While making my Drive Gear, I needed to true the disks, that is, to make all of the disks the same size and perfectly circular.

I started out by inserting a length of dowel into the center hole and, using the hubs that I had made, securing the disks to the dowel.

The dowel was then inserted into the chuck of the drill-press and the drill was powered up.

This made the disks spin at a fairly high speed so that I could run a rasp over the ganged disk edges evenly to reduce the diameter evenly.

The problem with this approach is that the dowel breaks and the whole gang of disks then flies off at high speed ... dangerous!

My solution was to make a spindle shaft out of some threaded rod and fix a nut at the bottom of the shaft against which I could secure the disks. This is a pretty short instructable, and one that I hope is easy for you all to use and enjoy.

Materials:

5/16" threaded rod
2 x 5/16" nuts
1 x M4 x 12mm bolt
2 x 5/16" washers

Tools

M4 tap
5/16" tap
tap spanner
drill

Step 1: Drill and Tap

I first flattened the bottom 5mm of the threaded rod and drilled a hole for the M4 bolt, then I drilled a hole in one of the faces of the 5/16" nut and threaded it for the M4.

To remove the burr from the inside of the 5/16" nut, I ran a 5/16" tap through the nut.

The reason that I'm using an M4 bolt through the 5/16" nut is that when the drill spins, it will spin the nut from the bolt. The M4 is there to hold the 5/16" nut in place.

There is no need to drill the nut at the top of the threaded rod as the drill motion will tend to drive the nut down toward the bottom, so it will tighten it.

As far as the tool goes, that's it ... there is your spindle right there.

The threaded rod was made long enough to fit the disks plus the 2 washers and 2 nuts and leaving enough length left over to fit into the chuck of the drill (I left 5cm).