Goal of the work
1. Introduction to processing methods conical surfaces on lathes.
2. Analysis of the advantages and disadvantages of methods.
3. Choosing a method for manufacturing a conical surface.
Materials and equipment
1. Screw-cutting lathe TV-01 model.
2. Required kit wrenches, cutting tool, protractors, calipers, blanks of manufactured parts.
Work order
1. Read carefully the basic information on the topic of work and understand the general information about conical surfaces, methods of processing them, taking into account the main advantages and disadvantages.
2. With the help of the training wizard, familiarize yourself with all the methods of processing conical surfaces on a screw-cutting lathe.
3. Complete the teacher’s individual assignment on choosing a method for manufacturing conical surfaces.
1. Title and purpose of the work.
2. Scheme straight cone indicating the main elements.
3. Description of the main methods of processing conical surfaces with diagrams.
4. Individual task with calculations and justification for the choice of one or another processing method.
Basic provisions
In technology, parts with external and internal conical surfaces are often used, for example, bevel gears, rollers of tapered bearings. Tools for making holes (drills, countersinks, reamers) have shanks with standard Morse tapers; machine spindles have a tapered boring for the shanks of tools or mandrels, etc.
Machining parts with a conical surface is associated with the formation of a cone of rotation or a truncated cone of rotation.
Cone is the body formed by all the segments connecting some fixed point with the points of the circle at the base of the cone.
The fixed point is called the top of the cone.
A segment connecting a vertex and any point on a circle is called forming a cone.
Cone axis, is called the perpendicular connecting the vertex of the cone with the base, and the resulting straight segment is cone height.
The cone is considered direct or cone of rotation, if the axis of the cone passes through the center of the circle at its base.
A plane perpendicular to the axis of a straight cone cuts off a smaller cone from it. The remaining part is called truncated cone of revolution.
A truncated cone is characterized by the following elements (Fig. 1):
1. D And d – diameters of both the larger and smaller bases of the cone;
2. l – height of the cone, distance between the bases of the cone;
3. cone angle 2a – the angle between two generatrices lying in the same plane passing through the axis of the cone;
4. cone angle a – the angle between the axis and the generatrix of the cone;
5. slope U– slope angle tangent Y = tg a = (D –d)/(2l) , which is denoted decimal(for example: 0.05; 0.02);
6. taper – determined by the formula k = (D –d)/l , and is indicated using a division sign (for example, 1:20; 1:50, etc.).
The taper is numerically equal to twice the slope.
Before the dimensional number that determines the slope, the sign Р is applied , the acute angle of which is directed towards the slope. Before the number characterizing the taper, a sign is applied, the acute angle of which should be directed towards the top of the cone.
In mass production on automatic machines for turning conical surfaces, copy rulers are used for one constant angle of inclination of the cone, which can only change when the machine is readjusted with another copy ruler.
In single and small-scale production on CNC machines, turning of conical surfaces with any cone angle at the apex is carried out by selecting the ratio of longitudinal and transverse feed rates. On non-CNC machines, conical surfaces can be machined in four ways, listed below.
Treatment center holes. Inspection of conical surfaces
Center hole machining. In parts such as shafts, it is often necessary to make center holes, which are used for subsequent processing of the part and for restoring it during operation. Therefore, alignment is performed especially carefully. The center holes of the shaft must be on the same axis and have the same dimensions at both ends, regardless of the diameters of the end journals of the shaft. Failure to comply with these requirements reduces the processing accuracy and increases the wear of centers and center holes. The designs of the center holes are shown in Figure 40, their dimensions are in the table below. Most widespread have center holes with a cone angle of 60 degrees. Sometimes in heavy shafts this angle is increased to 75 or 90 degrees. To ensure that the top of the center does not rest against the workpiece, cylindrical recesses with a diameter d are made in the center holes. To protect against damage, reusable center holes are made with a safety chamfer at an angle of 120 degrees (Figure 40 b).
