Also have a look at Etalon micrometers. Imperial versions pretty cheap secondhand, but make sure they are still in excellent condition. Go for the ones with vernier scale for resolution of 1/10th of a thou. If you want to achieve repeatable limits and fits this is genuinely useful. However, you will also need the mics calibrating - or get a slip gauge set and do this yourself. Without knowing your measuring tools are fully in spec, you will struggle to achieve tolerances under a thou.
I use a metric slip set for calibrating imperial mics. (I had a spell working in an aerospace standards room ). With care, measurements can be accurate to a couple of 10ths of a thou but cannot be taken for granted. Lots of care and checking needed. Use of a very sensitive dti and comparator stand also helps to keep things correct.
Realistically I can measure and turn to within a thou and grind to 1/10 of a thou (making engine components). Honing machine also good for 1/10 of a thou. Measuring to that 1/10 of a thou in a home workshop though is always pretty challenging. Remember that you will also need excellent bore micrometers - these tend to be very expensive. If you just need to make one offs and do not need interchangability, using comparators saves a lot of expense.
Absolute favourite micrometer is the Etalon Microrapid. Very, very accurate and super to use. Very tricky to rebuild so be careful if buying second hand.
Never have liked digital mics. These can tend to “deceive” with a high resolution displayed on the readout but not actually bearing true with proper inspection!
