a very good point was brought up. owning your own tools is a good start, but learning how to use them is even more important. I've tried to teach people correct methods for consistent readings but it takes a long time to truely master. take your time and practice. you'd be surprised at how many people don't know how to read a mic, let alone use it properly. it's not rocket science but it is a learned trade like many other things. try to find someone to show you the basics that is knowledgeable and try to see if your readings are consistent with his/hers. practice until the tool becomes an extension of yourself.
i know of many people that have called their machinist to tell them they're measurements are off, only to be embarrassed. that's the best advice i can give anyone that has no experience with such tools. best of luck to you, we all had to learn the hard way at some point or another.