Material for Collet Holder

[Anonymous]

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[Neil LickfoldParticipant @neillickfold44316]

Posted by Dalboy on 01/06/2023 21:00:45:

I wonder how hard the shaft is on one of THESE as it is only just over size. Could it be brought down to size

They are quite hard. The ones that I have are around 58Rc, a lot harder than I thought they should be. On one of the ones for an ER11 that I shortened , 16mm diameter shank is a very good Ø16.00 , was I think a case hardened material, as it was hard and soft then hard around the centre hole. Unless there is a form of induction hardening that will harden on the outer as well as the inner and then leave the core soft.

To take it down to 5/8 diameter, you will have to Hard turn the adapter , which is not as bad as it is made out to be.

Just need a sharp geometry carbide insert, like these for an example, Kyocera CCGT060202MP-CK- grade PR1425, or PR1225 . It will work with a light dab of cutting oil, will smoke of course, and will cut the shaft down in a couple of passes. Just make sure that the top slide is locked so no movement, and the the gibs on your lathe is not too loose. If you are using a lathe lighter than a Myford S7, like a Sherline or Taig type lathe, then I would do it in 3 passes. I use these Kyocera inserts at my work for hard turning, and for home when cutting the diameters of bearings. You will want the lathe to be doing about 500 rpm, no more than 600 rpm, and try to feed at a rate of 0.05mm/rev, but anywhere from 0.02mm/rev to 0.1mm/rev will still work fine.

If when you start hard cutting, and it chatters, then just go to slower rpm. Make sure you are using a support on the end, like a tailstock, and shorten the length, after you have cut down the section that needs to be Ø5/8 or what ever is actually needed.

The hard turning, works on my home made Taig type lathe that I have put together.

Neil

[A SmithParticipant @asmith78105]

I made an ER 25 Collet holder EN1A some years ago, it proved perfectly satisfactory. I'd avoid cast iron for the same reasons everyone else has given. No stupid questions, you know the rest…….

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