# US threads to Imperial



## max corrigan (Oct 13, 2008)

Is there a rule of thumb index for translating american thread to BA or any relating imperial threads etc. i have seen one posting, translating this the other way round ie imperial to american which would be ok, but since then i can't find it, i have only found imperial to metric, US to metric etc
i am going to attempt one of the steam engine plans on this website and the thread sizes are all US and put down as 6-40 or something like that! which does'nt give an indication of the dia, or am i missing the patently obvious here!! 
Regards Max..............


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## Mainer (Oct 13, 2008)

I generally convert like this:

8 BA 2-64
7 BA 3-56
6 BA 4-48
5 BA 5-44
4 BA 6-40
3 BA 8-36
2 BA 10-32

Diameter of machine screws can be calculated by:

D = 0.013*n + 0.060

For example, a #5 screw's diameter is 0.013*5 + 0.60, or 0.085 + 0.060, or 0.125".

There's a coarse thread series and a fine thread series. Most of those I listed are from the fine thread series, as I think they look better on a model. The coarse thread series would be 2-56, 3-48, 4-40, 5-40, 6-32, 8-32, 10-24. (In case it isn't obvious, the number after the dash is the tpi.)
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## Bluechip (Oct 13, 2008)

Hi troops

Would this help ??

http://www.watchman.dsl.pipex.com/thread.html

Even some 'Watchy' type threads to [ possibly ] amuse Kludge. 

Dave


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## mklotz (Oct 13, 2008)

The attached chart relates BA to the closest American sizes. HTH. 

View attachment THREADBA.TXT


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## max corrigan (Oct 13, 2008)

Thanks Marv, Dave, and Mainer,have got the chart downloaded, am now a happy bunny  would like to have done "Bogs Little Engine" but thats in metric! although the last few years of my life i worked in metric, my brain still thinks in imperial, albeit frations! and the old myford lathe, tools, mill, end mills, etc. are all imperial, and its too much hassle to keep converting everything, so a US steam engine it will be!
Regards Max.............


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