How to fix a flat spot submitted by Eric Irwin
This weekend I figured out a way to "fix" a flat spotted wheel. I have only done this once, so I don't know how it will work on all wheels or all flat spots.
It requires the use of a belt sander, which I am aware that everyone will not have, but if you look around, you probably know someone that does. I used an 80 grit belt this time, but want to try a 120 grit the next time.
Start by clamping the board down (wheels up) to a solid piece of something, I used my workbench. Turn on the belt sander and run it across the wheel at about a 70 degree angle to the plane of rotation. You want to ensure that you are not sanding the wheel into a cone, so you've got to keep it flat to the wheel surface. The rough dirty surface of the wheel is a good indication of how level you are sanding. The wheel will spin pretty fast, but not fast enough to damage bearings or anything. As you pull the sander off the wheel, you can touch the wheel and and feel if you have removed the flat spot. Just keep repeating this until the wheel is round again.
You are putting a pretty severe side load into the sander. Be prepared for this and have a good hold on the tool. Also, this side load will tend to push the belt off center, so you may have to pull the sander away and let the belt re-center itself and then start again.
I ended up removing about 1/2 mm from the diameter of my wheel. I can still slightly feel the flat spot, but it is about 95% gone. I did put a little bit of a cone in my wheel, but that's what happens when you are experimenting. It is good enough that I don't feel the need to replace the wheels anymore.
