Threads for screwed shank End Mills and Slot Drills

[Jerry WrayParticipant @jerrywray14030]

I need to clean-up some threads in screwed shank collets and end mills.

I believe these threads are Whitworth form of 20 tpi with diameters equal to the shank, either imperial or metric THe tread form and pitch are the same for both.

Harold Hall's Metalworkers Data Book confirms these dimensions.

Can some one advise me where I can obtain taps and dies to these sizes. I have tried the usual sources.

Thanks

Jerry

[Jerry WrayParticipant @jerrywray14030]

Where to obtain taps and dies

[DMBParticipant @dmb]

Tracy Tools?

Edited By DMB on 26/04/2015 15:42:18

[Jerry WrayParticipant @jerrywray14030]

Tracy were my first thought. If I consider for example a 6mm shank 20 tpi is 1.27 mm pitch (25.4/20 ). I don't know if this i sufficiently accurate as a 6mm collet has an internal thread of almost an inch.

Jerry

[BazyleParticipant @bazyle]

Thread chaser perhaps, or even thread file (from Chronos)

[JasonBModerator @jasonb]

Could you not grind up the screwed shank of a blunt cutter to make a "tap" to restore the internal threads and a thread restoring file as Bazyle says for the external threads

[Jerry WrayParticipant @jerrywray14030]

Thanks Bazyle and JasonB,

I have a very worn 6mm shank End Mills which I will try to grind into a (hopefully) suitable form to act as a tap. I also have some files which was my father's which he used to use to cut large Whitworth threads for earth moving machinery. I just need to dig them out, from his toolboxes (not from the earth).

Good job I am now retired.

Jerry

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