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Rockwell hardness of collets

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Adam Harris02/07/2021 00:03:34
499 forum posts
26 photos

I have seen an ad for some Chinese SK25 spring collets on Alibaba stating hardness of HRC44-48 and I am curious as to how this compares with a recognized quality brand of similar collets with 6 leaves. Can anyone throw some light on this, and also the range of HRC generally targeted in say manufacturing ER collets?

Edited By Adam Harris on 02/07/2021 00:12:42

Adam Harris02/07/2021 00:21:54
499 forum posts
26 photos

I should mention that the collet material stated by this Chinese maker is 65Mn steel - I have no idea if that is generic or not for SK25 collets...

Michael Gilligan02/07/2021 07:25:12
18921 forum posts
941 photos

I would think that is towards the low end of useful hardness …

but I’m more familiar with watchmaker’s collets, so may be mis-judging.


David Jupp02/07/2021 08:10:16
785 forum posts
17 photos

HRc 44-48 corresponds approximately (you'll get different figures from different sets of tables) to 415-445 Brinell, 440-475 VPN, or a tensile strength of roughly 94-104 Tsi, 1455-1590 MPa. Don't expect these different units to be exactly equivalent - they are just indicative.

Tony Pratt 102/07/2021 08:31:54
1687 forum posts
8 photos

I'm with Michael G, 44-48 Rockwell C is not hard at all. The cynic in me is thinking that these specs are just pie in the shy anyway, a lot of the tooling ads state 'facts' which don't make a lot of sense.


Michael Gilligan02/07/2021 08:48:03
18921 forum posts
941 photos

Sorry it’s off-topic, but here’s a helpful page about Rockwell Hardness of steels: **LINK**


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