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What's Wrong with this Picture??? MSC 2-1/2" Expanding Arbor

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--- Quote from: vtsteam on April 11, 2022, 08:52:39 AM ---Anyway, what to do......

Well, notice the following ad, also found on Ebay. See any difference? And these are smaller -- 1-1/2" 1-3/4" and 2"...

--- End quote ---

I think you're going to have to try machining that groove!

Right Russel!

So, how deep should we relieve this thing? Well, looks like the properly made set has a 1-1/2" diameter version, and it was found necessary there to add relief -- so checking that photo and enlarging it, it appears to me that the relief cut is a little shallower than the chucking stub. And checking their specs in the advert, that stub is 1" dia. So the relief cut must be less than 1-1/2" dia and more than 1" dia in depth.

I make that out to be 1-1/4".  :smart:

Okay out with the parting tool.......

I think your expectation of 0.005" expansion is a little ambitious. This is approximately the same figure used as an OK measurement for 5C collets. Compare and contrast a 5C collet to what you have and perhaps reconsider.

This ain't a 5C collet. I've made these before.

Also what 5C collet would work with inch thick walls? And an R8 closes down ten times what a 5C does. Chalk and cheese.

Here, good explanations and types of shop built expansion arbors illustrated. Note the relief cut on even a small diameter aluminum version, and the grip range.

Turning a relief slot. I went in a half inch -- the example arbors would have meant going in 5/8", but already I have 10 thou expansion now with reasonable hand tightening of the wrench instead of 5 thou wrestling a cheater pipe extension on the wrench to get it.

Ten thou is a reasonable tightening range, since a typical tube part requires about 5 thou clearance to slip onto the arbor before tightening. Another 5 thou of range gives a good enough grip for what I need

The original supplied 8mm Allen wrench gave no expansion at all prior to modifications and before the bigger handle wrench was made.


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