Lathe driving chucks purpose, types, GOST, drawings

Leash devices

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Turning

Leash devices

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Drive devices are used to transmit rotation from the spindle to the workpiece installed at the centers. The simplest of them is a turning clamp. The bent shank of the clamp fits into the radial groove of the faceplate mounted on the machine spindle. Rotating together with the spindle, the faceplate carries with it the clamp, and with it the workpiece installed in the centers. Clamps with straight shanks are also used; to work with them, drive faceplates are used, in which a pin or bar serves as a lead. Working with a clamp poses a certain danger: there may be cases where the shank of the clamp catches a worker’s clothing. Therefore, for safety reasons, faceplates with protective covers are used (safety faceplates). To avoid damaging the surface of the workpiece being clamped, a split sleeve is put on it or rubber is placed under the clamping bolt.

To reduce the time for installing and removing the clamp, quick-release and self-clamping clamps are used. The main part of a self-clamping drive clamp is a ring that is put on a workpiece installed in the centers. When the spindle is turned on, the plang;aiba acts on the driver, which, turning on an axis, grips the workpiece with a corrugated working surface. When cutting, this clamp clamps the workpiece more reliably, the larger the cross-section of the chips.

1. CARBIDE CENTERS: a - with a deposited layer of hard alloy, b - with a soldered tip

2. ROTATING CENTER FOR LIGHT RADIAL LOADS (UP TO 200 KG): 1 - cover. 2 - radial bearing. 3 - torus bearing. 4 — body with shank. S - center. 6 - needle bearing

3. APPLICATION OF THE CLAMP (a), DESIGNATION DIAGRAM (b): 1 - faceplate, 2 - front center. 3 - clamp. 4 - rear center, 5 - quill

4. SAFE PLATES: a – with a driving pin, b – with a driving strip (plbnka) “3- leash (finger or

5. SELF-CLAMPING DRIVE CHUCK 1—rings, 2—axle. 3—spring. 4 - leash

6. SELF-CLAMPING DRIVE CHUCK: 1 - faceplate, 2 - “floating ring”, 3 - cam, 4 - cam axis

7. DRIVE MANDLE: 1 - mandrel body with a conical shank. 2 - drive washer with end teeth. 3 - floating center. 4—spring. 5 - spring adjusting screw

The transmission of torque from the spindle to the workpiece is often carried out with a special driving self-clamping chuck (faceplate) with eccentric cams. The design of such a chuck by the innovative turner V.K. Seminsky is shown in Fig. 36. The presence of a “floating ring” on which the axes of the cams are located makes it possible to secure workpieces with an uneven outer surface (for example, forgings).

In Fig. 7 shows a driving mandrel, which carries the workpiece with teeth located at the working end of the driving washer. The workpiece is pressed against the teeth by the center of the tailstock.

The driver for rollers of small diameters can be a corrugated driver. To process tubular workpieces, “brushes” are also used, which have teeth on the working surface - corrugations. Small diameter rollers (up to 20 mm) can be fixed in reverse centers. The end cones and chamfers are pre-machined on the workpiece, and the front and rear centers have corresponding holes with seat cones. The workpiece is driven into rotation due to friction between the front return center and the workpiece. The reverse center fastening method is used only for finishing. Installation of workpieces in the centers (with putting on a clamp) lasts 0.25-0.6 minutes (depending on the mass of the part). Installation in centers with a driving self-clamping chuck (faceplate) or mandrel, as well as installation in friction clamps, reduces the time for clamping and removing the part by almost half. Experienced turners process small-diameter rollers, securing them in reverse (with a chamfer base).

8. SECURING THE WORKPIECE WITH THE HELP OF A DRIVE (a), DESIGNATION DIAGRAM (b): 1.2 - centers

Rolled blanks are mounted in a three-jaw chuck with a center support installed in the tailstock quill.

