Low Speed Grinder Experiment Homemade Machines & Jigs
I can’t recall where I saw it, but this idea is based on a commercially available product that works in the same way. That one looked like it was made from a hard rubber and relied more on centrifugal force as the wheel spun at a higher speed. The lobes or fingers were shaped such that they were more massive at the rim.
My version turns at the lowest speed my lathe will go and uses the fingers as springs to hold the belt on. The wheel is sized slightly over-sized and the kerf cut allow it to collapse enough to get the belt on.
Doing this on the fly using a sanding belt that I bought by mistake (my belt sander takes 24″ belts, this is 21″), the first step was to measure the actual length of the belt on the inside. I did that with a strip of masking tape:
Turned out to be 20-7/8″, which is probably well within tolerance for this type of belt. I used that to calculate the diameter of the wheel I’d need – 6-5/8″.
First only mistake was using particle board core plywood for this. Or at least it turned out that way. Designing this as I went, the base of the fingers need to be fairly thin to allow them to flex to get the belt on, and particle board breaks too easily. When I redo this, I’ll use Baltic birch plywood or some of the plastic I used for the top of my homemade table saw.
The layout looks complex, but two of those circles are for the metal face-plate to mount this on the lathe. The fingers were marked at 10 degrees apart and tangent off the small circle in the middle to get that angle. The fingers need to be angled toward the rotation to keep the belt from slipping (similar to how a feather-board works).
” Not sure if these holes at the base of each finger were needed, I did them more or less for looks…
As shown in the video at the top of this page, I then cut out the wheel and turned it down on the lathe to what I hoped would be the right diameter. This was very much a roll of the dice because after the fingers are cut, it’s a lot more difficult to reduce the diameter.
Not sure if these holes at the base of each finger were needed, I did them more or less for looks. Ever important to keep in mind that the thumbnail image and title gets people to watch the video, and making it look cool or interesting is the way to do that.
The fingers (not mine) were then cut on my homemade band saw:
Mounted and the belt installed, it was a snug fit:
And even better – it still runs true. I was concerned that possibly some of the fingers would close tighter in one area and throw the wheel out of round enough to make it unusable.
I made a tool rest quickly to try out ideas for that. Still needs some fine tuning, but I like how it locks onto the bed of the lathe:
And finally a test grind on a 1/4″ chisel. The belt is 80 grit, so really too coarse for this, but it did a great job of hollow grinding the chisel without getting hot enough to draw the temper from the steel:
Since I don’t use my lathe often, this can stay setup and ready to use. And when I do get around to remaking the wheel from better material, I’ll design a better tool rest and attachment for sharpening knives.