Micrometer adjustment

J

JoshEarl

Joined
Sep 30, 2007
Messages
197
I have one of those intro-level micrometers from Jantz. The brand is "General." I can't figure out how to adjust it.

It was off by almost .001, so I tried to adjust it with the two-ended C-spanner wrench that came with it. I can't get the barrel to turn at all. It might be set in place permanently. When I try to turn the thimble, it seems to just open and close the micrometer. If I apply a lot of force, I can change the reading. Now it's off by .002" in the other direction. :mad::thumbdn:

All the directions I'm finding online make the process look really straightforward. What's up with this one?

Josh
 
I've found that most mics are very tight and you have to hold the "C" frame of the mic in a padded vice ane use the spanner wrench with quite a bit of leverage. Hope this helps...
 
Hmmm. I'll have to give that a try.

Can you adjust both ways, or should I go all the way around again, if that makes sense... It seems like if I turn it in the direction that would normally open the micrometer, the lock slips.

Josh
 
It turns both ways. I put a shop towel over the vice jaws and clamp the mics in with a minium of pressure. I have a 6" piece of 1/8" pipe that I put over the end of the spanner to give me more leverage and control. It is much easier to make very small adjustments with the pipe on the spanner...
 
WhitleyStu said:
It turns both ways. I put a shop towel over the vice jaws and clamp the mics in with a minium of pressure. I have a 6" piece of 1/8" pipe that I put over the end of the spanner to give me more leverage and control. It is much easier to make very small adjustments with the pipe on the spanner...
Click to expand...

When I try to turn from the notch on the rachet thimble, it unscrews. I've taken this thing completely apart and I can't see how it would adjust. Grrr.

Josh
 
I think you are using the wrong hole. There is a hole on the round graduated stationary part of the mic just to the right of the "C" frame (the hole may be on the top, bottom, or back). The hole in the button on the end of the turnable part gives you access to the ratchet (not where you want to be).
 
I like the digital readout ones. Just turn it on and push the "zero" button. Works everytime. I know this isn't much help.

But, like they've said, precision measuring equipment is very difficult to get adjusted with the small wrench supplied. They're tight so that they aren't loosening up all the time. Good luck.
 
WhitleyStu said:
I think you are using the wrong hole. There is a hole on the round graduated stationary part of the mic just to the right of the "C" frame (the hole may be on the top, bottom, or back). The hole in the button on the end of the turnable part gives you access to the ratchet (not where you want to be).
Click to expand...

I tried to turn it with the hole near the C frame, and it wouldn't budge. I'll have to try it again tomorrow in the vise. I was able to exert enough pressure to dent the barrel slightly with no sign that it was going to move.

Thanks for the help so far... :)

Josh
 
Thanks for all the help, guys. It turns out there was a small set screw on the barrel. When I removed that and put the mic in my vise, I was able to break the barrel free of whatever was preventing it from turning. (Maybe just some stray paint in the joint...) After that it turned a little easier, and I was able to get it adjusted. I had tried turning it with the set screw out before, but not with the mic in the vise.

My mic is now reading properly, although it's a little beat up from my efforts... :)

Josh
 
Setting a Mic is a precision job. I used to work in the gage room for a machinist company. It was 70deg all year round and mics had to sit in the room for at least 2 days before they were adjusted. Temperature and humidity will affect the final readout when adjusting it.
 
striper28 said:
Setting a Mic is a precision job. I used to work in the gage room for a machinist company. It was 70deg all year round and mics had to sit in the room for at least 2 days before they were adjusted. Temperature and humidity will affect the final readout when adjusting it.
Click to expand...

I encountered similar stories in my web searches... I'm sure mine is worlds away from perfect, but I really just need it to be in the same universe as accurate. :D

Josh
 
If we're talking a 0-1" mic. the temperature has no bearing on whether or not it is set right at zero... 0=0... On All other mics, it does make a difference, but not a 0-1".
 
howiesatwork said:
If we're talking a 0-1" mic. the temperature has no bearing on whether or not it is set right at zero... 0=0... On All other mics, it does make a difference, but not a 0-1".
Click to expand...

This is true. And adjusting the others at 70 degrees F. isn't what is most important. What is most important is that the mic and the master used to set it are normalized to the same temperature. Around 70 degrees is an industry standard, but the same temp is vital for accuracy.
 
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