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Schaublin collets: reading a reference and choosing the right type

The number on a Schaublin collet is not its capacity. What a reference really tells you, what an article number tells you, and how the types differ.

By Julien Faivre Updated

Pinces Schaublin : lire une référence et choisir le bon type

The number W20 on a Schaublin collet is not its maximum clamping capacity. A W20 clamps up to 20 mm, but a B32 stops at 24 mm, not at 32. The number designates the diameter of the body, the one that has to match the seat in your spindle.

That is the source of half the orders that go back. Schaublin has been making collets since 1915 and the nomenclature is perfectly logical, provided you know what each part of the reference designates.

Schaublin collet of type W, rear thread almost the same diameter as the body
A collet of type W. The identifying detail is at the back: its thread is almost the diameter of the body, whereas on a B collet it is markedly smaller.

Reading a reference

Anatomy of a reference: Schaublin W20 W 20 Type : actuation mode Body diameter in mm, not the capacity A W20 clamps up to 20 mm; a B32 only up to 24 mm.
The letter and the number answer two separate questions: how the collet closes, and which seat it fits.

The article number reads the same way, and it is often the one you have in front of you: engraved on a worn collet, or copied from an old order on which the type does not appear.

Anatomy of an article number: 76-221 – 76 221 Prefix : the collet family Sequential number : cannot be deduced Here, an F32 collet. The eight prefixes of the range 71 72 74 75 77 78 80 76 A B D L P W EX/ESX F A prefix is enough to filter a search: “76-” brings up every F collet.
The prefix can be read, the sequential number cannot be guessed. To get from the article number to the exact type you need the cross-reference table in the catalogue.

First: the part or the tool?

Before the type, one question cuts the catalogue in two. Collets A, F, W, B, L, P clamp the material, that is the bar or the part in the spindle. Collets EX, ESX, ET1 and D clamp a tool by its shank, in a toolholder. The two families never cross.

For material clamping, everything then comes down to three ways of actuating a collet.

The three actuation modes cross-section, the front of the spindle is on the left Pull-back collet Push-type collet Feed collet W · B · L · P F A spindle slit collet clamping member bar or part
The pull-back collet is drawn into a tapered bore that narrows towards the rear. The push-type collet is compressed by a sleeve sliding forward against a stop nut: the face of the part does not move. The feed collet has no clamping member: closed at rest, it pushes the bar.

What size changes: the clamping force

Clamping force by type newtons, bar clamping in general application type B type W B6 B8 W12 W15 W20 W25 B32 B45 700 N 1,400 N 3,000 N 5,000 N 7,500 N 10,000 N 11,500 N 27,000 N 0 7,000 14,000 21,000 28,000
The two families interleave: a B32 clamps harder than a W25. On collets with a projecting nose, reckon on 50 to 75% of these values.

Standard or ultra-precision?

Schaublin supplies every collet in two grades of precision. The standard execution is checked by AQL 1.0 sampling and is enough in most cases. The UP execution is checked at 100% and halves the radial runout, for a price premium.

Maximum radial runout, round bores millimetres, the tolerance tightens as the diameter decreases standard UP up to 1.6 mm 1.6 to 10 mm 10 to 30 mm over 30 mm 0.010 0.005 0.015 0.008 0.020 0.010 0.030 0.015 0 0.010 0.020 0.030 mm
Values measured on the collet alone, clamping over the full length of the bore. The table does not apply to type A feed collets.

The 0.1 mm rule. A pull-back collet opens very little. It is made to clamp its nominal diameter, and going more than 0.1 mm below it degrades concentricity. For an intermediate diameter, take the collet to size, not the next one up.

The bore: shape and finish

A collet does not necessarily clamp round stock. Square and hexagon are standard bores at Schaublin, just like round, and can be ordered from the catalogue. Any other profile is made to order, with slitting adapted to the profile.

Mind the dimension you pass on: on a profile it is the measurement across flats that counts. To know which collet size can take it, that has to be converted into the diameter across corners.

