Trim Ring Jig

I often need to open the inside diameter of trim rings from 3/4" to 7/8" diameter. It's easy when working with a trim ring billet - you just bore them before you part them off. But if you need to modify some .015" metal rings or thin fiber rings, it gets trickier. I made a simple internally threaded press that will clamp a batch of rings together & support them so they are more easily machined.

This is the clamp with an assortment of .015" thick nickel-silver & brass rings that I want to open up to 7/8". The jig has a pocket at its base that is 1 3/8 diameter to locate the rings. The bottom face is undercut so the sharp corners of the trim rings aren't a concern. I will stack the metal rings between the two phenolic rings which add solid support to prevent the metal from bending over, insuring a clean cut.

The first phenolic ring has been installed, followed by the metal rings. The last phenolic ring will be installed next, then the clamp itself will be screwed in, making everything a virtually solid ring, easily bored.

The assembled clamp will then be taken to the lathe for machining. The white Delrin clamp fits inside my 3 jaw chuck nicely so I can clamp firmly on the blue nylon.

You can see the metal rings accurately lined up, ready to be bored.

As you can see, the blue body is solidly gripped and the Delrin clamp does not interfere in any way. In this picture, the rings have been bored to the desired size. A telescoping gage makes it easier to check the size. The rings come out so cleanly cut, they do not even need to be burred.

I do not offer these for sale but anyone with basic lathe skills should be able to crank one out in an hour or two. I also have a sleeve that fits in here that allows me to work on smaller rings.