Drilling and tapping hard material

[Russ BulleyParticipant @russbulley69715]

I am bushing a small steel casting made in 1929 that is very hard, the steel blunts a HSS drill in an instant. I have broken several taps (by hand) and boring the casting has been a nightmare only solved by using a PCD tipped insert – which then broke! The casting has had a hard life and could have been "work hardened"?

What specialist tap manufacturers are in the UK who can provide specialist taps for very hard materials?

Any tips for tapping, other than winding back regularly and using high quality cutting paste?

Russ

[Russ BulleyParticipant @russbulley69715]

[JasonBModerator @jasonb]

What thread is it, most brand name makers will do a range of material specific taps including ones for tougher steel but not in the more obsolete old threads, OK if you can tap metric or UMC. YG1 for example

If it has work hardened could you anneal it back to a more easily machined state.

Edited By JasonB on 05/08/2020 08:04:15

[Russ BulleyParticipant @russbulley69715]

M6. Great link thanks!

Edited By Russ Bulley on 05/08/2020 10:48:35

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