Shape Code Dimension to give Equivalent diameter Availability
Round ø diameter — Standard
Square C across flats C D = C × 1.414 Standard
Hexagon S across flats S D = S × 1.155 Standard
Special profile sketch per drawing to be calculated To order, adapted slitting

A hexagon of 10 mm across flats therefore calls for a collet capable of an 11.55 mm bore; a 10 mm square, a collet of 14.14 mm. That is why a profile consumes one collet size more than the nominal dimension suggests.

A profile is paid for in concentricity. A standard profiled bore allows 0.060 mm of radial runout, against 0.020 for a round bore of the same size, and 0.040 even in UP quality. If concentricity is critical, pick the part up again on a round bore.

That leaves the finish of the bore, which decides the grip. Schaublin quantifies the difference through the coefficient of friction between the collet and the part.

Finish Available from Coefficient of friction Trade-off
Smooth all dimensions 0.05 to 0.30 Does not mark the part
Grooved ø 9 mm round · 14 mm profiled 0.20 to 0.40 Grips markedly better, marks slightly
Serrated ø 14 mm 0.30 to 0.60 Grips best, marks most

Going from smooth to serrated can multiply friction by six, and therefore the torque transmissible before slipping. On type F push collets, incidentally, round bores are smooth up to ø 8.99 mm and grooved as standard from 9 mm.

Tool clamping: EX, ESX or D

Type Standard Clamping range Use
EX DIN 6499-A nominal diameter only (ISO h12) Ultra-precise concentricity
ESX DIN 6499-B 0.5 to 1 mm downwards Standard, one tool per range
ET1 — standardised dimensions Tapping, integrated axial compensation
D Schaublin standard nominal diameter, UP quality High-speed machining and ultra-precision

All of them have an extraction system that releases the collet from its seat as the nut is loosened. Type D is Schaublin's answer to high-speed machining: a shallower taper and a finer nut thread, which raises the clamping force and maintains it at high speed. A more stable and safer system than ESX or EX in fast rotation.

Beyond the round collet

The same collet body serves as the basis for a whole family of tooling, which saves tying up a spindle for a special case. The rough-bored funnel collets are machined to size to clamp an external shoulder, the step collets do the same from the inside, the expanding mandrels hold a part by its bore, and the tapping collets provide axial compensation. All of them draw on the F, W or B bodies.

Discover the complete Schaublin catalogue

Collets for material and tool clamping, funnel and step collets, expanding mandrels, nuts, depth stops and HSK toolholders: the full range is online, with the diameters and the standard and UP qualities available for each.

See the Schaublin catalogue

So, which collet type is in your spindle? Tell us in the comments.

Technical data from the Schaublin catalogue 476-4800, edition 06/2022 (Schaublin SA, Delémont). Check the type and the body diameter on your spindle before ordering.

Frequently asked questions

Which Schaublin collet fits a Schaublin 102 lathe?
A Schaublin 102 lathe takes W20 or W25 depending on its spindle nose; a W25 spindle accepts W20 collets with a reduction adapter and the matching clamping key.
How can a Schaublin W collet be told apart from a B collet?
By the thread: on a W collet the thread diameter is almost equal to that of the body, whereas on a B collet it is markedly smaller.
What does the prefix of a Schaublin article number mean?
The prefix designates the collet family: 71 for A, 72 for B, 74 for D, 75 for EX and ESX, 76 for F, 77 for L, 78 for P and 80 for W.
Are Schaublin collets available with square or hexagon bores?
Yes, square and hexagon are standard bores at Schaublin; the dimension to pass on is the measurement across flats, a square of C mm corresponding to a diameter of C times 1.414 and a hexagon of S mm to S times 1.155.
What is the difference between an ESX collet and an EX collet?
The ESX collet, to DIN 6499-B, covers a clamping range of 0.5 to 1 mm downwards, whereas the EX collet, to DIN 6499-A, is made in ultra-precision quality and clamps its nominal diameter only.
Does the number on a Schaublin collet correspond to its clamping capacity?
No: the number designates the diameter of the collet body. A W20 does clamp up to 20 mm, but a B32 stops at 24 mm of capacity.

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