The Bernardo 4-jaw chuck DK12-250 is a lathe chuck for professional use, weighing 28.7 kg. Krollit, official Bernardo distributor since 2007.
- D - Chuck size: 250
- D1: 200 mm
- D2: 224 mm
- D3: 80 mm
- h: 120 mm
- H1: 80 mm
Who uses the 4-jaw chuck DK12-250 and for what
Mechanical workshops and artisan turners use the 4-jaw chuck DK12-250 as a clamping accessory on metal lathes, ensuring secure clamping and centering of the workpiece during turning, drilling, and grooving operations.
Its place in the Bernardo range
The Bernardo 4-jaw chuck DK12-250 is part of the Bernardo lathe chuck range, distributed in Italy by Krollit since 2007. The Bernardo range includes models of various categories and performances: to choose the right machine for your use case, you can consult the Bernardo catalog on Krollit or contact customer support for selection assistance.
Krollit logistics and support
Shipping 3-5 business days from Krollit warehouse for spare parts and accessories. Customer support in Italian available for technical documentation and compatibility verification with the reference machine. Krollit has been an official distributor since 2007.
Who the 4-jaw chuck DK12-250 is for
The 4-jaw chuck DK12-250 is recommended for the following professional profiles:
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Mechanical workshops and artisan turners: secure clamping of round or hexagonal workpieces on metal lathes during turning, drilling, and grooving operations.
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Users with a compatible flanged Bernardo lathe: original replacement or upgrade for Bernardo range lathes (Profi, Hobby, etc.) with A2 spindle nose according to DIN 55029.
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Irregular or non-round shaped workpieces: for non-symmetrically centered workpieces, consider independent 4-jaw chucks or universal faceplates.
Technical specifications
| D1 |
200 mm |
| D2 |
224 mm |
| D3 |
80 mm |
| h |
120 mm |
| H1 |
80 mm |
| h |
5 mm |
| Mounting screws |
6 x M12 |
| D - Chuck size |
250 |
| Max. speed |
1600 rpm |
| Weight approx. |
28.7 kg |
Frequently asked questions
When to use a 4-jaw chuck?
Self-centering 4-jaw chucks are for square and 4-8 sided workpieces. The jaws move together with a single key.
The self-centering 4-jaw chuck (not independent jaw) clamps square or octagonal workpieces symmetrically. For off-center (eccentric, asymmetrical) clamping, independent jaw chucks are needed.
What material is the chuck body made of?
The material is indicated in the title: steel (PO series) for maximum precision, cast iron (DK/PS series) for standard use.
The choice depends on usage intensity and required tolerance: steel for production and precision, cast iron for general use.
What workpieces is the Ø 250 mm diameter suitable for?
Suitable for medium workpieces (max Ø ~220 mm): professional lathes.
The nominal diameter of the chuck indicates the maximum body size, not the size of the workable workpiece. The clamping capacity depends on the jaw opening (typically 60-70% of the nominal Ø).
How do I check compatibility with my lathe?
Check the type of spindle nose mounting (Camlock D3-D15, or threaded M-mount) and the corresponding diameter.
On modern lathes, Camlock mounting is the most common. On older lathes, there may be a threaded (M-) or flanged mount. The lathe's technical documentation indicates the exact type.
How is chuck precision maintained?
Regular cleaning of the spiral mechanism, periodic lubrication with specific chuck grease, concentricity check every 6 months with a dial indicator.
A jaw that moves with difficulty indicates chips or rust in the mechanism: disassemble, clean, and grease. Concentricity is checked by mounting a ground bar and measuring with a dial indicator: acceptable tolerance 0.03-0.1 mm depending on the model.
