You are clearly useing a different set mic's and calibers then I do. Mine have to be checked every day to make sure their accurate and ASTM comes in once a month to check them as well.We also use the check blocks as well up to 1 inch for mic's and for our DIAL calibers you just have to unlock and turn the face to zero and relock. our mic's donot have number readouts like most, those are a pain. What I use you just loosen the nut on the end of the handle, close the jaws and turn the handle to zero and tighten the allen nut on the end of the handle, no case to split, no gears to move. I work with .001 tolerances all the time,no more, have been for 30 years and thats all the tolerance you really need for reloading. The number readout mic's can't take very much abuse, drop one and your done half the time and yes you do need a spanner wrench and allen wrench with that type.I have used jaw type dial calibers and yes you split the case and reset gears, but if you let the jaws slam together on closing they will jump zero. They were junk and we quite useing them after a few weeks and they were starretts. A good quality 6" dial calibers that can be reset to zero by moving the face ring ( 2 sec's)and a non number readout mic is the simplist to use and maintain and should last a life time and cover most reloaders needs and tolerances. A target shooter may what tolerances in the .0001 are better range but basic reloaders, the .001 range works just fine.