Sine bar errors

[Paul Jones]

Marv,

Good reminder about the drunken thread errors. I remember reading about this measurement technique when buying used micrometers. In the case of the rack and pinion on my old 6" Mitutoyo dial indicator (bought new in 1970), the rack teeth worn very slightly in a range just before and after the 0.5 position. I used the gage blocks set at 0.2" increments from 0" to 2" to check the measurements. I also checked at 0.5" increments to the 6" capacity but didn'y expect to see errors. Today most dial calipers spec +/- 0.001" accuracy over the 6" length but I had checked this dial indicator when new and several times over the years and it was reading correctly but no longer. I contacted Mitutoyo for spare parts but their response was the model is no longer supported and to buy a used one on eBay and use the parts (not likely). I still use the dial indicator for sentimental reasons but have high-end Mitutoyo digital calipers and micrometers when I need more accuracy. If you can afford them, the Mitutoyo 0"-1" and 1" to 2" digital micrometers with a fast adjusting thread are an excellent addition to the shop and it is hard to make a measurement mistake.

Thank you for the preferred measurement locations for checking micrometers.

Paul