There's one called Math for Pipefitters that has a lot of good math and layout formulas in it. I think the author is John Hamilton but I'm not positive. I don't know if my book is in storage or not. I'll check and write in the author if it's not. Also there are some cards called Chico's Pipefitting Cards with a lot of the more common formulas and stuff you will use every day. If you can learn how to do all of the offsets on those correctly you'll be ahead of most of the so called "fitters" I see today. It used to be you had to know more than how to put pipe in from point A to point B but there is such a labor shortage nowadays that most companies are pretty happy if a guy shows up most of the time it seems like!!!! As an inspector I would dearly love to work for a company that would let me test fitters. It sure would save them a lot of headaches in the long run. I used to ask my "fitters" what half of 5/16ths was and you'd be suprised how many of them started to get out a pad and pencil or their calculator!!! I would just go tell my foreman I needed another one. . .. .