Thread: big dremel mandrels?

Dremel does make screw mandrels--one end is just a open screw that you screw into the wheel. They're mainly for felt wheels, I think.

But as mentioned, just putting a screw through it should work. I've done that when I tried to make some dremel wheels.

Would I need a regular thread or a reverse thread? I suppose that I would also need a screw that wasn't threaded all the way to the bottom. It would require a smooth surface to fit the mandrel.

Can you not just get a longer machine screw and washer and put it in place of the original dremel mandrel screw? I've done that for similar bits with no issues. Any hardware store should have long machine screws in that diameter.