A slight diversion from the usual topic of mine, but i hope youll forgive me. A friend of mine is looking for a flywheel/fan for a Stuart air compressor. He's had no luck finding one to press..... I believe a copy or something similar could be made from an Ali casting. So I'm looking for info on making a pattern. The picture posted below I've done some scaling on, dimensions i have are as follows. OD=5" Width of tread=0.774" depth of tread= 0.221" Hub OD=1.144" Width of hub=0.774" Width of blade=0.717" Thickness of blade=0.100" Can anyone confirm or correct these sizes please? I assume that the castings would have been made to imperial sizes originally, so for example the hub OD, of 1.144", it would have been 1.9/64" which is 1.1406", or 1.5/32" which is 1.563". The width of tread, 0.774" would be 25/32" which is 0.781" Just looked up shrinkage for Ali, and it's 6%, (5% for brass if anyone's interested) so the overall dimensions of the pattern would have to be 6% bigger, and then the machined faces (outside OD, and tread width depth, hub width) another 1% minimum ontop to give enough material to machine away to finished size. (Ps gosh my heads getting a workout tonight, it needed it, blow away the cobwebs�� I was planning on making a pattern from plasticard, one because that's the material im used to working in, it can be laminated to any thickness and turned easily on a lathe at reasonable slow speed. It can also be sanded to final finish and extra material added to the pattern if one is a little heavy handed with the sandpaper. Can anyone confirm the sizes posted above, provide an original machined casting to measure, or let me know if plastic patterns can work, I've seen 3D printed patterns work well??????