Centers

Based on the size and shape of the workpieces, various types of centers are used when processing them (Fig. 1). The working angle forming the top of the center - a) is always 60°. The conical planes of the tail 2 and working 1 components of the center must be smooth, without nicks. Any roughness creates errors when processing parts.

Fig.1. Centers:

a – straight; b – with a reverse cone; c – with a cut cone; g – spherical; d – with a corrugated working surface; e – with a carbide working surface; 1 – working part; 2 — tail part; 3 – supporting part

The cross-section of the support 3 is always smaller than the small cross-section of the cone of the tail component 2. This feature allows you to dismantle the center by knocking it out of the socket without damaging the conical plane of the tail component. Figure b) shows the center that is used when processing parts with a cross section of up to 4 mm. Instead of centering holes, they have an outer cone with an apex angle of 60°.

It extends inside the center cone, which is why it is called inverse. If it is necessary to trim the end of a part, use the center cut from the back, position - c). It is located in the tailstock quill of the machine.

A center having a working component with a spherical surface - d) is used when processing a part that is not coaxial with the rotation of the machine spindle.

The center, which has a corrugated plane of the working component - d), is used for processing the driverless chuck of parts that have large center holes. At the time of operation, the front center rotates following the workpiece, representing only a support.

The rear center remains stationary and is therefore subject to heavy wear. This is a consequence of loss of hardness as a result of increased heating.

To prevent wear, the working component of the rear center is made of hard alloys - e). When processing workpieces at high cutting speeds, under high loads, rear rotation centers are used (Fig. 2).

Rice. 2. Rotating center:

1 – center; 2 – roller bearing; 3, 5 – ball bearings; 4 – body

An axis is installed in the tail component 4 of this center in the rolling bearings 2, 3, 5. At its end there is a working component 1. This gives it rotation along with the workpiece.

Serrated and pin driver chucks

To process shafts, when the use of machines is necessary, gear and pin drive chucks are used, transmitting rotation of the part through the end with the ability to process the side surface.

Set of serrated driver chucks

The part is processed at the front of the floating center, transmitting rotational motion with the possibility of deflection. This type of fasteners provides reliable fixation in the axial direction, allowing for high-quality processing.

Clamps

In Fig. Figure 3 shows that rotation from the spindle to the part, which is located in the centers of the machine, is transmitted through clamps. They are installed on the workpiece and secured with bolt 1 – a). Shank 2 of the clamp rests against the pin on the driving chuck. A self-tightening clamp is most convenient to use – b). Its shank 2 is installed movably in the body 5 on the axis 4.

Rice. 3 Turning clamps: a - simple: 1 - bolt; 2 — tail part; b - with self-tightening; 1 - thrust screw; 2 — tail part; 3 - spring plate; 4 - finger; 5 - prismatic body.

The bottom of the shank 2 on the workpiece side is made in the form of an eccentric to the axis 4 with notches. To place the clamp on the part, shank 2 is tilted towards spring 3. After placing the clamp, the spring pre-tensions the part with the shank. During the operation, the finger-lead of 1 cartridge completely tightens the part in proportion to the cutting power.

Workpiece processing scheme

Figure No. 1. Scheme of part processing. Designation of device elements: 1 - drive cartridge; 2 – fastening leash-clamp; 3 – fixing bolt; 4 – movable steady rest; 5 – product being processed.

Lathe driver chucks used in turning work are made in the form of a disk with four grooves and a threaded bushing having identical dimensions to the headstock spindle. When using a straight clamp, a movable pin is installed in the cartridge, fixed with a nut in the groove of the fastener. When processing the workpiece, the pin rests against the tail of the clamp. The cartridges used must comply with GOST 2571-71, GOST 13364-67, GOST 1435-99 and GOST 25557-2006 for all established parameters.

Download GOST 2571-71 “Drive-type lathe chucks”

If a curved clamp is used during a turning operation using a lathe, the pin is not used, since the tail of the clamp is installed in the groove of the locking element.

