Machinist/mechanics-Need your help with this tool.

[VaTom]

Years ago I inherited some tools from a family member. He was a mechanic for Chrysler back in the 1950s and 1960s. Many of them were service awards. I know this is a micrometer but I don’t know how to read it. I have wanted to use it to measure thickness but don’t know how to read the numbers.
Thanks for any help.

 

[ralph7]

You tube is your friend!

 

[Tom S.]

That mic reads in thousands of an inch. One one-thousandth is written as .001 and one hundred one-thousandths is written as .100

The part that turns, the thimble, is marked 0 to 25. Each mark on the barrel (the part that doesn't turn) equals .025 thousands. So if you start out with the mic closed, the 0 on the thimble should match up with the 0 on the barrel, and no barrel marks will be seen. As you open the mic up, the value on the thimble that lines up with the horizontal line on the barrel, plus how ever marks show on the barrel is your reading. So if the mic showed 15 marks on the barrel and "0" on the thimble piece, that would equal 15x.025 or .375

It's easier if you remember that the numbered marks on the barrel equal .100, so 3 = .300, and so on. then add the number marks showing after that number, so in the example above, you would 3 plus 3 more marks on the barrel, and since each mark equals .025, the total figure is .375.

Now for the thimble. If the thimble piece is not at zero according to the horizontal line on the barrel, then whatever value does line up with the line is added to measurement. In the example above, if the thimble said 5 instead of 0, then the resulting measurement would now be .380 (.375 plus .005). It is most important that you remember to only count lines on the barrel that are not covered. Another example, if the barrel shows 6 plus 2 marks and the thimble lines up with 20 on the vertical line, the measurement is .600 plus .050 plus .020, or .670 It is important to just tighten the thimble until it stops. Over tightening will give false measurements and could result in the mic needing recalibrating - which the mic in the photo looks in need of having done.

Easy-peasy....

Or watch Youtube.

On "tenth" mics, (stands for one- ten thousandths of an inch) which the pictured mic is not, you can measure down to .0001 of an inch. The typical human hair is around .003 for comparison, so that would equal 30 'tenth's measurements.


BTW: Guys in the shop jokingly referred to them as "calibrated c-clamps".

 

[Papa Lee]

Technically speaking that is a Micrometer Caliper (meaning that it is a caliper that uses a micrometer method of measurement) which over the years has been shortened to simply "Mic". Tom S. gave a good explanation of how to get a measurement of thickness or diameter with it.

 

[Protocall_Design]

Tom gives a good explanation, but I'm wondering if maybe 3 plus 3 marks would be .375 instead of .385?

 

[rockquarry]

Once you become familiar with use through practice, they're almost as easy to read as a ruler and far better than a digital micrometer.

 

[deadin]

While you are at it with "Tricks of the trade"
What is the best method to measure the diameter if a odd number of groove barrel or slug?

 

[Thaddeus Beauregard]

This video does a good job of explaining how to read mics:

 

[Smoke]

First, let me say that I apparently don't know how to use micrometer. The reason I say that is because when I read this discussion I realized that I couldn't explain it without a micrometer in my hands.and I've always been taught that if you can't teach somebody else how to do it you don't know how to do it.


So this is an artillery micrometer. It is used for reading the angle of the tube. It can also be used for reading the cant of the gun.

The very first machine shop I ever worked in one of the questions they asked me during the interview was "Do you know how to read micrometer?"

Of course they meant this

And I didn't know what they were talking about but I said yes because I knew how to read the one above. I got the job

 

[Protocall_Design]

While you are at it with "Tricks of the trade"
What is the best method to measure the diameter if a odd number of groove barrel or slug?

There are what is called V anvil mikes for measuring 3 and 5 flute cutting tools, such as reamers, end mills, etc. The 5 flute one works for measuring S&W barrel slugs.

0.2-1" 108 Degree 5 Flutes Measured V-Anvil Micrometer

www.shars.com

 

[sophie]

What am I missing on this thread?
The picture appears to be an older 0 to 1” micrometer.

 

[Tom S.]

Tom gives a good explanation, but I'm wondering if maybe 3 plus 3 marks would be .375 instead of .385?

Isn't that what I said???? Well it was after I edited it!!!

 

[Protocall_Design]

Oh, right. What was I thinking?

 

[Oldengineer]

How does this one work?

 

[oldbrownhat]

What am I missing on this thread?
The picture appears to be an older 0 to 1” micrometer.

Also curious as to the brand. If older I would assume perhaps Starrett or Browne & Sharpe? All I can see from the pic (once I lightened it up a bit) is "MTSC Award" which might refer to the original owner.


I picked up a nice old Starrett 0-1 several years ago for about $35 in a secondhand shop . (Long before the quality started to go downhill) I prefer a digital but this was so nice I couldn't resist.

 

[deadin]

Holds things steady while you measure with the other one?

 

[nedlate]

How does this one work?

Nice Vise!!