just curious here but micrometers create do there thing via a gear train, right? It would seem that accuracy would not be an issue with no-name and cheep tools, you ether have the right tooth count or you don't. So I am asking ( and speculating) that the difference in cheep vs high quality is not in accuracy but rather is things like how smooth the action, is it repairable (parts available etc), will the anvils last, and all of the usability things. I guess there could be some backlash in the gear train of lower quality mics but I would think that would be in the tenths range for even a low quality tool.
I'm not trying to stir the pot here, just curious if I am mis-understanding how mics work and where higher quality design and manufacturing of a mic will show up in practical use.
At the bottom line, a "micrometer" is
properly known as a micrometer caliper. As a step up from a vernier caliper, it is essentially the same as a dial caliper. Most times, I can interpolate half a thou on a dial caliper. A micrometer consists of a 40 pitch mandrel with the plunger running thereon. One rotation of
any 40 pitch screw moves the tip of the screw 0.025 inch. On a "mike"(properly mic), the tip of the screw and the anvil it presses against are carefully shaped square to the moving ram and hardened (& possibly lapped) so that the same measure is acheived regardless of position. With a strongback to hold the parts under pressure. The "C" shaped bow. . .
From my distant past, I have several (1/8, 1/4, 3/8, 1/2, etc) 40 TPI taps. They were for fitting adjustment (or calibration) screws on archaic measurement instruments. What and how they were actually used is outside the frame of this discussion. What is relevant is that they worked the same way as a mike, one rotation of the screw moved the tip 0.025 inch. From a theoretical perspective, I could build a special mike on a shaft of the same diameter as one of these taps.. The threads could be single pointed on the lathe. The follower could be tapped the same pitch, the hole left intact or shaved by a half to make a lifting mechanism. Essentially the same way half nuts fit the lead screw to make threads on a lathe.
The "complexity"of a mike is really non-existant. The precision and repeatibility are what matters. The only "complex" part is that it is done so small as to be a one handed shop tool. The many manufacturers realize "quality" as much or mostly through the smoothness where parts fit together, smoothness of finish, and the square grinding where the tips meet. In most any other perspective, once they are trued, calibrated to zero, there is little difference between Mitutoyo and Harbor Freight.
A metric micrometer works the same way, just with a metric thread on the screw. I have a couple but have not dismantled one or analyzed the dial. I don't use one very often, doing many of the conversions in my head as I work. Probably a 0.5mm pitch, but I'm not sure. . . Looking at how far the tip travels in one revolution defines the pitch.
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