A little embarrassed, can't read this outside mic....

Micrometers that read in inches commonly are based on a 40 threads per inch spindle.
1/40 = 0.025 thread pitch. That is why one turn of the barrel is 0.025. I have some mikes with the vernier for reading 10ths and some without. I can read either with repeatability and accuracy using interpolation, just as other posters have done by reading your photos..
 
mmcmdl said:
.1525 . Have you been celebrating the holiday today ? :big grin::beer bottles:
Click to expand...
One wonders, there must be literally millions of micrometers out there that do not have the vernier scale, only one mike that I have does have it, an 0-1, that out of mikes up to 12". My mother's uncle who apprenticed at Brown & Sharpe before WW-1 gave it to me, go figure, it was a Starrett.
 
I guess I missed the Ninja edit. :)
 
I learned how to interpolate between the marks in slide rule class in high school. When I got to college, the first physics lab was how to read a micrometer. It was an analog world back then and you had to know how to interpolate to get the extra precision. I have a B & S micrometer that has a vernier for tenths but I rarely use it. Every time I have checked my interpolation, it has matched the vernier. It should be stated that there is no additional precision gained by adding the vernier. The precision is built into the screw. The vernier just makes it easier to read.

Regarding interpolation, to gain experience by first just looking at the position between the marks. If it's halfway it' .0005" If it's nearer the low side than the high side, it's .0004" or less. Nearer the high side, it's .0006" or greater. If it looks like it's about halfway between the lower mark and the middle, it's either .0002" or .0003". Just a shade past the lower mark, call it .0001". If you have a digital mike or a set of gage blocks, you can practice with some known quantities. It won't take long until it is second nature.
 
What is your tolerance on what you are measuring. If it's plus minus one thousand and you are looking for .025, you are more than good enough.
 
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