Machine Screws (inc. archaic sizes)


H-M Supporter Gold Member
Feb 13, 2017
As requested:

It must be understood that most of my projects involve small scale models. 3.5mm to the foot. A rather odd scaling, that. 1 inch=0.011", approximately. Of the listed sizes, I keep taps as small as 3/0-120 in imperial, and 1.0mm metric. Dies are used less often and only size to 2/0-90. Metric taps and "screw plates" run from 1.0mm(0.040") and up.

Of the archaic sizes I keep, many dies that I never (yet) use. Mostly as a curiosity, if truth be known. There are many archaic threads referred to as "special". I have never run across them but you never know working with old machines. There are many "holes" in the chart. Mostly, the conversion from one to the other involves a calculator. My eyes just aren't up to it, I get sleepy.

Most of the entries come from charts. Some from my memory. Such as 1mm = 0.03937, Imperial machine screws start at 0.060 plus 0.013 for each size. i.e. #2-56 is 0.060+(2x0.013)=0.086 base diameter. The threads are pretty much standard.

The PDF file, if printed as 8.5X11, is quite legible. The JPG is just for show.

Bill Hudson MachScrews.jpg MachScrews.jpg


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