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Getting a Grip on Four-Jaw Lathe Chucks

Shape the bottom
Cut away of round bowl
Enlarge Image
Dovetail jaws contracting around
a spigot
When forming a spigot at
the bottom of a bowl, match the angle
of the outside edge of the spigot to the
angle of the jaws.

Shape the bottom

When shaping the outside of a bowl, form its bottom to fit your chuck jaws so you can reverse the blank, grip it with the chuck, and form the inside. For contracting dovetail jaws, form a dovetail spigot as shown right. Cut the inside corner where the spigot meets the bowl body crisp and clean to provide a positive gripping corner for the chuck jaws. Leave a flat bearing surface for the jaw ends. Because the jaws pull in on the spigot as well as squeezing it, make the spigot slightly shorter than the jaw depth, so it does not bottom out. Sand and finish as much of the outside of the bowl as possible.

The same jaws that contract onto a spigot also will expand into a recess hollowed out in the bottom of a bowl, as shown below right. When planning the shape of your bowl, leave extra thickness in its bottom to accommodate this recess. Make it about 1/8-1/4" deep, cleanly cut, and with its edge following the shape of the jaws. Leave sufficient wood around the recess to support the outward force exerted by the expanding jaws. Gripping the bowl in this manner allows you to completely form the outside, including its bottom. With the outside of the bowl formed, sand it and apply a finish.

Generally speaking, contracting onto a spigot provides the greatest holding power. However, for turnings of large diameter but shallow depth, such as a large platter, expanding into a recess gives better results. Regardless of how the chuck holds the workpiece, be sure to periodically check its tightness.

Continued on page 7:  Now form the inside


Comments (7)
brcollectibles wrote:

I think that oneway in Canada made the ist of these. I never did much turning till I got the oneway chuck. There is only so much you can do between centers.

1/28/2016 10:25:52 AM Report Abuse
nelsondefelixy wrote:

I have just bought a 3" 4-jaw chuck, thanks for this article a guide for a beginner like me, by the way i let a machinest make an adapter to fit on the spindle of my lathe, Nelson Defelix-Iloilo City, Philippines,12-3-15, 8:30pm

12/3/2015 06:31:02 AM Report Abuse
rwm50 wrote:

myplace i have the same unit, you need a 1" + 10 tpi thread type chuck

4/3/2013 05:31:05 PM Report Abuse
Stackman wrote:

I have a 4 Jaw chuck ordered at Busy Bee Tools for my Craftsman lathe. 3/4 X 16 TPI tread pattern.

11/27/2011 10:09:28 AM Report Abuse
mcplace wrote:

I need a 4jaw chuck for a Sears Craftsman wood lathe model# 351.217150 where can I find one. Sears says this model is obsolete any brand might as lon as the thread pattern match.Can some one help

4/23/2011 12:50:03 PM Report Abuse
helmich1 wrote:

Very informative! Metalworking 4 jaw chucks work differently, but that is another ballgame.

3/24/2011 10:38:22 AM Report Abuse

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