Shop calculators and references

Working on a project that has me wondering what are the most useful calculators and references when you are working in the shop?

I have a Machinery Handbook, but it is not a shop reference. Too hard to find what I want and usually way more details than I need in the shop.

The most useful things to me are:
Drill chart listing number, letter, fractional, metric with their decimal equivalent.
Tap chart with drill sizes for both cut and roll taps.
Drill point calculator for various common point angles.
Trig calculator that solves right triangles.

One thing I also use but less frequently is a calculator that figures the dimension over or between pins to measure dovetails.

So what other references or calculators do you find yourself using on a regular basis in your shop?

Tim Goldstein
A2Z Corp
3955 S Mariposa St
Englewood CO 80110
P 720 833-9300

www.a2zcorp.us/store