Help centering something on rotor shaft

[sushi]

Hello guys, I don't even know the terminology for this, but I have a flexible shaft tool that has a cable which attaches directly to a motor shaft. The cable has a little cup that slides over the rotor shaft with a set screw, but the cup is a little bigger than the rotor shaft so it is off-center and vibrates when it rotates.

Is there some way to center this? Like some kind of collet or something I can put on to make it perfectly centered or build up the motor shaft so it is a little bigger?

(these are example pictures from the internet but they are the same as mine)

Here is a picture of the cable, the brass cup goes over the rotor shaft:



And here it is attached to the rotor shaft:

[cshplumber]

Have you tried some tape around rotor shaft? Duct, electrical, 10mil.... How big is the gap?

[sushi]

I have not, I did stick a little piece of newspaper in there folded in half so it took up like 1/2 of the diameter in there and it helped but it is not perfect. The gap is pretty small, too small for one layer of electrical tape, but I think teflon tape might work!

I was wondering if there was a more precise solution since this spins at 18,000 rpm, even a little off center it causes problems. If it is perfectly centered it will be perfectly smooth, but I bet I can get it pretty close with teflon tape.

[crabbysd]

You may be able to use a cheap feeler gauge set and cut one of them. Ive used them to shim camera lens mounts
https://www.google.com/search?q=feel...gauge&tbm=shop

[sushi]

Oh man, that is a super good idea. Thanks crabby, that's perfect! I can get it exactly right and it'll never give.