Rice. 40. Center holes
| Workpiece diameter | The smallest diameter of the shaft end journal Do, mm | Nominal center hole diameter d | D no more | l no less | a |
| Over 6 to 10 | 6,5 | 1,5 | 1,8 | 0,6 | |
| Over 10 to 18 | 2,0 | 2,4 | 0,8 | ||
| Over 18 to 30 | 2,5 | 0,8 | |||
| Over 30 to 50 | 7,5 | 3,6 | 1,0 | ||
| Over 50 to 80 | 4,8 | 1,2 | |||
| Over 80 to 120 | 12,5 | 1,5 |
Figure 41 shows how the rear center of the machine wears out when the center hole in the workpiece is made incorrectly. When there is misalignment (a) of the center holes and misalignment (b) of the centers, the part is skewed during processing, which causes significant errors in the shape of the outer surface of the part. Center holes in small workpieces are machined various methods. The workpiece is secured in a self-centering chuck, and a drill chuck with a centering tool is inserted into the tailstock quill.
Rice. 41. Wear of the rear center of the machine
Center holes with a diameter of 1.5-5 mm are processed with combined center drills without a safety chamfer (Figure 42d) and with a safety chamfer (Figure 41e on the right).
Center holes large sizes processed first with a cylindrical drill (Figure 41a on the right), and then with a single-tooth (Figure 41b) or multi-tooth (Figure 41c) countersink. Center holes are machined with the workpiece rotating; The centering tool is fed manually (from the tailstock flywheel). The end in which the center hole is processed is pre-cut with a cutter. Required size The center hole is determined by the recess of the centering tool, using the tailstock flywheel dial or the quill scale. To ensure the alignment of the center holes, the part is pre-marked and supported with a steady rest during alignment.
Rice. 41. Drills for creating center holes
The center holes are marked using a marking square (Figure 42a). Pins 1 and 2 are located at equal distances from the edge AA of the square. Having placed the square on the end and pressing the pins to the neck of the shaft, a mark is drawn along the edge AA at the end of the shaft, and then, turning the square 60-90 degrees, the next mark is drawn, etc. The intersection of several marks will determine the position of the center hole at the end of the shaft. For marking, you can also use the square shown in Figure 42b. After marking, the center hole is marked. If the shaft journal diameter does not exceed 40 mm, then the center hole can be punched without preliminary marking using the device shown in Figure 42c. The body 1 of the device is installed with the left hand at the end of the shaft 3 and the center of the hole is marked with a hammer blow on the center punch 2. If during operation the conical surfaces of the center holes are damaged or unevenly worn, then they can be corrected with a cutter; in this case, the upper carriage of the caliper is rotated through the cone angle.
Rice. 42. Marking center holes
Inspection of conical surfaces. The taper of the outer conical surfaces is measured using a template or universal goniometer. For more precise measurements Bushing gauges are used, Figure d) and e) on the left, with the help of which they check not only the angle of the cone, but also its diameters. 2-3 marks are applied to the treated surface of the cone with a pencil, then a bushing gauge is put on the measuring cone, lightly pressing on it and turning it along the axis. With a correctly made cone, all marks are erased, and the end of the conical part is located between marks A and B of the bushing gauge. When measuring conical holes a plug gauge is used. The correct machining of a conical hole is determined (as when measuring external cones) by the mutual fit of the surfaces of the part and the plug gauge. If the marks drawn with a pencil on the plug gauge are erased at a small diameter, then the cone angle in the part is large, and if large diameter- the angle is small.
>>Technology: Manufacturing of cylindrical and conical parts hand tools
Cylindrical parts, which in cross section have the shape of a circle of constant diameter, can be made from square bars. The bars are usually cut from boards (Fig. 22, a). The thickness and width of the bar should be 1...2 mm larger than the diameter of the future product, taking into account the allowance (margin) for processing.
Before making a round part from a bar, it is marked. To do this, at the ends of the workpiece, by intersecting the diagonals, find the center and use a compass to draw a circle around it with a radius equal to 0.5 of the workpiece diameter (Fig. 22, b). Tangent to the circle from each end, use a ruler to draw the sides of the octahedron and use a thicknesser to draw lines 1 of the adjacent edges, width B, along the sides of the workpiece.
The workpiece is fixed on the workbench lid between wedges or installed in special device(prism) (Fig. 22, d).
The edges of the octahedron are cut with a sherhebel or a plane to the marking lines of the circle (Fig. 22, c). Once again, tangents to the circle are drawn, lines 2 are drawn along the ruler and the edges of the hexagon are cut off (Fig. 22, d).
