Bright steel

[JasonBModerator @jasonb]

M3 x 0.6 is probably as good metric version of 1/8 x 40 (Whit & ME) and #5-40 UNC as you will get without the pitch going into too many decimal places.

[Anonymous]

Posted by JasonB on 04/05/2023 18:19:09:

M3 x 0.6 is probably as good metric version of 1/8 x 40 (Whit & ME) and #5-40 UNC….

More likely that the French metric system used 3×0.6 as standard until sometime after WW2, and was presumably copied by Japanese industry. For thread diameters below 3mm the French system used thread angles of either 50° or 60°.

I came across 3×0.6 when making replacement parts for a guitar for a friend of a friend. I only identified the thread when I noticed that the guitar was made in Japan.

Andrew

[Dave WoottonParticipant @davewootton]

Years ago at work we had some steel to machine clamp bars to hold contacts in some HV switchgear, I can't remember the grade or spec but we called it " Horribillium" it would machine and drill ok but was the very devil to tap threads in. The solution was to use either White Wizard or Blue Wizard machine taps with rocol RTD compund, again can't remember which, but they would work and cut a good thread, but didn't last long before blunting. I don't know if wizard taps are still available but assume some equivalent is, but do remember being told they were very expensive at the time and were originally purchased for tapping Aluminium Bronze which can also also be horrible to tap.

Probably cheaper and easier to buy some more steel of a known spec from a reputable supplier. my home made toolmakers clamps are ordinary ms and have lasted about fifty years so far!

Good Luck

Dave

[RobinParticipant @robin]

I had a problem recently in cold rolled. The thread was hard to cut so I did frequent reversals to stop it jamming but all to no avail. Ended up having to push hard to back it out and it chose to break

Presto taper tap with a sulphurised cutting oil IIRC

[mark costello 1Participant @markcostello1]

One thing that I have found to work extremely well in 304SS is I tried pure Molly Dee in engine assembly lube. It worked very well. Almost like tapping regular steel. You know how when hand tapping something hard to tap and You stop and bread the chip and it starts cutting again with a little crack? With the assembly lube there is no little crack and You can just continue on. Suprised Me.

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