennion pulled out a nondescript pine log about 20 cm in diameter, covered with frozen drops of resin and riddled with insect holes, from a plastic bag, we were surprised. But the workpiece turned out to be ugly only on the outside.
This piece was cut from a tree that had died from an attack by bark beetles. Their larvae feed on the cambium (the layer of living cells located under the bark), draining the tree to the point of death. When the larvae turn into beetles and emerge, fungi begin to grow in their passages, which cause the appearance of radial colored stripes in the thickness of the trunk.
Even if you can't find a unique blank like this, you can still carve a bowl that allows light to pass through the sides. Choose a light-colored wood, such as maple, and make sure it is raw rather than seasoned to make it easier to work with.
Note. This blank turned out to be longer than required to make the bowl. After completing the main task, the remainder of the block was used in experiments on turning a hollow vessel. To make such a bowl, a piece 150 mm long is enough.
With the rotation speed set at about 500 rpm and the tool rest 50 mm below the turning axis, Macy turned the workpiece with a grooved cutter.
The work requires only two turning tools: a 10 mm wide groove cutter and a 5 mm wide cutting cutter. For such delicate work they must be well sharpened. It will take a lot of time to carve a thin-walled bowl. (William Macy spent about six hours mastering this technique.) Brennion advises not to interrupt the process until the work is completed. Why? Wet wood, especially in thin pieces, dries very quickly and can crack or warp if left unattended. “If you have to take a break,” he says, “take fresh shavings, put them in a plastic bag and slide the bag over the unfinished bowl. Squeeze out the excess air and wrap it with tape. This will help equalize the moisture content of the workpiece and prevent cracks from occurring.”
Scene one: preparing the material
Macy shows the result of straightening the ends using a cutoff cutter. The workpiece can be attached to the faceplate. The central protrusion, if necessary, can be easily cut off with a chisel.
After removing the bark and cleaning the surface with a wire brush, Macy clamped the workpiece into the centers of the lathe and turned it by hand a few times to make sure it was secure and balanced. Then I roughed it down to a cylinder using a grooved cutter (Fig. 1 And photo A). The small width of the tool reduces the risk of it burying itself in the workpiece at the initial point. If the shape of the workpiece is close to cylindrical, you can use a wide rake to speed up the work. Using a groove cutter and parting cutter, he aligned the ends of the workpiece, cutting the wood almost flush to both centers (photo B).
Brennion and Macy then removed the workpiece from the machine and used screws to attach a faceplate to one of the ends, aligning it with the axis of the workpiece. The short protrusion at the end of the workpiece fit into the central recess of the faceplate. The attachment of the workpiece to the faceplate should be very secure. Macy installed the faceplate on the machine spindle, and used the rear center to support the opposite end of the workpiece. After that, I ground the workpiece again so that it rotates without beating.
Scene two: the beginning of turning the bowl
To make thin walls shine through from the inside, Brennion advises increasing the illuminated surface area by giving the bowl the shape of a wide cone with a narrow base.
Periodically turning off the machine to inspect the workpiece sandwiched in the centers, Macy begins to shape the bowl from the outside. The tool rest is installed perpendicular to the direction of movement of the cutter.
To turn this shape, the rotation speed was increased to 1000 rpm, and then a cone was formed using a grooved cutter (Fig. 2 And photo C). For now, you don’t have to worry about the accuracy of the external profile. But you need to leave more material at the bottom of the workpiece (about 75 mm in diameter) so that it can withstand the lateral pressure during turning. Brennion advises not to reduce this size until the end of the work. The finished bowl has a base with a diameter of about 50 mm.
Scene three: cavity formation
Before turning the internal contour, Macy moved the tailstock back and checked that the workpiece was securely fastened to the faceplate. Having placed the tool rest parallel to the end of the workpiece, he used a grooved cutter to select a recess in the center (Fig. 3). You can use a drill by inserting the drill chuck into the tailstock quill. Brennion advises drilling to the full depth at once while the workpiece has sufficient strength. Face turning of thin walls, according to Brennion, requires a special approach. When turning longitudinal fibers, the cutter is usually moved from the edge to the center. However, here the inside of the bowl needs to be sharpened from the center to the edges (photoD). This allows for better control of the process and reduces the risk of accidental damage to the thin walls of the bowl due to careless movement of the cutter.
Macy moves the tool rest parallel to the surface being processed, installing it at the height of the turning axis when working with the cutter from the outside and 25 mm lower when turning the internal volume.
“The thinner the walls become, the more careful you need to work,” warns Brennion. Thin walls made of raw wood dry out quickly, often losing their round shape. Keeping the tool sharp and carefully removing thin layers of material helps avoid trouble. Having roughed out the inner volume, Macy again began to work on the outer contour of the bowl (photo E). Having finished turning from the outside, he brought the walls to their final thickness, working with a cutter from the inside. Brennion explains that this processing sequence minimizes warping of thin walls.
