Using a thread micrometer.. where do you get the sizes from?

woodchucker

woodchucker

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When you use a thread micrometer, how do you know what size you should be reading? It's not thread wires, so where do you get your info from?
 
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Machinery Handbook is what I use.
 
How about when you don't have the thread listed?
like #12-20 a special thread
and what do you use... basic pitch diameter?
 
Pitch diameter from the charts is what you want. It should have a range, try for the middle, but anything in the range will work.

Make sure you zero with the anvil you need before measuring if yours is swappable. Try a couple of commercial threads or compare to wires the first few times. Once it clicks they are easy to use, but seem weird at first.
 
ttabbal said:
Pitch diameter from the charts is what you want. It should have a range, try for the middle, but anything in the range will work.

Make sure you zero with the anvil you need before measuring if yours is swappable. Try a couple of commercial threads or compare to wires the first few times. Once it clicks they are easy to use, but seem weird at first.
Click to expand...
thanks, I don't have a micrometer yet, but am looking.. Just figured it might be a good time, since I am doing some special threads.
 
Lacking the goodies, I resort to measuring between 10 or 20 threads with a caliper, and then dividing by 10 or 20.
Add to that the info about the outside diameter. Then it's consult the the charts.
A bit homespun rough-and-ready, I will admit, but so far, I have managed to identify the thread every time. :)
 
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A thread mic reads pitch diameter directly, so PD is all you need.
 
What do you use for a standard to set the mic when anvils are changed. On a regular mic it can be zeroed out with a gauge block of the appropriate size or face to face for a zero to one. How does one do that with a thread mic?
 
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