A Universal Expanding Ring Mandrel for the Small Lathe

By Nick Carter

The other week a friend came by the shop for some jewelry related lathe help. She was using a ring holder meant for benchwork (GRS Benchmate) to chuck her rings, both waxes and metal) for turning. While her holder worked, I thought I could come up with something better. Based on the Taig #1132 Blank Arbor, the mandrel shown here could be made with a straight shank as well, for mounting on a variety of lathes. As shown it will work on the Taig lathe, and if you turn down the end of the blank arbor for about 1/8", on the Sherline lathe as well. If you want to make it with a straight shank, you should chuck up some 1/2" rod in your lathe chuck, turn the end down to 1/4" dia for about 1" to 1-1/2", then chuck that 1/4" shank in a 1/4" collet on your lathe (Taig, Sherline and watchmakers collets all are available in 1/4" internal diameter)

A note on materials, the 1132 is made from free machining steel, I also made the two conical washers of free machining steel. You could use any metal you wanted for the conical washers. The expanding arbor is made of Delrin, but again you could use any plastic, metal or even a hard urethane rubber.

Because of all the pictures I have divided this article into two parts. Part 2 is here.

The Blank arbor. The 30 deg taper is mostly for tool clearance, it is not critical. Try and hold the diameter of the .3125 spigot to about +0/-.001 if you can. Hold the length of the spigot to about +/-.020. Nothing is that critical. The end of the 1132 is already tapped for the Taig spindle.

Make 2 of the conical washers. Try and get the angle as exact as you can. During and after turning break (deburr) all the sharp edges. It should be a slip fit on the mandrel spigot.

The expanding arbor hole should be a good clearance fit on the spigot, the hole diameter isn't critical as the conical countersinks center the arbor.

Make the conical countersink to fit whatever countersink you have one hand, there is no reason for it to be 60 degrees instead of 82 or 90 or whatever you have on hand.


The 1132 blank arbor mounted on the lathe
Drilling a 3/16" cross hole in the arbor, for a spanner to tighten and loosen. You could also mill flats for a wrench if you wanted. I did this on the drill press but it could be done on the lathe.
Starting to turn the spigot.
The spigot finished.
Setting the compound.
Turning the conical relief on the blank arbor.
Center drill the spigot.
Drill the spigot #21 for a #10-32 tap, as deep as you can (I drilled an inch deep)
Tapping the end of the spigot. I used a "gun" tap which is preferable for a through hole. The Taig tailstock ram slides so I was able to chuck up the tap and turn the spindle with a wrench. The tailstock kept the tap aligned.
Closeup of the tapping.
The finished arbor.

Continue with Part 2

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