Drawing No. 2. Drive chuck design. Designation: the main elements that make up the fastening element of the workpiece being processed.

This design has protruding parts, which allows the possibility of injury to the specialist processing the product. To eliminate the possibility of injury, a closed cartridge is used, made in the form of a casing with a boss and a threaded sleeve identical to the open element. The clamp is hidden inside the casing, which ensures safe work.

Drawing No. 3. The design of the driving chuck, made with a closed body. Designation of elements: 1 - cap with tide; 2 – outer sleeve; 3 – clamp.

Fastening elements that do not provide for the use of a clamp are also used. In order to speed up the processing of products, instead of clamps, front centers are used, which simultaneously perform two operations: centering the workpiece and acting as a leader (Drawing No. 4). When the product is exposed to the rear center, the corrugated notches are pressed more tightly to the sides of the part and impart a rotational movement to it. When turning hollow products, external grooved centers are used, and when using rollers, internal grooved centers are used.

Drawing No. 4. Fixing the workpiece using a driving chuck. Designation: 1,2 – centers.

The workpiece to be processed is supported on the center, and the cams are used to transmit rotation to the workpiece. Moreover, the cams are made floating for more complete fixation of the part. The mandrel is fixed using the clamping force acting between the tailstock and the front center of the lathe mechanism, which moves to the left, as a result of which the cams take the optimal position and fix the workpiece more tightly. The conical support ring has a gap, which allows it to occupy a middle position due to springs. Rotational movements of the workpiece are ensured by cams with a grooved surface.

Safe and dangerous leash cartridges

Purpose.

The self-centering three-jaw lathe chuck belongs to the class of spiral-rack self-centering three-jaw chucks with a cylindrical belt and mounting on a lathe through an intermediate flange. Self-centering spiral rack lathe chucks are designed for installation on universal lathes, turrets, and internal grinding machines. They are used in conditions of single, small-scale and mass production. Three-jaw self-centering chucks hold round and hexagonal workpieces or round rods of large diameter. Unlike wedge-type lathe chucks, they do not require time for readjustment in the case when installation to a different clamping diameter is required.

Thermal cartridge

Thermal chuck is used for the same purposes as a collet chuck. The difference lies in the principle of clamping the tool: a shrink fit is used for this in the thermo-chuck. The cartridge is heated in a special device, and its hole increases due to thermal expansion. Then the tool is inserted into it, and the cartridge is cooled (in air or in a special device). Unclamping occurs in a similar way.

The advantage of a thermal chuck is its high clamping force, which cannot be achieved in a collet chuck, much less a drill chuck. The use of such a chuck reduces vibration and significantly increases the durability of the tool.

Disadvantages: tools of different diameters require different chucks; constant cycles of heating and cooling lead to severe wear of the cartridge; Special equipment is required to change tools.

Clamping mechanism design

Another important classification of devices, affecting their design and application, concerns the assembly of the clamping mechanism. According to this parameter, chucks for lathes are divided into the following types:

• Drivers are the simplest, used for processing the center; if it is necessary to sharpen the side surfaces, gear and pin units are selected;
• Spiral self-centering - centering occurs simultaneously with fixation, which reduces the time required for preparation. The most popular lathe chucks are equipped with two, three or six holders;
• Lever - their feature is the presence of a rod with a coupling, driven by a hydraulic drive. Due to this, fastening occurs. In demand in small-scale production;
• Wedge rack - this lathe chuck is similar in characteristics to a lever chuck, but provides greater centering accuracy;
• Collet - capable of fixing only rod samples with a small diameter. Despite the low versatility, they are popular due to minimal radial runout, which improves the quality of work;
• Drilling - designed for connecting drills and other tools to the machine;
• Thermal chucks - used on the same machines as collet chucks, but they require a shrink fit to connect the tool;
• Hydraulic chucks are another alternative to collet devices. The lathe chuck clamps the tool due to the operating fluid pressure, which reduces the force required for reliable clamping.

