I have never calibrated parallel bars or plug gauges (Go/Nogo). I'm looking for information regarding these items ie technique to calibrate, requirements and standards.
The way that I've calibrated parallel bars is to use a calibrated surface plate, a high accuracy indicator, and an indicator stand that you can use to sweep the bars with. Below is a method that I used to use. I think it works well
EQUIPMENT
_ Height stand with dial indicator
_ Surface plate
_ Deburring stone
5. PROCEDURE
5.1. Verify that the identification markings on the bars are proper and distinct.
5.2. Clean the exterior surfaces of the bars as required using cleaning solvent.
5.3. Visually examine the bars for obvious damage, abuse, or wear that would make calibration impossible. If applicable, discontinue procedure and reject, and record findings
5.4. Check for flatness by placing each bar on a surface plate and pressing the bar against the surface plate alternately at each end and along each side.
5.5. If rocking is observed, reject
5.6. Using a height stand with a dial indicator, indicate across each parallel near each end and at midpoint.
5.7. Record the greatest deviation of each parallel with relation to 6 inch length, and variation in the height of the parallels
5.8. Rotate the parallels to bring up opposite faces and repeat paragraphs 5.6. and 5.7.
5.9. Rotate parallels 90 degrees and repeat paragraphs 5.6. and 5.7.
5.10. Flatness, parallelism, and vertical variations between like dimensions shall be within .0002 inch per 6 inches of length.
As for plug gages, you'd need a bench micrometer that is better than your TI. Standardize your micrometer to a good gage block close to the size you're measuring. Make sure the anvils of the mic are clean as well as the gage itself. Hope that helps!
Using a standard bench mic, such as a Starrett 777, isn't an adequate substitute?
Previous information helps, thanks.
The Starrett 777 is good enough depending on the class of the TI. If you're doing zz or maybe even a z class pin, that can be ok but if you were doing x or higher you may want to look into a super micrometer like a P & W. I used to use a Trimos brand one too. It all depends on high tight you want your TURs.