A good set of calipers can and are very accurate when still working used them often to measure + - .001. Now i did say a good set i always preferred browne and sharpe but starret and mityo are good to. I have to say if you are flexing a pair of calipers you are pushing to hard. I used the same brown and sharpe calipers for over 40 years. Calipers have adjustment screws on them to keep them zeroed as they wear. Just like a micrometer you have to have a feel for a caliper. Pretty much anyone can do it just takes practice. When ever we had new people starting out set them down with a set of joe blocks and a caliper and mic so they could kinda get a feel on how to measure .