Mandrels and plugs for installation and fastening of workpieces on the internal machined surface

Mandrels with one-sided collet

Mandrels with a single-sided collet are used for light work. The base surface of the workpiece must be processed taking into account the expansion of the collet to 0.5 mm. Recommended hole diameters for workpieces are 15 mm and above.

Dimensions, mm

D	d (additional deflection for A/C)	d1 (additional deflection for A/G)	d2	d3	L	l1	l2	l3
15—20	6,5	17	22	27	36	19	7	17
21—25	8,5	23	28	33	47	22	10	20
26—30	10,5	28	33	38	54	24	12	22
31—35	10,5	33	38	43	61	26	16	24
36—40	12,5	38	43	48	74	29	20	27
41—45	16,5	45	50	55	82	32	20	30

Types of collets

Collet clamping devices are structurally divided into:

retractable – clamping occurs when the collet is recessed in the clamping mechanism;
retractable – fix the workpieces when they are pulled out of the chuck;
stationary - they clamp the part by pushing the conical hole of the clamping device onto the conical working surface of the stationary collet.

By purpose they are divided into:

feeders – grab and push part of the bar into the processing area;
clamping - they only fix the workpiece in the chuck (similar to the collet of a collet pencil), without performing other functions.

Mandrels with smooth collet

Mandrels with a smooth collet are used for light to medium work. The base surface of the workpiece must be processed taking into account the expansion of the collet to 0.5 mm.

Dimensions, mm

D	d	d1	L	l1	l2
20-25	9,8	M20x1.5	40	40	20
26—38	12,8	M24X2	55	55	25
39—54	17,8	M36x2	80	80	32
55—78	27,7	M48x3	115	115	43

Collet chuck design

The collet chucks under consideration for milling machines are structurally composed of three main elements:

The housing is the base of the equipment and is intended for installation in the machine, as well as for fixing the collet with the cutting tool. In the part where the collet is inserted, it has a cone-shaped shape.
Collet - is a sleeve made in such a way that the inserted shank of the cutter is evenly compressed after tightening the nut and thereby securely fixed. The use of collets with different internal diameters allows the same chuck to be used with many different cutters and other cutting tools.
Clamping nut - designed to clamp the collet with the nozzle inside the body cone, as a result of which the cutter is crimped and fixed for the working process. The nut has slots for a special wrench supplied in the kit.

This design of a collet chuck for a milling cutter has its own characteristics, advantages and disadvantages.

Self-centering collet plugs

Self-centering collet plugs are used for medium-sized jobs. The collet is expanded by pressure from the center. The base surface of the workpiece must be processed taking into account the expansion of the collet to 0.5 mm.

Dimensions, mm

D	d	d1	L	l	l1	l2
30—34	26	M20x1.5	65	32	27	16
35—39	33	M20x1.5	65	32	27	16
40—44	37	M24x2	75	38	31	17
45—49	43	M30x2	80	38	31	22
50—54	48	M42X3	90	48	41
55—60	53	M42X3	90	48	41

Scope of application of collet chucks and main advantages

Fixing equipment with replaceable collets is widely used for installing cutters and axial workpieces on various types of metal-cutting machines. It is also used on CNC machines due to its high clamping reliability and quick tool changes. The collet fastening is optimal for fixing rods and other cylindrical parts. Its use is also convenient for re-fastening a machined part.

The main advantages of the collet fixation method:

Minimum radial runout of the workpiece.
High-precision centering of the part.
Easy installation without keys.

The main disadvantage of collet chucks is the limited diameter of the shanks of the installed tools and workpieces. To expand the standard sizes of the tool, it is possible to use adapter bushings.

Mandrels with double-sided collet

Used for light work. The base surface of the workpiece must be processed taking into account the expansion of the collet to 0.5 mm.

