Fixturing for machining teflon rings

After some rumination, I think the original sequence of operations was

1. Hold the work blank by the outside scrap, finish the ID
2. Center the work by the ID, hold it by the face and finish the OD.

Initially I didn't like that sequence, because it required two accurate operations of which only the second mattered, doubling the risk of error.

Looking at the tooling required for my preferred sequence, the original method looks a bit simpler for only three parts. The idea of using pipe caps for mandrels never crossed my mind and seems a good idea. They can be run between centers, making them reproducible.

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The wooden stub mandrel automatically solves the centering problem as long as it's a close fit in all the rings, which you can ensure by boring the ring blanks as a stack. My preference is oak, such as firewood, with the grain along the lathe spindle axis which lets the lathe bit cut uniformly all around; the grind for metal isn't ideal for wood. Alternately you could screw two blocks of pine 2x4 together and chuck it in the 4-jaw.

I totally agree with the comments there regarding pros and cons of 5C and ER collets as I have both and have encountered some of those limitations.

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What do you think of this, which puts ER collets on a 5C indexer?

That looks like it might come in handy as I have a 5C indexer and a full set of ER40 metric collets, my 5C collet set only contains some common metric and inch round sizes acquired as needed or some common sizes to have on hand just in case. I have a 5C 3 jaw self centring chuck for dealing with hex stock. The ER40 full set was bought later and now sees more use than the 5C and I have an ER40 square and hex block for 3,4, and 6 but I can see the temptation to treat myself to one of those in time for Christmas. Thanks for the heads up.

Here's a YouTube video of an alternative holding scheme for thin rings:

It relies on a three jaw chuck for clamping a simple right circular cylinder collet with a single split. Wish I'd seen it sooner.

It's not clear I could have used it, as my three jaw chuck didn't come with reversible jaws, but I'm still slightly embarrassed that nothing like it ever crossed my mind.

Thanks for reading,

bob prohaska