Specifications

The chuck body is made of high quality special cast iron

Table 1

Using a lathe chuck, using straight and reverse jaws, you can clamp workpieces in the following range of sizes

The straight cam is designed to secure the workpiece to the outer surface of the shaft or to the inner surface of the hole in the workpiece. The reverse cam is designed to secure the workpiece to the outer surface.

Accuracy characteristics of lathe chuck

Fig.2.1 - Lathe chuck at idle speed

the cartridge provides the following accuracy characteristics: Radial runout a – 0.045 mm;

End runout c – 0.025mm.

By securing the workpiece in the chuck, the following characteristics can be achieved:

Scheme I:

range of fixed workpieces from 5 to 118mm;

Radial runout a at a length of 80 mm is 0.040 mm.

Scheme II:

range of fixed workpieces from 77 to 188 mm and from 160 to 250 mm;

Radial runout a – 0.045mm;

End runout c – 0.025mm.

Scheme III:

Operating principle and features

The cartridge is placed in a universal or highly specialized machine. It is needed for mounting elements on the spindle axis. They provide a reliable grip on the workpiece, and at the same time improve clamping at high speeds.

Operate in a clean, dry place, all chemical liquids that cause corrosion are removed to preserve the cartridge. Then, before work, all the coupling bolts are tightened all the way with a wrench. The next step is to fasten the cartridge element into the turning unit, tighten the bolts with nuts and turn on the machine.

It is best to start the unit at low speeds in order to check the strength of the assembly and at the same time calibrate the values ​​of the axial and radial runout at idle.

In order to secure the workpiece on the machine, a chuck with two or three jaws is most often used. At the same time, there are parts with independent movement of the cams.

These same teeth move together in a radial direction, due to which the workpiece is held in the processing zone.

The cams move through a disk, which on one part has “Archimedean spiral” grooves, and on the other side there is a bevel gear that interacts with the other wheels.

The first wheel begins to move through the key, and at the same time the disk begins to work, which simultaneously moves the cams. If they move closer to the middle of the cartridge, then the workpiece is compressed, but if, on the contrary, they move away, then the workpiece is released.

Drill chuck. How to choose ?

Self-clamping chuck

Such chucks (sometimes called quick-release chucks) also sometimes have conical elements in their design, but mostly use internal threads (this is indicated on the product labeling).

Self-clamping chuck includes:

1. A bushing with an axial hole in the form of a cone.
2. Clamping ring equipped with corrugations.
3. Frame.
4. A couple of jamming clamping balls.

The principle of operation of a self-clamping chuck is that the drill clamp is provided and maintained during the rotation of the spindle itself, which is especially useful in conditions of frequent use of the drilling machine. A drill with a conical shank of the same number is inserted into the sleeve, and it is inserted into the hole in the body. As a result, the clamping ring is raised and the clamping balls fit into the holes on the outer surface of the replacement sleeve. When lowering the ring element, the balls are placed in the holes and provide clamping of the device.

In this case, replacing the drill can be done without turning off the machine. The operator only lifts the ring, the balls move apart and release the replaceable sleeve, which is then removed from the device. Subsequently, a new replacement bushing can be installed in its place, for which the same manipulations are performed. Typically the kit comes with several split bushings having different Morse taper numbers. You can insert several parts one into one, thereby increasing the number of possible combinations.

The keyless chuck can also have a different design, used when the part already has a hole, and it is necessary to center the drill (countersink, reamer) relative to its axis. The device has a movable mandrel and a driver, which is located in a non-circular hole in the inner part of the body. The bearing assembly compensates for possible axial forces. The coupling is screwed to the mandrel, connecting it to the body, and is secured from below with a retaining ring. The spring, which is located inside the mandrel, presses it against the body. This ensures precise positioning of the chuck according to the depth of the existing hole. The chuck is removed from the spindle using either wedges (flat or radius) or an eccentric wrench.

