Easy ball bearing centering

I was very interested by this thing : https://www.thingiverse.com/thing:2165694

Thanks to [bxd2000](https://www.thingiverse.com/bxd2000/about) for sharing.

When I placed (or pressed) the first ball bearing into the "laufrad_0.2_tol.stl" part, I realize that the ball bearing was not well centered as the thickness of the two parts are not the same.

That's why I designed this part (printed twice) to guide the ball bearing into the weel and center it.

That's it. This part is only usefull if you want to print your own spool holder having the ball beraing centered. Enjoy!