My tracking wheels made from alu-tubing had a diameter just 30 mm, so the ball bearings were running really rough when at full speed. and they chattered and were generally noisy too. I have been thinking for a long time about how to make bigger and better wheels. I tried to glue soft PVC on the surface. That stopped the chattering and added ca. 1 cm in diameter, but when it ran at full speed, the PVC was ripped off. I tried to glue on leather, and the same happened. And now I hope I have finally found a solution – to make them from micarta.
I have used a technique that I learned from my older brother as a child when making paper car models. To get nice and sturdy wheels for those models I wound a glue-covered strip of paper around a wooden skewer until I reached the desired diameter. One could get nice, sturdy, and round-ish wheels that way. Later in university, I used the same technique to build a complete chess set (I still have it). So for the wheels for my belt grinder, I soaked strips of cloth in epoxy resin and wound them around the (scoffed and thoroughly de-greased) alu-tube that is the core of the wheel until the diameter was approximately doubled (that should halve the rotational speed of the ball bearings and thus reduce noise and prolong their life).
After that, I put the whole thing in a plastic bag and I sucked out as much air as possible with my vacuum pump. I could not do a very good job of it and I also could not seal the bags very well, but I think it was good enough.
After the epoxy was thoroughly hardened, I cut the excess on the sides and pressed the ball bearings in the tubes. I did not cut the sides very well on one wheel, but that should not be a problem. The wheels also were not exactly round at this stage. This was the snag that stopped me from doing this a long time ago. I knew they wouldn’t be very precise and I do not have a lathe that would allow me to make them really round. But last week I finally got an idea of how to make them round with my belt grinder.
First I have made a fixture for the wheels from 5 mm mild steel and a piece of board. I could span the wheel on it and push it against the platen of the belt grinder, fix it with a clamp, and then with a slowly running 40 grit belt (and very carefully) I could grind it to a roughly circular shape concentric with its rotational axis. The result was a rough and round-ish wheel and I managed to not hurt myself too badly, only one fingernail is now thinner than it should be. I did not take pictures of that, because I forgot.
To get a smoother surface I ran the wheel against a slow 100-grit belt a bit and then I changed the direction of the belt and used wood turning chisels and fine abrasive cloth to further improve the surface.
And it worked reasonably well. The wheels are not perfect, but they chatter less than the previous ones and I expect that with wear the surface will get smoother. If not, I will try to coat them with epoxy mixed with a fine sawdust and polish them again. The advantage of micarta is that It glues well so I can re-surface the wheels at any time. It is also tension-strong so there is no risk of the wheels exploding or cracking mid-work.
Now I will make a new, thicker spanning wheel this way too. And I will add a few mm micarta on the motor wheel as well because it too is not exactly concentric and that too introduces vibrations and noise. This opens a lot of opportunities to make better concentric wheels of different diameters – I still need 3 and 4-cm wheels for grinding fullers and finger grooves and I might need other diameters in the future too.
It unfortunately also means I have to make a new platen. I have jerry-rigged the old one so I can do some light work on the grinder as it is now, but It is not as stable as it used to be because it was built with smaller wheels in mind. But I am working on that problem already and I do have ideas that I think will work. I am also planning on making a new jig for grinding fullers.