Three jaw drill chuck

Three cams are placed in the housing at an angle that prevents self-braking of the elements. When the key, which is inserted into the corresponding hole on the body, rotates, the cage and nut begin to move. As a result, the cams are retracted, and simultaneously in the radial and axial directions. Along the axis of the chuck, a space is formed where the tool shank is placed. When the shank rests on the thrust bearing, the key is turned in the opposite direction and the cams are brought into tight contact with the conical part of the shank. At the same time, the axial orientation of the tool relative to the spindle is also carried out.

Due to the simplicity of the design and the method of adjusting the tool, three-jaw chucks are primarily used in small workshops, as well as in household drilling machines.

The disadvantage of three-jaw chucks is noticeable wear of the jaws, especially if they are heat treated to insufficient hardness.

In addition to the designs described, other types of cartridges are also used. For example, collet chucks are used to install relatively small diameter drills. In them, fixation is carried out by pressing the split sleeve, where the drill is located, with a union nut. It moves along the threads that are on the body of such a cartridge and reliably presses the sleeve against the collar of the cylindrical part of the body. Collet chucks, unlike jaw chucks, are much easier to disassemble, which facilitates the process of cleaning and repairing them.

For precision and high-speed drilling machines, chucks with a hollow shank are most effective. The upper part of such a shank is threaded, and in the lower part there is a hole into which coolant is supplied under pressure of up to 50 atmospheres. Drill chucks of the HEHA series allow coolant to be supplied through radially or coaxially located holes in the body. A peculiarity of the use of such equipment is the need for its dynamic balancing, which takes into account both the torques from the drilling machine drive and the pressure created by the coolant flow.

Jaws for two- and three-jaw mechanized wedge lathe chucks

Main design options

Lathe chucks are made of durable cast iron with a grade of at least SCh-30 or tool steel grades with a strength of at least 500 MPa.
There are various design options for lathe chucks; we will focus on the most commonly used in modern production:

Lever chuck. The clamping occurs due to the displacement of the cams with clamps due to the action of a two-arm lever. The main characteristic is the number of cams and the degree of displacement on the working disk. The disadvantages include the difficulty of setting up, especially when carrying out non-standard operations. The cams can be adjusted by moving them simultaneously using a key or by individually adjusting each clamp. This type of equipment is usually used for roughing or semi-finishing.

Wedge lathe chucks are an improved version of the lever clamp design. High accuracy of fixation is ensured by the presence of its own mechanical or pneumatic drive for each cam. It has the ability to fix the workpiece with an offset relative to the center of rotation, which makes it possible to process parts of complex configurations.

Diaphragm lathe chucks. Provide the highest fixation accuracy thanks to membranes made of elastic material. The workpiece is fixed by turning off the hydraulic drive, which leads to expansion of the membrane. Characteristic features of the design are a large number of clamps with a relatively low compression force. Therefore, the main area of ​​application of this type of equipment is finishing of parts at low rotation speeds.

Intermediate flanges for self-centering chucks

Before use, the lathe chuck must be installed and secured at the front end of the spindle, but given the difference in the design and size of the seats of lathe chucks and spindles, it is not always possible to secure the chuck directly to the front end of the spindle, for example:

• If the chuck has a centering belt (ledge), then an intermediate (adapter) flange is required to install it on the spindle, regardless of the type of spindle end
• If the chuck has a centering cone, but the size of the cone does not match the size of the centering cone of the spindle end, an intermediate (adapter) flange is also required
• If the end of the spindle ends with a thread, then an intermediate (adapter) flange is required to install any chuck on it

GOST 3889-80 (DIN 6350) Intermediate flanges for self-centering chucks

This standard applies to intermediate flanges intended for installation on the ends of spindles of metal-cutting machines with self-centering general purpose chucks.

