The steel platen behind the belt has been a bit problematic since the start. As you can see in older pictures, it was a piece of angle iron that was on the left side attached to the belt-grinder arm with two screws. The problem was that when I exerted pressure on the right side, it bent ever so slightly and the belt started to wander off and the whole thing behaved a bit unpredictably. I learned to work around the problem, but it was a problem and it needed solving. So this week I finally solved it.
I bought two hinges and screwed them on a piece of 3×40 mm mild steel at a distance slightly bigger than the thickness of the belt grinder arm. Then I drilled two holes through the arm and put in them two carriage bolts with winged nuts. Then I cut slots into the hinges that I could slide under the screw heads and the nuts. Because the hinges are slightly more apart than the thickness of the arm, when I tighten the screws they work as flat springs with a slight bend and it all holds together very nicely.
To serve as the platen I have screwed a piece of 10×50 mm mild steel on. It works perfectly. It is stable regardless of which edge of the platen I work on and I can exert as much pressure as I want, although admittedly, I have only ground bone on it and not steel. I might either harden the platen by carbonitriding it or I can weld a hardened steel plate on the face, but mild steel works just fine too and with my rate of making blades it will hold for a long time as it is.
There is one last problem that I need to solve, and unfortunately, I do not know how. It is also difficult to describe, doubly so in a foreign language, so if you do not understand what I say, the problem is probably not at your end.
I need a reliable and stable way to adjust the belt’s traction. The spanning arm was a bit wibbly-wobbly, and when I fixed that, I got new problems. When I optimized it for a forward-running belt and tried to run it in reverse, it wandered off to the right and fell off. And when I optimized it for a reverse-running belt, it wandered to the left and bit into the arm. After a lot of faffing around I managed to get the belt stable in both directions – but then it was off-center and the sideways position of the spanning wheel had no influence on it whatsoever. The spanning wheel is crowned and that should make the belt tend towards its apex and thus I should be able to move the belt sideways, but it did not have any influence – the same thing happened whether it was near the arm or as far from it as it could go. Only the tilt of the wheel had an influence, but when I fixed the wobbliness, I lost the ability to tilt it.
I have managed to get the thing running by bending the screw on which the spanning wheel is fixed. When I turn the screw now, the wheel tilts, and I can adjust the belt. The problem is that it is too responsive and not very stable, just like it was before. I am wracking my brain for solutions, but so far I have not come up with any that are doable with my equipment.