The Bernardo 3-jaw steel chuck PO3-250/D8 is a lathe chuck for professional use, with a diameter of 250 mm and a weight of 32 kg. Krollit, official Bernardo distributor since 2007.
- Chuck size: 250/D8
- Diameter: 250 mm
- Taper: 8
- B: 89 mm
- D (max.): 139,734 mm
- E: 76 mm
Who uses the 3-jaw steel chuck PO3-250/D8 and for what
Mechanical workshops and artisan turners use the 3-jaw steel chuck PO3-250/D8 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 3-jaw steel chuck PO3-250/D8 is part of the Bernardo lathe chuck range, distributed in Italy by Krollit since 2007. The Bernardo range includes models of various categories and performance: 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 is the 3-jaw steel chuck PO3-250/D8 for?
The 3-jaw steel chuck PO3-250/D8 is recommended for the following professional profiles:
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Mechanical workshops and artisan turners: Secure clamping of round or hexagonal workpieces on a metal lathe during turning, drilling, and grooving operations.
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Users with a Bernardo lathe with a compatible flange: Original replacement or upgrade for Bernardo range lathes (profi, hobby, etc.) with A2 attachment compliant with DIN 55029.
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Irregular or non-round workpieces: For non-symmetrically centered workpieces, consider 4-jaw independent chucks or universal platforms.
Technical specifications
| Diameter |
250 mm |
| Taper |
8 |
| B |
89 mm |
| D (max.) |
139,734 mm |
| E |
76 mm |
| F1 |
171,4 mm |
| Cam-lock studs |
6 |
| Chuck size |
250/D8 |
| Max. speed |
3500 rpm |
| Approx. weight |
32 kg |
Frequently Asked Questions
When to use a 3-jaw chuck?
Self-centering 3-jaw chucks are for cylindrical, hexagonal, and 3-6-9-12 sided workpieces. The jaws move together with a single key (self-centering).
It is the most common chuck on lathes: quick clamping of symmetrical workpieces, typical concentricity precision of 0.03-0.1 mm depending on the body material (steel = better precision, cast iron = standard).
Why a steel chuck compared to cast iron?
Steel chucks (PO series) offer superior concentricity precision (0.01-0.03 mm) and greater wear resistance in intensive machining.
Ground steel: higher weight, but smaller dimensions for the same nominal diameter. Suitable for series production and precision turning on treated steels or hard alloys.
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 size of the body, not the workable workpiece. The clamping capacity depends on the jaw opening (typically 60-70% of the nominal Ø).
What does the D8 mounting indicate?
The D8 code (Camlock according to DIN 55029) identifies the size of the lathe spindle nose: D3-D5 for small lathes, D6-D8 for medium, D11-D15 for industrial.
Check the mounting of your lathe before purchase: the interface flange must exactly match the code. Camlock = quick closing with cams, disassembly in 30 seconds without tools.
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.
