Screw Thread Micrometer Anvil Calibration

[CaliperJim]

Hi. Do the anvils used in Screw Thread Micrometers, aka Pitch Micrometers, need to be calibrated?

 

[Jen Kirley]

Hello CaliperJim,

These surfaces would be verified, but what is it they are measuring and where does the verfication requirement come from?

 

[Funboi]

Anvils are usually checked with an optical flat. It’s not calibration as such, but a check because their condition will affect the result of the overall calibration.

 

[dwperron]

Hi. Do the anvils used in Screw Thread Micrometers, aka Pitch Micrometers, need to be calibrated?

From what I understand, you calibrate the micrometer itself for linearity.
They sell screw thread micrometer standards so that you can accurately set the zero when you put the thread anvils in the micrometer
Here is a link to an example page:

Mitutoyo

 

[CaliperJim]

Hello CaliperJim,

These surfaces would be verified, but what is it they are measuring and where does the verfication requirement come from?

There is no specific requirement from our customer. I wanted to know if it's standard practice to calibrate the anvils.

 

[dwperron]

There is no specific requirement from our customer. I wanted to know if it's standard practice to calibrate the anvils.

There may be someone who calibrates these, but they don't really qualify as high precision thread gauging tools. The tolerances are usually around ±0.0002", not good enough for thread gauging. And I have read of people getting zero errors in the 0.0025" range. Looks more like a quick and dirty check tool.

 

[Funboi]

My bad. I had a glass of wine and didn’t read the post correctly. The anvils aren’t checked with an optical flat, so throwing them on, say, a shadowgraph to check for wear, or making an impression and checking the form from that could be done.

 

[Enghabashy]

*It's more practical to use Go/No Go thread gauge for mass production , the gauges could be calibrated by 3 wire / horizontal metroscope by competent lab
** Screw Thread Micrometers may have many sets /tips for exchange , each one has gematrical details as standard curve /dimension limits , --therefore the manufacture of each micrometer type should be considered as 1st reference for this issue , the micrometer manufacture is actually calibrate / verify all anvils sets / tips before issuing inspection certificate for his product , the information as tracing of certificates & calibration references could be more useful also for this issues