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Getting a Grip on Four-Jaw Lathe Chucks

How a chuck grips

How a chuck grips

Chuck jaws either contract around a turned spigot (round tenon) or expand into a hollowed-out recess. In contracting mode, the jaws commonly supplied with chucks grip spigots from 1 1/2" to 3" in diameter. These same jaws expand into turned recesses from 2" to 3 1/2" in diameter.

Because chuck jaws form a circle when completely closed, they make continuous contact when contracting around a spigot or expanding into a recess that is just slightly larger than the diameter of the circle, as shown right. This provides the greatest holding power and safest operation. As the jaws approach their maximum open position they make only point contact with the workpiece, as shown right. Gripping only at these points (eight in contracting mode, or four in expanding mode) is less secure and risks marring the wood. Manufacturers offer accessory jaws to cover a wide range of gripping diameters.

When turning, be careful of chuck jaws adjusted near their maximum diameter. The farther open the jaws, the more they extend beyond the chuck body, and if touched, the more likely they are to cause injury.


Continued on page 5:  Turning a bowl with a four-jaw chuck

 

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Comments (4)
7525979741
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
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 Sears says this model is obsolete any brand might as lon as the thread pattern match.Can some one help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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