Making an EV Motor Template vs buying a trasn adapter
 

Is making your own electric motor adapter a bad idea due to lack of precision and the problem it could create, or do you just put the hub on, make a template and the tolerances are close enough?

Thanks!

Nope, I have made my own bracket and flange adapters for years. You just need to have the right tools, materials and be close enough.
If all you need is a flat plate that is 1/4, 3/8 or 1/2 inch thick than you can DIY.
If you need different spacing, then it gets interesting, but not impossible.

Here is my latest adaptor plate. Used my plasma cutter, drill and intake porting tools.
It addapts a more fuel efficient non-turbo duel plain intake manifolt to a very efficient upper plenum used on a turbo manifold.

F-code/J-code adaptor - Diesel Place : Chevrolet and GMC Diesel Truck Forums

Even how the factory gas engine mates up to the transmission is not perfect, they are two different parts often made in factories many miles apart, so when you make your electric motor adapter you have the potential to make it match better then the gas engine did, you also have the advantage of being able to bolt the motor up to the transmission and with the bolts loose a turn or two run the motor at low speed (12v battery) while shifting the plate around slightly until it feels and sounds like it's running smoothly without any bearings binding, you can't do that with a gasoline engine even tho there is the same slop.