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Caliper Calibration on a Shoestring

E

El Capten

#1
I just started a position at a new company and need to set up a gage calibration program - nothing exists right now, and there is no real budget for it this year. I have purchased a set of Gage blocks and am able to calibrated the caliper jaws to check outside dimensions from zero to 6 inches.

I am looking for ideas on how to calibrate the calipers' inside reading blades myself. I dont have the option of buying an expensive check device at this time, and would rather not have to send the calipers out for outside calibration work.
Thanks
 
S

smkeilman

#2
If you're doing a full scale calibration on the outside jaws (0, 2, 4, and 6 in. for example) and your caliper has only one scale (such as a digital or dial caliper), then only a single point check is needed to calibrate the inside jaws and depth rod (if applicable). You can use a master ring gage to do this, or, if you have square gage blocks, you can also purchase end blocks.

A .500" XX Ring gage has a tolerance of +/- 15 millionths and will run you about $100. You'll need to send this out for calibration periodically.

You should check the ring at the edge of the jaws and near the base to check the parallelism of the jaws.

If the caliper has separate scales for inside and outside measurement, then you will need to do a full scale check.
 
B

bkelchner1957

#3
I use 3 ring gages, which are then calibrated with the gage blocks by an outside calibration lab annually. ID measurement frequently goes out when calipers are dropped. Also tip wear with use. I have seen depth rod wear also. Can check OD, Step and Depth rod with Gage blocks, ID needs Ring gages.
 

JLyt207

Involved In Discussions
#4
If you're doing a full scale calibration on the outside jaws (0, 2, 4, and 6 in. for example) and your caliper has only one scale (such as a digital or dial caliper), then only a single point check is needed to calibrate the inside jaws and depth rod (if applicable). You can use a master ring gage to do this, or, if you have square gage blocks, you can also purchase end blocks.

A .500" XX Ring gage has a tolerance of +/- 15 millionths and will run you about $100. You'll need to send this out for calibration periodically.

You should check the ring at the edge of the jaws and near the base to check the parallelism of the jaws.

If the caliper has separate scales for inside and outside measurement, then you will need to do a full scale check.
I agree that a ring gage is what you need. I would be worried if your company balks at $100. That said, if you don't have square block set with end blocks you can mimic it with 3 gage blocks in a row rung together. The two end blocks slightly off the edge of the center block and use those exposed faces. Now I would only do that for calipers and only until you are allowed to buy a ring gage.
 
P

PaulJSmith

#5
... if you don't have square block set with end blocks you can mimic it with 3 gage blocks in a row rung together. The two end blocks slightly off the edge of the center block and use those exposed faces. Now I would only do that for calipers and only until you are allowed to buy a ring gage.
Perhaps as a casual check, but not sure I'd want to try to justify that for an actual calibration.
 
#6
Y porque no ? Unless you're using calipers beyond their intended accuracy, precision and reliability it should do the job. They're the pair of pliers of precision measurement - good for everything and not particularly great for anything.
 

JLyt207

Involved In Discussions
#7
I agree. It is quick and dirty and more of a sanity check than a calibration. That is why I tried to surround it with caveats. I did forget to mention you still need to hold the blocks together mechanically. It is merely better than not checking the inside jaws at all. But I wouldn't use calipers for anything tight. I can't think when we use them for less than +/-.015.
 

R. Webb

Involved In Discussions
#10
To calibrate the inside reading blades I use a micrometer that I have calibrated with blocks. Many of the calipers I calibrate are 12 inch variety and the inside blades have visible and distinguishable flat spot. This makes using a ring gauge a little problematic. The flats on the micrometer anvils work just fine. I set the micrometer to whatever is convenient at the time and measure the distance with the caliper.
 
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