I didn't take as many pictures as I'd have liked for this little presentation, but I think there are enough to get the general view of this project.

From time to time I make batches of small thumbscrews or other threaded items, and I've wanted to have a good way to hold them up to a buffing wheel. Here's my solution for that dilemma - replaceable soft jaw pliers.

First I took apart a standard slip joint plier and ground the jaws back. I wasn't too concerned with the precise angle, but I did make sure to get each jaw nice and flat:

The jaws are pretty tough stuff, and I broke one end mill before I finished up slotting both sides on the mill:

I drilled each jaw for clearance holes for 4-40 screws, and then I tried combinations of gage blocks in the jaws until I got a nice tight parallel grip on them:

That gave me a good measurement of the space between the jaws when they were parallel. My reasoning was that it didn't matter exactly what the dimension was, as long as I knew the measurement. It would have been a daunting task (for me, at least) to have machined the jaws to a precise measurement.

I milled up some mild steel into a T-shape, where the upright part had the same dimension as the slots in the jaws, and the top part had exactly half the measurement of the measured space between the jaws.

I cut the T into sections to be the replaceable jaws.

I made up a pair of aluminum blocks to hold the jaws in the milling vise, pressed the jaws together, drilled and reamed a 1/8" hole right in the center between them:

My current bunch of little screws are threaded to 5-40 - nominally 1/8" O.D.

Gripping the soft jaws in the pliers, I drilled through them for retaining screws:

Here's a shot of the pieces:

Because I wanted to grip the 1/8 threaded portion tightly, I filed the face of the jaws so they wouldn't touch as I gripped the screw.

Here's the result - a solid grip on my 1/8" diameter 5-40 thumbscrew, ready to meet the buffer:

And I have extra jaws that I can drill, ream and set up for whatever diameter comes next.