Home Forums Hunting & Shooting Gunsmithing Lathe question

The beauties of soft jaws on a lathe are several. First and foremost, they are amazing problem-solvers. Parts that are a pain to perform certain operations on with stock jaws- thin discs needing a facing cut comes to mind- are trivially easy and repeatable. Or, parts that will get the finish marred by hardened jaws. Or, parts where you need to absolutely maximize the the number of, and/or and size of surface-area contact points of; I have a big (12 lbs?) out of balance casting I work with where that’s critical. Soft jaws are also incredibly accurate (concentric).

The chuck in the picture is an Adjust-Tru type, meaning the chuck body itself has some limited adjustment range to bring a part to true. But for illustrative purposes let’s imagine a fixed chuck; you put it on the spindle, and it’s fixed in place. What you get is what you get as far as concentricity.

(that’s kind of an abomination; all scroll chucks should be Adjust-Tru type. But I digress. Most are NOT)

If our subject fixed chuck has 2-piece jaws you can take the top jaws right off. You can see on the pics of mine with the aluminum jaws for easy visual contrast how the top jaw fits into the master jaw. It locks very precisely to the master jaw- it’s a very light press fit. Zero wiggle between master jaw and top jaw- that’s important. I make mine from bar stock and when milling that cross piece section I leave it about .0005” over and do the final fit with a few strokes of a fine file. Each jaw is numbered to match the number stamped in the master jaw. You can find the dimensions for master and soft jaws online- it’s a standard. For that matter you can buy them, but I make my own. This is an uncut, mild steel soft jaw, one of a couple sets (of 3)on my shelf, waiting to be needed.