- Joined
- Apr 14, 2014
- Messages
- 3,189
I go back to the last 2 sentences in my previous post. "In this incident the OP is "assuming" the micrometer is properly calibrated and the gauge block is in error. It could very well be just the opposite." Without a controlled atmosphere how can the OP be certain which component is causing the difference from the measurement stated on the block. Simply handling the block long enough to raise the temperature a few degrees can cause the dimensions to change. Given a micron is .000039" and tool steel expands at a rate of 12.8 microns per degree, it would take less than a 5* change (from the standard of 68*) in temperature for a block to expand .0001". Any lint or even a finger print on either on the micrometer or the gauge block could account for the difference in measurement.
I agree with John York's assessment of the use of gauge blocks in a hobby shop. Mine were originally purchased to setup a sine bar. I must admit however I have been known to use them to check the accuracy of a micrometer. I have a number of micrometers in the shop. The newest were purchased in the 1980's. The oldest date back to WWII. Even the oldest ones are good to within a tenth. That's close enough for anything I do.
I agree with John York's assessment of the use of gauge blocks in a hobby shop. Mine were originally purchased to setup a sine bar. I must admit however I have been known to use them to check the accuracy of a micrometer. I have a number of micrometers in the shop. The newest were purchased in the 1980's. The oldest date back to WWII. Even the oldest ones are good to within a tenth. That's close enough for anything I do.