This is one of those where I think the answer is obvious, but I'm not certain.

If you need to cut an M12 thread onto a steel bar with a die, do you need bar that is EXACTLY 12mm or slightly bigger or smaller?

Thanks in Advance

Chris

measure a m12 bolt and add 1mm to the outer dia.
adam

Ø12mm bar would be the correct start point I believe. I can check me Zeus book if need be

http://www.sealey-tools.co.uk/instructions/AK3002.PDF
adam

quote:

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Originally posted by nick205
Ø12mm bar would be the correct start point I believe. I can check me Zeus book if need be

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you need 12mm o/d

Andy

Thanks for the replies chaps, it says on that link that the bar should be 0.005" to 0.0010 undersize. What's that in metric? (and the 21st century)

Cheers

Chris

12.0 to 11.9 would be perfect

That is 11.975-11.875 I think. 0.001" = 0.0254mm

[Edited on 29/11/07 by Mansfield]

I've got 12mm exactly, so I should be ok?

Cheers

Chris

You will be fine, use plenty oil and keep it square.

If it it a split die you could open it right up for a first pass and close it to finish size for a second pass if you fancied.

The nominal dimention is indeed the OD of the male thread before its cut.
- With the nomial dimention minus the pitch being a good aproxamation of the ID of the female.

However, there are tables with all of this in. Zeus, etc.


Daniel

quote:

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Originally posted by Mansfield
If it it a split die you could open it right up for a first pass and close it to finish size for a second pass if you fancied.

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quote:

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Originally posted by MikeRJ

quote:

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Originally posted by Mansfield
If it it a split die you could open it right up for a first pass and close it to finish size for a second pass if you fancied.

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Unless it's make from Chinese "high carbon steel" in which case you end up with a special two piece die

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I bought a couple of cheap tap and die bits, utter utter crap. You know when you have to file off the burrs on your tap, that something is not right. Plus the thread it cuts could be described as a slightly rippled slip fit for the bolt.

I have a bookmark for this place: http://www.tapdie.com/ which may have come from another post on here, never used them, but intend to when I need taps + dies again. Looks like the real deal at reasonable prices.

I know this wasn't a "where do I get tools" thread but I came over all helpful

Lots of useful info on here, including metric threads.

http://www.engineersedge.com/Design_Data.shtml