One thing that model engineers enjoy is a bargain, and you can’t get a better bargain than free, I refer to the MODEL ENGINEERS COMPANION, a free software program distributed by the Gravesend Model Marine and Engineering Society. http://www.gmmes.co.uk
I have this program on my computer desktop and find it very handy when planning projects, for quick reference to imperial / metric conversions, thread, drill, sheet/wire and nuts and bolts.
Please download it and give it a try and if you don’t like it you can always delete it.
Bert Ashton