I recently purchased a brand new O.S. Max .37 heli engine. I think that
it came with a bad prop nut. When I look at the threads on the
crankshaft they look perfectly fine and the cooling fan screws on
easily. But when I tried to screw on the prop nut it was very hard to
screw it on. I only tried to screw it on with my hand because I did not
want to cross thread the crankshaft. I'm not sure what the propblem is.
Do I have a bad prop nut?

You most likely hve the wrong prop nut, it's neither bad nor good. Take your engine to a hardwre store with a good selection of US and metric fasteners, you will find one that scfrews on well.

I suspect you are trying to put an 8mm nut on a 1/4-28 thread.

Bill.

8 mm nuts are usually confused with the 5/16 - 24 threads.

This was probably a 6 or 7 mm nut if it screwed on the shaft at all?

You best do like Bill says.

Enjoy,

Jim

Jim:

You're right. I should have said 7mm.

Bill.

ok, thanks guys. I wonder why OS sent the wrong prop nut with this engine.

Stuff happens?

Pick up from here and go to the bolt and nut store. It'll be cheaper than getting into a witch hunt with the OS network.

Enjoy,

Jim

D:

As much as they hate to admit it, Japs are human too, and make human mistakes.

Bill.