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I am a little surprised that the thread chart doesn't have information for cutting 13 threads per inch. Am I missing something?

Mike
 
Reeltor said:
I am a little surprised that the thread chart doesn't have information for cutting 13 threads per inch. Am I missing something?

Mike
Click to expand...
Simple, It is a british lathe and no standard british thread has 13 TPI. Only american threads use 13 TPI. As to why, no one has been able to tell me.
 
Hello bob, i know about the 120 and 127, I use a Colchester bantam quite often and endlessly switching between metric and imperial!
Is 13 tpi quite a common thread over there then?
 
Pmma-Granville said:
Hello bob, i know about the 120 and 127, I use a Colchester bantam quite often and endlessly switching between metric and imperial!
Is 13 tpi quite a common thread over there then?
Click to expand...


Yes 13 TPI is the standard pitch for 1/2" UNC in USA and Canada and all their territories, Its also common where american made motor vehicles are widely used. All other sizes use the same pitch as BSW. 1/2"is the stand alone different one and nobody seems to know why, although I suspect it came about during WW2 Even though the pitch is the same on all other sizes the thread form is quite different.

Here in Aus we have traditionally used a mixture of both British and American specs in all things. Although we are now officially metric, so now we have three standards. But even back in the 60's when I was doing my apprenticeship we had to learn all three because we had a mixture of machinery of all types from all over the world.
 
Thanks for the info! That's quite interesting.
Iv not long finished my apprenticeship, everything iv done has been metric, now I'm getting myself used to imperial too. Hopefully it won't be too much of pain switching between the 2 with work in metric and home in imperial!
 
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