Overview

The Autobox K12 series 4 jaw self centering chuck mounts to your lathe's headstock spindle nose and grips round or square stock using all four jaws simultaneously. Unlike a 4-jaw independent chuck — where each jaw is adjusted separately — the K12 self-centering scroll mechanism moves all four jaws in unison with a single wrench, delivering quick, repeatable centering without dial-indicator setup. Available in 3-inch (80 mm), 4-inch (100 mm), and 5-inch (125 mm) diameters to suit mini lathes through medium bench lathes.

Available Options

• 3 inch (80 mm) — K12-80 — $64.95 — suited to 7x10 and 7x12 mini lathes; compact footprint for small-bore turning
• 4 inch (100 mm) — K12-100 — $79.95 — most popular size for 7x14 and 8x16 mini lathes; balanced capacity and rigidity
• 5 inch (125 mm) — K12-125 — $94.95 — for medium bench lathes; larger through-bore capacity for longer stock

Key Features

• Simultaneous 4-jaw scroll drive: one bevel pinion turns the scroll, moving all four jaws together — faster setup than a 4-jaw independent chuck
• K12 series construction: hardened scroll plate and jaw serrations; body material matched to K12 industry standard for chuck runout ≤0.05 mm (0.002")
• Reversible jaws: internal jaws for gripping shaft OD; flip to external jaw configuration for larger-diameter OD or face-plate work
• Four-jaw grip on square stock: four contact points give more secure grip on square bar than a 3-jaw, with less risk of jaw marks on round stock than an independent chuck
• Chuck key included: T-handle bevel-drive chuck wrench included with each size; fits all four pinion sockets
• Three sizes, one product page: select 3", 4", or 5" diameter from the variant dropdown — same K12 mechanism, scaled to your machine

Specifications

Compatibility

This chuck mounts to the lathe headstock spindle nose via a bolt-on back plate. A matching adapter back plate is required and sold separately — the chuck does not mount directly into the MT3 headstock taper. Select a back plate matched to your specific spindle nose thread and register diameter.

Compatible lathe models (with appropriate adapter back plate):

• Sieg C2 / SC2 / C3 mini lathes (MT3 headstock)
• Harbor Freight 7x10 #93212 and 7x12 #44142 (MT3 headstock)
• Grizzly G0602, G0765 (7x14), and G8688 (7x12) (MT3 headstock)
• LittleMachineShop HiTorque 7x16 (MT3 headstock)
• Autobox 7x14 and 8x16 mini lathes (MT3 headstock)
• South Bend 9" lathe (MT3 headstock)
• Jet BD-X series bench lathes (MT3 headstock)
• Atlas / Craftsman 12"x36" (MT3 headstock)

Not sure if your lathe's spindle nose matches? Message us with your lathe model — we'll confirm the correct back plate before you order.

What's in the Box

• 1 × K12 series 4-jaw self-centering chuck (size as selected)
• 1 × T-handle chuck wrench (fits all 4 pinion sockets)
• 1 × Set of jaw mounting hardware

Note: Adapter back plate is NOT included. A back plate matched to your spindle nose thread and register is required for installation.

Frequently Asked Questions

Q: What is the difference between a 4-jaw self-centering chuck and a 4-jaw independent chuck?
A: In a self-centering chuck (this K12 series), all four jaws move simultaneously through a single scroll gear — turn any of the four bevel pinion sockets and all jaws tighten or open together. This centers round or square stock automatically and quickly. In a 4-jaw independent chuck (our K72 series, sold separately), each jaw is adjusted individually using its own screw. Independent chucks allow precise off-center or eccentric workholding and can grip irregular shapes, but require a dial indicator and more setup time. If you mostly turn round or square bar and want fast centering, choose this self-centering K12. If you need off-center or irregular workholding, choose the K72 independent chuck.