Dimensions, mm

D	d (additional deflection for A/C)	d1	TO	l	l1	L
40—44	20	28	10	62	35	90
45—49	20	30	15	70	35	100
50—54	25	33		80	45	110
55—59	30	38		80		110
60—65	30	46	20	100		125

Appointments

A collet chuck is a mechanism designed for rapid clamping of cylindrical and other sections (tetrahedral, hexagonal, etc.) rods, workpieces or cutting tools. More often used in finishing operations.

A collet is a hardened steel bushing (or made of another elastic material) with incomplete cuts on the sides, forming petals with spring properties (returning to their original position). These properties are used in the basics of the clamping process - unclamping and centering the workpiece in the working area of the machine.

The effect of introducing this type of clamps is manifested when:

restoration of cutting edges of drills, taps and cutters;
production of parts from rod material, pipes and precision castings;
fixing workpieces with the reverse surface;
working on pre-processed material.

The use of leveling inserts solves the problem of the workpiece surface not matching the dimensions of the collet clamping mechanism.

Collet mandrels for stepped holes

Used for light work. The base surface of the workpiece must be processed according to 2 or 3 accuracy classes.

Dimensions, mm

D	D1	d (additional deflection for A/C)	d1	d2	d3	TO	l1	l2	l3	L
25—29	By workpiece	12	15	D— 1	22	8	32	24	80	105
30—34		15	18,5		28	12	45	33	100	125
35—39		20	20		33	15	55	41	125	150
40—44		20	25		37	20	60	51	140	165
45—48		25	30		42	20	60	61	160	185
50—54		25	35		47	20	60	66	170	200
55—60		30	36,5		51	20	65	69	182	210

Features of collet chucks

The main feature of the collet chuck, which is its advantage over other types of clamping equipment, is the uniform fixation of the working tool. The collet, under the influence of the nut, comes into contact with a large area of the cutter shank, which significantly reduces the level of vibration and deviation of the tool from the axis under lateral loads. All this together increases the accuracy of metal processing, allowing you to work with small parts while maintaining the necessary parameters of the finished product.

Another advantage of collet chucks for routers is the versatility of the equipment. Due to the fact that collets of different diameters can be inserted into the same chuck, it is possible to work with a large assortment of cutters without replacing the body itself. All this expands the possibilities in metal processing and also significantly speeds up the work process. The procedure for changing the cutting tool and collet also does not take much time - the nut can be unscrewed quickly enough by hand after loosening it with a wrench.

Mandrels with collet tightening through the spindle

Used for medium work. The base surface of the workpiece must be processed taking into account the expansion of the collet to 0.5 mm.

Dimensions, mm

D	d(additional deflection A3/C3)	d1	d2	d3	l1	l2	l3
45—49	26	29,5	60	40	35	25	175
50—54		35,5	60	45
50—59		37,5	70	50
60—64		41,5	70	54
65—70		45,5	80	58	40

Types and principles of operation of chucks

Collet chucks are used mainly when processing cold-rolled rods or other metal products that have an already machined surface.

Structurally, cartridges can be classified according to functionality:

with a fixed mechanism;
with retractable mechanism;
with retractable mechanism.

Each design has its own characteristics. The feeding type is made in the form of a steel sleeve with 3 cuts forming petals that have a springing effect.

Drawing No. 1 of the main spindle collet

Type F

Collets type F - clamping the main spindle are used to secure the workpiece.

Drawing No. 2 of the counter-spindle collet

Type LN

Collets type LN - counter spindle are produced elongated, size E depends on the standard size.

Drawing No. 3 collet type R

Type R

Type R – are pull-type collets.

Drawing No. 4 collet type T

Type T

Type T - clamping.

Drawing No. 5 collet BF

Type BF

BF type feed collet - designed for bar feeding.

When installed on the machine, the feed collet is threaded onto the pipe with the help of which it is fed into the working area. It is necessary to take into account the design feature - the size and shape of the collet, which must necessarily correspond to the profile of the bar being processed.