Further processing is carried out across the fibers, rounding the shape first with a rasp, and then with files with finer notches (Fig. 22, e).
The cylindrical surface is finally treated with sandpaper. In this case, one end of the workpiece is fixed in the clamp of the workbench, and the other is covered with sanding paper and rotated. Sometimes the workpiece is wrapped in sandpaper, clasped with the left hand, and rotated with the right hand and moved along its axis of rotation (Fig. 22, e). The workpiece is polished similarly from the other end.
The diameter of the part is measured with calipers first on the part (Fig. 23, a), and then checked with a ruler (Fig. 23, b). 
The sequence of all the listed operations when obtaining a cylindrical workpiece from a square bar can be written down in a route map. This map records the sequence (route, path) of processing one part. Table 2 shows a route map for making a shovel handle.
In Fig. Figure 24 shows a drawing of a shovel handle. 
Practical work
Manufacturing of the product cylindrical
1. Develop a drawing and make a route map for the manufacture of a cylindrical or conical product, for example, shown in Fig. eleven.
2. Mark and make a shovel handle according to (Fig. 24) and the route map (Table 2).
♦ Calipers, route map.
1. What is the sequence of manufacturing a cylindrical and conical part?
2. How to measure the diameter of a part with calipers?
3. What is written in the route flow chart?
Simonenko V.D., Samorodsky P.S., Tishchenko A.T., Technology 6th grade
Submitted by readers from the website
External and internal cones up to 15 mm long are processed with cutter 1, the main cutting edge of which is set at the required angle a to the cone axis, carrying out longitudinal or cross feed(Fig. 30, a). This method is used when the workpiece being processed is rigid, the cone slope angle is large, and high demands are not placed on the accuracy of the cone slope angle, surface roughness and straightness of the generatrix.
Rice. thirty.
Internal and external cones of short length (but longer than 15 mm) at any angle of inclination are processed with the upper slide turned (Fig. 30, b). The upper slide of the caliper 1 is installed at an angle in the center line of the machine, equal to the inclination angle of the cone being turned, along the divisions on the flange 2 of the rotating part of the caliper. The angle of rotation is determined by the marks marked on the transverse slide of the caliper.
Machining external cones with an offset tailstock is used for relatively long workpieces with a small slope angle (Fig. 30, c). In this case, the workpiece 2 is fixed only in the centers 1. Taking into account the inevitability of wear of the center surfaces even at small angles of inclination of the cone, processing is carried out with cutter 3 in two steps. First, the cone is rough-processed. Then the center holes are corrected. After this, finishing grinding is carried out. To reduce the development of center holes in such cases, centers with vertices in the form of a spherical surface are successfully used. Transverse displacement of the tailstock is usually allowed by no more than 1/5 of the length of the workpiece.
Grinding external and internal conical surfaces using a universal carbon ruler is used when processing workpieces of any length with a small cone angle, up to approximately 12° (Fig. 30, d). The tracing ruler 1 is installed on the plate 5 parallel to the generatrix of the conical surface to be turned, top part At the same time, caliper 4 rotates 90°. The angle of rotation of the ruler during adjustment is measured using the divisions (millimeter or angular) marked on plate 5. The plate is attached using brackets to the machine bed. After turning the ruler around the axis to the required angle a, it is secured with nut 6. In the groove of the ruler there is a slider 7, rigidly connected to the transverse slide 2 of the caliper. When turning, the cutter together with the support moves in longitudinal direction and under the action of the slider sliding in the slot of the ruler - in the transverse direction. In this case, a conical surface with an apex angle of 2a will be ground. The angle of rotation of the ruler must be equal to the angle of inclination of the cone. If the ruler scale has millimeter divisions, then the rotation of the ruler is determined by one of the following formulas:
where h is the number of millimeter divisions of the scale of the carbon ruler; H is the distance from the axis of rotation of the ruler to its end, on which the scale is applied; D is the largest diameter of the cone; d—smallest cone diameter; tga is the angle of inclination of the cone; K - taper
(K= (D-d)/l); l is the length of the cone.
When a>12°, the so-called combined processing method is used, in which the angle of inclination is divided into two angles: a1 = 11-12°; a2 =a - a1. The copy ruler is set at an angle a1 = 12°; A tailstock shifted to process a conical surface with an angle of inclination a2 = a - 12°.