For the walls to be translucent, Brennion explains, they must have a uniform thickness of no more than 4 mm. Any increase or decrease in thickness causes internal stresses that can tear the wood.
To control the wall thickness, turners used two methods. They shined light from a small lamp into the bowl and examined the back, checking for dark or light areas.
They also touched the walls of the rotating bowl with their fingers. Determination of thickness
Scene four: grinding, finishing and final movements with the cutter
A final sanding removes all cutter marks and prepares the bowl for finishing.
Having completed the contours from the base to the rim of the bowl, Macy began sanding using 120 to 220 grit sandpaper. (Fig. 4 And photoF). In such cases, sanding is often done by hand, but Macy uses a power drill to speed up the process.
To make the walls of the bowl transmit light better, he generously coated them with so-called Danish oil. (photoG). The composition is well absorbed into the wood and makes it more transparent. Film-forming coatings such as nitro varnish or polyurethane do not have this effect.
Although the workpiece was initially damp, the heat generated during turning and sanding dried the wood sufficiently to allow it to be treated with an oil compound. If you leave the bowl unfinished, it may warp or crack within minutes.
Oil soaking the finished bowl enhances it even further by enhancing the contrast between dark and light areas and adding an amber tint.
Macy finally separated the bowl from the rest of the blank using a cutter. After sanding and finishing the bottom, he got a good look at it in the California sun.
Our hero
Profession: film actor.
Specialization: performance of characteristic roles and turning of utilitarian vessels.
Workshop: superstructure measuring 7.3x7.3 m above the garage. The main role is played by the Powermatic 4224 lathe, secondary roles are played by other machines, mainly engaged in the primary processing of turning workpieces.
Experience: His father was a carpenter who built the family home, so William was familiar with tools from childhood. He became interested in turning by chance, but after trying it once, he was hooked.
Most often used: lathe, turning tools and electric sharpener.
Favorite wood species: American hornbeam, which is durable and looks great in turned pieces, and walnut, which has a beautiful color.
Favorite finish: Behlen wood cookware oil is easy to apply and restore.
Top tip:“Learn to sharpen your cutters and understand how they and the lathe work. And always be careful - safety comes first. My working methods allowed me to keep all my fingers intact, earning only a couple of scars.”
Turner has been and remains one of the most in demand. Wood and metal processing is the area of application of turning craft. To optimize labor, accuracy and speed of manufacturing parts, there are many machines and other equipment that are constantly being improved, allowing the master to perform the most complex and precise operations.
Specifics of the term
Turning has come a long way of development before it acquired the forms of production that we know now. At the present stage, this includes cutting metal and non-metallic materials and alloys, applying threads of various types to parts, turning individual elements of equipment and applying various notches, grooves, etc. to them, turning wooden blanks to give them the desired shape. The final products of production are the familiar bolts and nuts, valves and adapters, plugs and many other fittings, as well as various housings and other parts.
Turning is closely related to turning production. This concept fits, in principle, any enterprise where appropriate machines and other tools are installed for working with different materials, from single orders to an entire series or line. In order to be able to perform the necessary actions and understand each stage of the operation, you need to have a good knowledge of the properties of heat treatments of materials, navigate the drawings and have many other knowledge. Therefore, turning is considered a complex science, interacting most closely with related ones.
History and traditions
If we go back to the distant past, we can remember that our ancestors used dishes that were hollowed out, carved and turned from wood, as well as household items, furniture and even toys. This was done first in a crude way and with improvised means, and then on devices that resembled lathes and became their prototypes. This is how the turned brothers, bowls, and cups appeared. Consequently, it is from there that modern turning takes its origins. To this day, turned parts and entire products are widely used in folk crafts. For example, various kitchen accessories: stands for hot kettles, pots and pans, etc.; interior design accessories: wooden “curtains” made of polished round pieces of wood or sticks, souvenir sculptures and figurines. Lathes process almost any type of wood quickly and accurately, with all the necessary precision. In this case, the size of the product does not play a special role. You can sharpen both a miniature netsuke, indicating even the smallest details, and a large product. Such objects give special beauty and expressiveness
there is artistic painting.
With the development of industry and the active use of iron in production, metal turning, technically close to woodworking, arose. Nowadays, not a single production process can do without it. The most complex mechanisms are basically made from parts created on lathes. Therefore, a turner, especially a milling machine operator, is always in demand at enterprises. And training in turning is carried out in all specialized vocational schools and in many large plants and factories.
Summary
The profession of a turner, interesting and difficult, requires great self-discipline, accuracy and constant self-improvement. This is one of those specialties that support the most complex high-tech processes.
The book discusses the technology of processing parts on lathes; provides information about equipment, tools, devices and the selection of the most rational cutting modes; issues of mechanization and automation of parts processing on lathes, as well as safety issues when working on these machines are covered; examples of the work of innovative turners are given.
The book is intended as a textbook for training turners in urban vocational schools and can be used in the network of individual and team training at industrial enterprises.
