# What are "soft jaws" and how and why are they used?



## HMF

Newbie question: What exactly are "soft jaws" and why would you use "soft jaws" in a lathe chuck as opposed to normal hardened jaws?

Thanks,

Nelson


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## Tony Wells

I use soft jaws quite a bit. Soft jaws are simply jaws machined to fit a chuck in place of the hardened and ground factory jaws, typically on a 3 jaw, that are bored (or turned) to fit closely on a machined surface cut on a previous operation. They can incorporate a shoulder to "stop" against to gain close repeatability for length/depth operations. They can be shop made, or bought. 

I respect all the effort shown by guys doing their level best to achieve low TIR on their chucks, but for production work in particular, a set of soft jaws is the more economical approach (IMO). Plus they leave very little marking of the finished surfaces. They are of no use on rough stock.


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## Frank Ford

I'm really big on soft jaws, you bet.

Here's the classic, in the milling machine vise, holding knurled pieces for drilling and tapping. I machined the recess to fit the part exactly, so there's no damage no matter how hard I squeeze:





I made up sets of "disposable" soft jaws to fit various vises, so I can slip them in for more causal use without having to take off the hard jaws:




When I got my new 6" Wilton banch vise, the first thing I did was remove the hardened toothy steel jaws, and replace them with cold-rolled steel soft jaws, so the vise would take the scars more than my work. I V-grooved one jaw horizontally, and the other vertically, to hold round items, and while I was at it, I made them bigger, too:




I made up a few sets of aluminum pieces with magnets, so I can stick 'em on any vise jaw for soft gripping:


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