I've got an old screw pitch gauge that I inherited. There's no mfr's name marked on it, just "Number 137".
the individual leaves are marked with two numbers each, but these numbers are not reciprocals. The first number is always a small integer which I presume is threads-per-inch.
the second number is always a decimal.
All the leaves are of equal thickness, so they are not thickness calibrations as in a feeler gauge.
Any idea what the second set of numbers are?
Probably metric (in millimeters pitch)
Don
Depth of thread?
=-=-=-=-=-=-=-=-= Rob Skinner La Habra, California
Probably the depth of the thread--handy to know if you're cutting threads on a lathe. If you post a few examples it would be easy to verify this.
Ned Simmons
Depends upon whether it's metric or imperial. The most likely is that the first is TPI, as you say. The second is probably the bolt diameter in a thread series. The most likely is BSW.
John
The second set of numbers, decimals, is the double depth of the thread pitch .
Harold
treat the first number as TPI I have added witworth form thread depth in inches..... doubleing it gives the second number.
N.B. unified thread depth is diferent, at 40 tpi for exampe it's 0.015336.
Hope this helps
-- Jonathan
Barnes's theorem; for every foolproof device there is a fool greater than the proof.
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