Intermediate flanges (they are also called plan washers) are necessary for centering and fastening chucks with a centering belt (GOST 2675 type 1) on any of the 4 types of lathe spindle ends.

GOST 3889-80 Flanges must be manufactured in the following versions:

1. Version 1 – installed on the threaded ends of spindles in accordance with GOST 16868;
2. Version 2 – installed on the flanged ends of spindles in accordance with GOST 12593 under a rotary washer;
3. Version 3 – installed on the flanged ends of spindles in accordance with GOST 12595 version 1;
4. Version 4 – installed on the flanged ends of spindles in accordance with GOST 12595 version 3.

GOST 3889 Version 1. Intermediate flanges for threaded ends of spindles

GOST 3889 Intermediate flanges for threaded ends of spindles

In order to secure a lathe chuck at the front end of the spindle, it is necessary to make or purchase an intermediate (adapter) flange, which is also called a faceplate.

From the spindle side, the intermediate flange must be screwed onto the spindle thread d and very accurately slide onto the centering belt - a cylinder with a diameter of Ø d1 and a length of l mm.

On the side of the lathe chuck, the intermediate flange must have a centering belt - step D4 for precise installation and centering of the lathe chuck on the intermediate flange, and also have through holes for attaching the chuck. Obviously, for each standard size of lathe chuck there must be its own intermediate flange.

It is allowed to install 1 locking device against self-unscrewing on the intermediate flange of the design.

The lathe chuck installation process consists of the following steps:

• The intermediate flange is screwed onto the spindle thread until it stops. The hole in the flange should fit tightly onto the spindle collar
• The screws of the locking device are tightened against self-unscrewing
• Check the runout of the centering belt on the flange (D1) and the supporting end surface on the chuck side
• A cartridge is installed on the centering belt (D1) and secured with bolts
• The radial and axial runout of the chuck is checked

Example: intermediate flange for a TV-4 lathe

Intermediate flange for TV-4 lathe

An example of a designation for a flange of version 1, with a diameter of 100 mm:

Flange 7081-0592 GOST 3889-80

An example of a designation for a flange of version 1, with a diameter of 125 mm:

Flange 7081-0593 GOST 3889-80

Intermediate flange for a lathe with a threaded spindle end

GOST 3889-80 Intermediate flanges for rotary washer

GOST 3889-80 Intermediate flanges to the ends of spindles type A. Version 1

GOST 2675-80 SELF-CENTERING THREE-JAW CHUCKS

1. The standard applies to self-centering spiral-rack three-jaw chucks of accuracy classes N, P, V, A, installed on machine spindles through adapter flanges and directly on the flanged ends of the spindles.

2.Cartridges must be made of the following types:

Type 1 - with a cylindrical, centering belt and with fastening through an intermediate flange in accordance with GOST 3889-80.

Type 2 - with fastening directly to the flanged ends of the spindles under a rotary washer in accordance with GOST 12593-72;

Type 3 - with fastening directly to the flanged ends of spindles in accordance with GOST 12595-85.

1, 2. (Changed edition, amendment No. 1).

3. Cartridges of all types are manufactured in the following versions:

- with solid cams,

- with assembled cams.

4. The main dimensions of cartridges of types 1, 2, 3 must correspond to those indicated in drawing 1 and table 1.

An example of a symbol for a type 1 chuck, 200 mm in diameter with solid jaws, accuracy class H:

Cartridge 7100-0007 GOST 2675-80

The same, type 2 chuck with a diameter of 200 mm, mounted on a spindle with nominal size 5, with prefabricated jaws, accuracy class P:

Cartridge 7100-0032-P GOST 2675-80

Re-adjustable universal chucks

Designed for fastening workpieces using replaceable settings installed on the lower angle 1. The workpiece is clamped by the upper cam 2 , operating from a pneumatic drive through lever 3 . Side cams 4 serve for additional fastening of the workpiece. The cartridges are installed on the adapter flange.

Dimensions in mm