While discussing the subject with and old timer many years ago, he told me he could set an OLD style set of callipers (the ones that look like a set of dividers) to exactly 1", using only the callipers and a steel rule.
After poking around in a mountain of interesting things piled on his bench, he pulled out a rule and promtly set the callipers to 1". He then handed them to me with a 1" gauge to check. Sure enough they were bang on, I couldn't have done better with a micrometer.
Of course I had to ask him how he had managed it. He told me that on a quaility rule the division lines should be .003" thick. All he had to do was get the calliper legs in the middle of the .003" wide lines.
OK, how he did it I can understand. But how he managed to do it in his dark cave of a shed with the only light coming from a dirty, tiny window on the other side of the room I'll never know. I could barely see where I was putting my feet in amongst all his jumble of half finished projects, tools and curiosities.
It's amazing what experience can teach. A true engineer that one.
After poking around in a mountain of interesting things piled on his bench, he pulled out a rule and promtly set the callipers to 1". He then handed them to me with a 1" gauge to check. Sure enough they were bang on, I couldn't have done better with a micrometer.
Of course I had to ask him how he had managed it. He told me that on a quaility rule the division lines should be .003" thick. All he had to do was get the calliper legs in the middle of the .003" wide lines.
OK, how he did it I can understand. But how he managed to do it in his dark cave of a shed with the only light coming from a dirty, tiny window on the other side of the room I'll never know. I could barely see where I was putting my feet in amongst all his jumble of half finished projects, tools and curiosities.
It's amazing what experience can teach. A true engineer that one.