Is the torque release clutch there to make sure it is impossible to strain the mechanism by over tightening or is it to give results that are repeatable if used by different people. ie below the torque release force is the area where grime/gummy lubricant etc would give inconsistent results if measurement was by feel of "first" touch.
Both
The former in the hands of idiots, and the later for all others.
CarlBoyd
Well said. I was taught at school to do three "clicks". When I got to work and watched a machinist, I thought about it. After many years of practice, I now know for sure who was right.
I recently measured a couple of hundred used pins from a large industrial chain. These had some witness marks at the contact sites, but you couldn't reliably estimate the wear from individual measurements across the worn and unworn diameters. However by measuring everything (diameters in two planes and four axial positions) and then doing the stats I was able to show that the worn pins (only pins from some parts of the chain were worn) had on average two tenths of wear on them. The diametral tolerance was about a thou, and some of them had half a thou of taper.
It is never impossible, heck, they can drop it. It is an attempt to mechanically put 'feel' into the mic.
I haven't checked but if the user spins the mic closed on part being measured, I'm sure they can get a different reading regardless of any ratchet or friction system. Inertia you know.
Wes
My set of Starrett 1" to 6" 436 mikes have the ratchet because when I bought them, the ratchetless model was out of stock. I wouldn't buy the friction thimble design because I've seen too many of them with frozen thimbles. I don't use the ratchet, and I wouldn't use the thimble. I trust my feel to .0001" which has been good enough so far.
David
A frozen thimble on a Starrett 436?? Mine will be 40 years old this coming Jan 7. Never had a problem with the thimble.
A couple of the old timers I knew in the business, at Mitutoyo and Starrett, didn't disguise their disdain for relying on ratchet thimbles. The general opinion was that three different inexperienced users, all using the same ratchet mike, would get three different readings off of the same part.
You still need some practice with the things to get consistent results.
-- Ed Huntress
Neither have I, don't use them, as I said. The frozen ones weren't mine.
David
Is there a measuring system where that isn't true? :^)
David
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