In preparation for processing, the rod moves through the petals, which, due to their design features, tightly hold the workpiece. During processing, when feeding the workpiece, the adhesion force between the petals and the product increases due to rotation. The principle of operation of the clamping elements is based on strengthening the adhesion of the petals to the workpiece during rotation of the working mechanism. Bushings with 3 petals are used for processing products up to 3 mm, four – up to 80 mm, six – over 80 mm. Typically, collets have an angle at the apex of the cone equal to 30º.

Collets for shaft 2 mm (0.1-3 mm) for micro drill

When processing thin rods, collets equipped with springs are used to increase the clamping force of the jaws. When increasing the diameter of the workpiece being processed, designs are used that are equipped with special inserts selected according to the dimensions of the product. Collet clamps are also used when machining with a drill, cutter or tap. The sleeve is fixed in the chuck with a nut, and the cutting tool is fixed directly in the collet. When fixed with a nut, the internal volume of the hole where the workpiece is installed is reduced, thereby increasing the force holding the rod stationary.

Cartridges of this design also have their drawbacks. First of all, the requirement that the shanks of the tool used must match the characteristics of the collets used. At enterprises, the most widely used collets are the ER type, which constitute the largest number in the total volume of tools used.

When performing complex work on the manufacture of products, various collets are used, indicating all sizes and technology for performing work operations, but often it is necessary to combine equipment or make the necessary collet chuck with the required characteristics with your own hands.

Video review of a lathe collet chuck

Collet mandrels with adjustable clamp

Used for light work. The base surface of the workpiece can be machined with large deviations.

Dimensions, mm

D	d	d1	d2	d3	TO	L	L1	l	l1	l2	l3	l4
48—54	19	25	44	38	25	235	170	40	85	30	15	15
55—64	20	25	50	42	25	250	185	40	100	30	15	15
65—74	25	30	60	50	30	290	220	60	110	45	20	20
75—84	30	40	70	60	35	320	250	60	130			20
85—95	35	40	80	70	35	365	275	70	145			25

How to make your own collet chuck

When making various products with your own hands, situations arise when the available equipment does not allow you to perform the necessary operations. It is required to produce a collet chuck that meets the requirements, with the product being manufactured according to the developed sketch.

All work must begin with the preparation of a sketch with the elaboration of all the necessary details. The sketch of the chuck allows you to take into account all the features when making the necessary equipment and clamping mechanism with your own hands.

When making collets with your own hands, you need to consider several features:

the internal diameter of the collet is equal to or less than the minimum diameter of the part;
in a collet, an increase in the internal diameter is possible due to the expansion of the petals;
to increase the production of adjustable collets after setting and improve the quality characteristics, additional grinding of the conical and guide parts of the collet is necessary;
It is necessary to take into account that during long-term operation the elasticity of the collet blades is lost, as a result of which breakage may occur.

Expanding mandrels with rollers

Used for medium work. The clamping is carried out by jamming the rollers between the workpiece and the mandrel. The base surface of the workpiece can be processed according to 8-9th accuracy classes.

Dimensions, mm

D (additional deflection according to WITH )	D1	D2	d (additional deflection according to C)	L	l	l1
25	19	30	6,05	100	75	30
30	22	34	8,05	120	90	40
35	27	40	8,05	120	90	40
40	30	44	10,05	135	100	60
45	33	50	12,05	155	120	60
50	36	54	14,05	170	130	70

How does a collet clamp work?

Made in the form of a sleeve with a truncated cone having a hole of a given configuration (round, tetrahedral, hexagonal, etc.). Cuts are made along the collet, forming clamping blades with conical working surfaces.

The operating principle of the device is as follows:

when clamping, into the hole formed by the clamping petals: the workpiece is inserted;
the cartridge is screwed into the thread;
the conical surface of the cartridge moves onto the working surface of the collet;
the petals compress, capturing and centering the workpiece; the device clamps the object.
The part is removed by rotating the chuck in the opposite direction and removing its force from the surface of the collet blades.