The method of processing conical surfaces using a carbon ruler is quite universal and provides high accuracy, and setting up the ruler is convenient and quick.
Regardless of the method of processing the cone, the cutter is installed exactly at the height of the centers of the machine.
Machining of conical and shaped surfaces
Conical surface processing technology
General information about cones
A conical surface is characterized by the following parameters (Fig. 4.31): smaller d and larger D diameters and the distance l between the planes in which circles with diameters D and d are located. Angle a is called the angle of inclination of the cone, and angle 2α is called the angle of the cone.
The ratio K= (D - d)/l is called taper and is usually indicated with a division sign (for example, 1:20 or 1:50), and in some cases with a decimal fraction (for example, 0.05 or 0.02).
The ratio Y= (D - d)/(2l) = tanα is called the slope.
Methods for processing conical surfaces
When processing shafts, transitions between surfaces that have a conical shape are often encountered. If the length of the cone does not exceed 50 mm, then it can be processed by cutting wide incisor. The angle of inclination of the cutting edge of the cutter in plan must correspond to the angle of inclination of the cone on the machined part. The cutter is given a transverse feed movement.
To reduce the distortion of the generatrix of the conical surface and reduce the deviation of the angle of inclination of the cone, it is necessary to install the cutting edge of the cutter along the axis of rotation of the workpiece.
It should be taken into account that when processing a cone with a cutter with cutting edge with a length of more than 15 mm, vibrations may occur, the level of which is higher, the longer the length of the workpiece, the smaller its diameter, the smaller the angle of inclination of the cone, the closer the cone is to the middle of the part, the greater the overhang of the cutter and the less strength of its fastening. As a result of vibrations, marks appear on the treated surface and its quality deteriorates. When processing hard parts with a wide cutter, there may be no vibrations, but the cutter may shift under the influence of the radial component of the cutting force, which leads to a violation of the cutter’s adjustment to the required angle of inclination. (The offset of the cutter depends on the processing mode and the direction of feed movement.)
Conical surfaces with large slopes can be processed by turning the upper slide of the caliper with the tool holder (Fig. 4.32) at an angle α, equal to angle inclination of the processed cone. The cutter is fed manually (using the handle for moving the upper slide), which is a disadvantage of this method, since the unevenness of the manual feed leads to an increase in the roughness of the machined surface. Using this method, conical surfaces are processed, the length of which is commensurate with the stroke length of the upper slide.
A long conical surface with an angle α= 8... 10° can be machined when the tailstock is displaced (Fig. 4.33)
At small angles sinα ≈ tanα
h≈L(D-d)/(2l),
where L is the distance between centers; D - larger diameter; d - smaller diameter; l is the distance between the planes.
If L = l, then h = (D-d)/2.
The tailstock displacement is determined by the scale marked on the end of the base plate on the flywheel side and the mark on the end of the tailstock housing. The scale division is usually 1 mm. If there is no scale on the base plate, the tailstock displacement is measured using a ruler attached to the base plate.
To ensure the same taper of a batch of parts processed by this method, it is necessary that the dimensions of the workpieces and their center holes have minor deviations. Since misalignment of machine centers causes wear on the center holes of the workpieces, it is recommended to pre-machin the conical surfaces, then correct the center holes and then perform final finishing. To reduce the breakdown of the center holes and the wear of the centers, it is advisable to make the latter with rounded tops.
Quite common is the processing of conical surfaces using copying devices. A plate 7 (Fig. 4.34, a) with a tracing ruler 6 is attached to the machine bed, along which a slider 4 moves, connected to the support 1 of the machine by a rod 2 using a clamp 5. To freely move the support in the transverse direction, it is necessary to disconnect the screw for the transverse feed movement. When the caliper 1 moves longitudinally, the cutter receives two movements: longitudinal from the caliper and transverse from the tracing ruler 6. The transverse movement depends on the angle of rotation of the tracing ruler 6 relative to the axis of rotation 5. The angle of rotation of the ruler is determined by the divisions on plate 7, fixing the ruler with bolts 8. The movement of the cutter feed to the cutting depth is carried out by the handle for moving the upper slide of the caliper. External conical surfaces are processed with through cutters.
