Wheel Mandrel

Sometimes, wheels get damaged or worn. Sometime you want to reduce the size and weight of a wheel. Sometimes wheels are not very concentric. If i ever get around to making my own wheels, the last step in the molding process should be cleaning up the rolling surfaces.
Those are the times you want a wheel turning mandrel.

The tool is pretty simple. It imitates a bearing on the driven side, with a movable shaft collar to increase the radius of friction for better drive. There is another half of the tool in the tailstock, which has a real bearing on a dowel pin, all pressfit into a little holder.
The wheel is inserted onto the driven (left in images) side and the tailstock is then extended to clamp the wheel between the collar and the bearing, with the alignment assured by referencing the central pin and the bearing bores in the wheel.
You can then resurface the wheel, changing corner radii, creating large-scale texture/grooves, or just reducing the OD or width.
The tool was designed to be very quick to change wheels, so you can process a whole set of wheels very quickly.

One interesting trick during fabrication was reaming the hole for the pin in the driven side. I needed a clearance fit, but didn’t have a correctly sized ream. I’d heard of a trick to slightly oversize a reamed hole:

  1. Ream hole as usual.

  2. Wrap a paper towel with cutting oil on it around the reamer.

  3. Ream again. The paper towel will rip/cut on one side, but not the other. This means the reamer is being slightly offset by the thickness of the paper towel on one side.

This trick worked great, creating a very nicely oversized hole that clear the dowel pin, but still creates a nice airtight fit. With a little oil, this dowel pin will act a little like a plain bearing.

Todo

To process inline wheels, i really need a radius cutting tool. This would allow me to apply very small cutting forces but create very large radius cuts a little at a time. When using a traditional form tool with this type of (frictional) work-holding, there is a significant risk of the wheel spinning in the bearing seats. Perhaps if the shaft collar had some little pointed setscrews in it, or skateboard griptape, there might be some more mechanical connection between the side of the wheel and the driven side, allowing higher force cutting tools to be used.