3D printable Longworth chuck (3 and 4 jaw versons)
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Credit for the movement should go to the late Mr. Longworth of the Hunter Valley Woodturning Club, New South Wales, Australia.

Thanks to Hexitex for turning Mr. Longworth's desgin into a printable design.

All the files are oriented and scaled for printing already.


I Reduced its diameter to 85mm and changed it to a three jaw design. I then designed a system to lock it with out a wrench.

How the lock works

The front face is now supported by three short lengths of 5/16" (8mm) smooth rod that go through large holes in the guide and sit against the base. When you turn the lock ring it turns the planets/nuts that pull the guide back and it pulls the screws holding the jaws back against the now supported face.

( you could eliminate the smooth rods by making the outside of the face extend back far enough to rest on the lip of the base. )

jun 10/11 . Added jaw_guide.stl It keeps the jaws aligned while tightening.

jun 9/11 . Replaced jaws with angled jaws inspired by MarkU's design thingiverse.com/thing:9186 except mine are sloped on both sides so only one set is needed.


--Four jaw version--

Simplified keyless chuck NOW WITH FOUR JAWS !!!!!!!!

This is untested but based on a working design.

I started over this time to guarantee symmetry.

Removed the need for smooth metal rod.

Increased thickness of face plate.

Added fourth jaw.

Increased ring gear strength.

Removed the need for machine screws with screw head or socket head. You can now use hex head bolts.

Only uses 8 machine screws / bolts with nuts.

Eight washers optional. (under planet gears and under the heads of the sliding jaw bolts)

Four springs optional. (between piston and base


Turn off all extra shells when printing the gears and lock ring so you end up with solid teeth.


six no.6 machine screws 2" long
six no.6 nuts.
one 5/16 nut (8mm nut)
three small thin washers
three pieces of 5/16 (8mm) smooth rod cut to 1.125" (28.5mm)
three springs (optional)

Test assemble all pieces and sand, shave, drill anything that causes friction.

Final assembly instructions

1) Install three screws in countersunk holes of guide. (slide springs over protruding screws)

2) Install three screws through slots in the guide the opposite direction as previous screws.

4) Install 5/16" (8mm) nut in the center of the base.

5) Install guide in to base being sure screws slide easily through holes in base.

6) Install nuts in planetary gears.

7) Install one planetary gear. You may want thin washers under the gears

8) Install lock ring and the second planetary gear.

9) Install third planetary gear by turning the last screw with a screwdriver.

10) Tighten all planetary gears evenly using screwdriver.

11) Glue screw heads to guide to ensure they don't turn any more.

12) Cut three pieces of 5/16 (8mm) smooth rod 1.125" (28.5mm) and slide them into holes in the guide.

13) Install face over the three screws protruding from slots in the guide.

14) Slide Jaw guide over protruding machine screws.

15) Install nuts in jaws and screw them to the screws protruding through face.

16) Loosen lock ring three turns.

17) Tighten jaw against the face until they are even.

18) Tighten lock ring until jaws are close to the face.