Re: What is this tool?
One of the many uses of a "dial indicator" is to measure runout -- the difference between the high and low spots on a part. For example, you may want to know how round a part is. Place the dial indicator in contact with the part, zero it out, and then spin the part. The movement of the needle will show you the variation.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.