BASIC CONCEPTS ABOUT THE DEVICE OF A LATHE - SCREW-CUTTING MACHINE. PURPOSE OF LATHE MACHINES.
The most common method of processing materials by cutting is processing on lathes. Lathes process parts that primarily have the shape of rotating bodies (rollers, mandrels, bushings, blanks for gear wheels, etc.). In the manufacture of such parts, it is necessary to process cylindrical, conical, shaped surfaces, cut threads, grind grooves, process end surfaces, drill, countersink and ream holes, etc. When performing these works, the turner has to use a wide variety of cutting tools: cutters, drills, countersinks, reamers, taps, dies, etc.
TYPES OF LATHES. Lathes constitute the largest group of metal-cutting machines in machine-building plants and are very diverse in size and type. The main dimensions of lathes are: the largest permissible diameter of the workpiece being processed above the bed, or the height of the centers above the bed; distance between centers, i.e. a distance equal to the longest length of the part that can be installed on a given machine.
All lathes according to the height of the centers above the bed can be divided into:
small machines - with center heights up to 150 mm; medium machines - with a center height of 150-300 mm; large machines - with a center height of more than 300 mm. The distance between centers for small machines is no more than 750 mm, for medium ones 750, 1000 and 1500 mm, for large ones from 1500 mm.
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The following textbooks and books.
ABOUTlearning turning - this is a section of the site that contains information not only for professional turners, but also for turning students. Turning is very promising, because in our time, try to find a real turner.
Pprofession of turnerhighly paid, so if you are not lazy and want to earn good money for your work, start learning the basics of turning on our website.
The lathe is designed for processing by cutting a body by rotation, including rotating end planes and helical surfaces. In addition, work not related to cutting can be performed on lathes.
List of all lathe capabilities very big and consideration lathe functions will take a lot of time. AND Learn all the functions of a lathe in one lesson it’s practically impossible, but gradually we will get to know everyone intricacies of turning. Turning training we will start using the following list lessons on turning.
Turning lessons :
Lesson #1. Lathe device
Lesson #2. Working on a lathe or operating a lathe
Content:
1. Tocar cutters
Tocar cutters- These are special cutting tools that are used for turning parts.
TOkar cutters are used as the main tool for turning, planing, and other work on machine tools.
DFor high-quality and precise processing of the part and achieving the required shapes and sizes of the product, a turning cutter is used, with which layers of material are sequentially cut off.
INIn the process of cutting a layer of material, the cutter cuts into it, removing chips from its surface.
ABOUTThe sharp edge of the cutter is its main working element.
WITHOver time, the cutter is subject to wear, as evidenced by chipping of the cutting part (edge). To use a turning cutter in the future, it must be re-sharpened.
1.1 The device of a turning cutter
1.2 Feed of turning tool
1.3 Cutting metal with a turning tool
1.4 Cutting surface
1.5 Cutter design
1.6 Turning tool angles
1.7 Wear and durability of cutter
1.8 Cutters for lathes
1.9 Materials for turning tools
1.10 Designs of turning tools
1.11 Manufacturing of carbide cutters
1.12 Manufacturing of cutters with blades
1.13 Manufacturing of high-speed and carbon cutters
2. Tokar machine
Tokar machine -This is a machine for processing parts by cutting and turning.
ABOUTThe main work performed on lathes: turning, boring and turning of various types of surfaces, threading, processing the ends of parts, drilling, countersinking and cutting holes.
Zthe workpiece is installed in the center and rotates using a spindle, then the feed mechanism moves the cutting tool, the cutter, together with the support of the running shaft.
DTo perform additional types of operations on the machine, such as grinding, drilling, milling holes, additional equipment is installed on the machines.
TThe window-screw-cutting machine is designed for lathe work with non-ferrous and ferrous metals.
TThe window-screw-cutting machine consists of:
- WITHtannin is the main part of the machine, which is the framework for mounting all the mechanisms of the machine.
- Pheadstock – it is also called the spindle headstock, due to the placement of the spindle, gearbox and other elements in it.
- TOThe feed box provides movement from the spindle to the support.
- WITHSupport – designed to secure the cutting tool and feed it.
- Fartuh - necessary to convert the rotation of the roller into the movement of the caliper.
- Ccenter - an installation for supporting a workpiece or tool.
2.1 Screw-cutting lathe model 1A62
2.2 Friction clutch of lathe model IA62
2.3 Tailstock design
2.4 Design of a screw-cutting lathe
2.5 Care of the lathe
2.6 Adjusting the lathe
2.7 Lathe safety
2.8 Devices for securing parts processed in centers
2.9 Lathe accuracy
Zhere you will find out how to determine and adjust the accuracy of a lathe, master concepts such as rigidity during turning, machining on mandrels, working with a mandrel.
Pravila work With spindle mandrels. In the turning section we consider screw cutting lathes, such as screw-cutting lathe 1A62. More details about turning tools, their types, turning tool materials their design. Wear and durability of the cutter also have a significant impact on turning.