Three weeks ago one of the idler wheels on my belt grinder gave up the ghost with a screech and a puff of smoke. I was wondering why everything was overheating lately – the belts, the platens, the hweels, teh hwole heveryting. As it turns out, one of the ball bearings on one of the idler wheels was probably a bit off and when a ball bearing starts to go bad, it gets only worse from there. I have impromptu repaired the wheel but I have decided to take this opportunity to rebuild and improve my belt grinder.
The first step on that path was buying a bunch of precision-cut aluminum tubing.
The only downside was that the ball bearings fit too well into these tubes, they could be inserted without any effort whatsoever. And I do not have a lathe to cut grooves for internal snap rings. So I have used stainless steel foil strips as shims for one ball bearing to press it firmly into the tubing with the other ball bearing only inserted and held in place with the nut in the assembly.
Here you see one of the new wheels before it was assembled on the belt grinder. Aluminum tube with one firmly pressed in ball bearing, steel spacer with a piece of cork to hold it somewhat centered (I have drilled the center of the cork a lot more later on so that the spacer is really loose. The cork is there only so the spacer does not wander too far off center when assembling/disassembling), and the second ball bearing.
I have made three such wheels, and over one I have pressed another aluminum tube to increase its diameter. That one I later fixed in my drill and with the help of my impromptu repaired belt grinder I gave that wheel a barrel-like profile. Because my old tracking wheel was too getting worn and I decided to completely rebuild the spanning arm.
Here you can see the right side of the spanning arm with the new spaning wheel. I won’t go into technimicical details. Here you have a second picture of the left side, it should be worth a thowsand words.
This is in part made from new materials. The downside of this assembly is that I had to weld a 30 mm M10 nut onto the arm. Which was not easy. To say that I suck at welding would be to grossly and immodestly overstate my abilities. When I die, the average welding ability of humanity will probably go ever so slightly up. But after a few botched attempts, I have managed to make welds that at least hold in place, even when they look completely craparooni.
The tracking wheel is on an M10 thread rod and thus can be moved left-right with the help of the upper handle. That is necessary to at least somewhat center the belt on the tracking wheel to avoid asymmetric wear of its surface, My previous assembly did not allow for this and as a result, the wheel got really worn on the left side only.
The second screw under that allows for slightly tilting the spanning arm left-right. That moves the belt slightly from left to right, allowing it to center on the platen. This was starting to be difficult with my previous arm, in part because the assembly was a bit too sensitive (short pivot point) and in part due to the asymmetrical wear on the tracking wheel.
I have used the improved belt grinder for a few hours and it seems to work well. When the current batch of knives is in the tumbler, I will coat the wheels with PVC plastic and perhaps start making some other attachments for the belt grinder.