The Three-Jaw Chuck - 6: Soft Jaws
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WARNING: Machine tools present a safety hazard. Improper operation can result in severe injury. These topics are for non-laboratory study only and are not to be used in conjunction with the operation of any tool or machine described herein. Never use a machine tool without the supervision of a qualified instructor.

Soft jaws are machinable jaws. Why would you wish to machine them? Remember earlier in this topic when it was expressed that 3-jaw chucks wear out? that the concentricity of 3-jaw chucking may not be dependable?

Machining your own set of soft jaws remedies this problem. If you can machine your own diameter into a set of jaws then the part that is chucked by those jaws is guaranteed to run as concentric as the bearing of the lathe spindle! That is the purpose of soft jaw machining. To insure concentricity.

Basically, the standard jaws are removed and a set of aluminum or mild steel jaws are bolted onto the chuck where the standard jaws used to fit.

It is important to make a plug for the new set of machined jaws. A plug is turned to a diameter close to the diameter you wish hold in the new soft jaws. Prior to machining, the jaws should be tightened around the plug towards the rear of the soft jaw set. This will provide rigidity while the jaws are machined and will insure that clamping pressure and scroll looseness are removed while turning.

It is also a common practice to preserve special soft jaws in case the part is often machined. The setup would be made quicker if new jaws did not have to be made.

Machinists often will stamp the part number and corresponding chuck onto the soft jaws so that easy identification can be made.

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label: three jaw chuck advaantages, disadvantages, mounting, replace jaws, soft jaws, mounting styles