Brown and Sharpe 30-1 micrometer missing top part

ericc

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Hi. I bought a 2-3" micrometer at a garage sale today. It is a Brown and Sharpe 30-1. It is missing a piece on the top of the barrel. There is a screw hole. Does anyone know what this missing piece is for and what is lost without it. The micrometer was not all that expensive. I compared it with the inside jaws of my harbor freight calipers, and they are different by .002", but that doesn't mean the micrometer is off.
 

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I believe Its the fine feed closer knob (called a ratchet IIRC) which is obvious as to the purpose and it also has something to do with the calibration operation. You loosen the ratchet base with a spanner wrench so that you can pull the larger knob rearward until it clicks and spins freely so that you can reset to the corrected calibration...at least thats what mine was like but im not sure if it was a b&s brand or not.
 
Just a cap missing I think.
Check out this ebay one.

There are lots of them on ebay so many more pictures also.
 
Just a cap missing I think.
Check out this ebay one.
...
There are lots of them on ebay so many more pictures also.

Hi rgray. That's what I'm hoping, that it is just a cap missing. I looked at the link that you posted from eBay. The pictures showing the end of the spindle aren't quite at the right angle. Web searches show various different types of Brown and Sharpe micrometers, including ones with and without the ratchet adjustment. What worries me is that a spanner wrench was in the box and I cannot see where this wrench will fit. Perhaps the spindle is completely retracted and removed, showing a collar which can be adjusted with the spanner wrench. I was hoping that someone recognized this particular model.

As I thought of this, I realize that I don't work to tenths. The only reason I bought this micrometer was that it was cheap. I also had some problems measuring a bore with the harbor freight dial calipers. It was hard to get an accurate and reproducible measurement with them. I had an old 1"-2" thousandths micrometer and a telescoping gauge. I watched a YouTube video and hit the bore dead on! So, I guess that thousandth accuracy is good enough. Besides, the way I was using the micrometer didn't depend on calibration since I was boring to match a spindle. Maybe I should be satisfied with my purchase and just leave it alone. There is a possibility that I may never need the micrometer calibrated.
 
Honestly, in the condition you bought that micrometer alone with many reviews stating how accurate they seem to be I would believe the Harbor freight numbers to be the true value between the difference of the 2 tools.....only because I am pretty sure that cap or ratchet whichever it may be is still part of the system responsible for locking the calibrated adjustment down. Can you pull back on the adjustment dial to see if it will detach from the anvil so that it turns without moving the anvil?
 
You can read the instructions in the ebay listing if you enlarge the picture.
Is that the same wrench yours came with?
Hook end is for rotation the barrel and other end is for adjusting thread free play.

I use a standard to verify a micrometer. Some of mine came with standards.
The calibration thing is if you think the thread is wrong or damaged and I've never gone to the trouble even though I have all the gauge blocks
and could do it. Chances of a problem there are slim for the amount I use my mics.
Now if one had a funny feeling spot or something it would be well worth checking calibration.
I'm also the only one using my micrometers so I know first hand if one got droped or something.

If I understand it right micrometers calibration is "checked". If it passes great. If it fails.....replace it. There are some good youtube videos on it.
 
Doing little reading on the b&s micrometers and the various methods they have used to calibrate the tool would be using spanner wrench in the hole i marked by following these directions...
Screenshot_20191117-165201_Samsung Internet.jpg"Use the included spanner wrench to adjust the barrel of the micrometer to compensate for the amount that it is off. If the measurements you made are bigger than actual, turn it clockwise to bring it closer inwards, and if it is measuring small, turn counter-clockwise until the measurements match up."
 
Thank you rgray and Latinrascalrg1. I didn't think to zoom in on the image in the Ebay advertisement. It is pretty clear. And the missing screw is just a lock screw for the friction thimble. Time to look around for a standard to test the micrometer. I am suspicious that it is fine.
 
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