What are these things!?

[Nevermore11]

Not sure if these are even machinist related but they are a mystery to me!

Anyone have any clue?




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[Terrywerm]

My first reaction was that they are expanding mandrels, but upon taking a closer look, I am not so sure. The outer copper sleeve is something that I've not seen before. Of course, there is nobody saying that I've seen it all either, and least of all, me! I am afraid that I will need to defer to someone else that may have a better idea than me.

 

[Nevermore11]

Thanks for the reply! I just did some quick research based on your suggestion and I think you are right on!!

I can't really tell but I think the shafts may be non-sparking beryllium, which if that's the case these must have had a specific application somewhere


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[682bear]

I think they are used along with a polishing compound to polish the inside of holes.

I have used a couple of similar tools (although much smaller diameter) in the past polishing ejector pin holes in plastic injection molds.

-Bear

 

[Bob Korves]

Not sure if these are even machinist related but they are a mystery to me!

Anyone have any clue?

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Those are copper laps. They are used to finish holes to an accurate size using abrasive paste.

 

[Terrywerm]

So last night I am laying in bed and my thoughts drifted to those things, and sure enough, it dawned on me that they were laps. I've not seen any in a very long time, and the ones I saw were brass instead of copper, and looked a bit different than the ones that you have. I don't have any myself and have never used one either. What really threw me was the knurled pattern showing on one of those in the photo.

This morning I jumped online to verify my thoughts and found these as an example at MSC: https://www.mscdirect.com/product/details/05070487 They have other sizes and types available as well.

My next stop was this thread to post what I found, but I see that Bob beat me to the correct answer.

 

[kd4gij]

+1 they are lapping hones

 

[markba633csi]

Probably beryllium copper which is rare and expensive these days, very tough material and non-sparking- I have a drift around here somewhere made of it
Mark S.

 

[Bob Korves]

They are made of relatively soft copper so the abrasive can work its way into the copper, and then lap the steel, not the copper.

 

[Billh50]

They are laps for polishing a hole to size. Usually for something that needs a close slip fit.