6x48 Belt Sander with both drums crowned....
Posted: Sun Nov 17, 2019 9:35 am
My 1987 issue 6x48 belt sander came from the factory with both drums crowned. I understand this was a mistake that lasted for some time. The effect is that the sanding belt tracks poorly. In order to keep the belt between limits it requires constant fiddling with the tracking wheel at the nose of the sander. I never owned or used a 6x48 belt sander before so I didn't know any better.
Once I learned about the error (last year!) I considered purchasing a replacement drive drum without crown or having it machined. Without anything to lose I ran it without a belt and used my disc sander disc to machine/sand the rubber tyre flat. (I held the disc against the uncovered drive drum as it spun driven by the headstock.) I wasn't patient enough to go all the way, I did create a flat section in the middle of the drum about 4 inches wide. When I tried using my belt sander with the mostly un-crowned drive drum I found it now tracked perfectly. No fiddling as I sand these days!
I also replaced the clapped-out shielded bearings with new sealed ones. Lubed the front drum too. All set for another 40 years and no bearing whine either!
Once I learned about the error (last year!) I considered purchasing a replacement drive drum without crown or having it machined. Without anything to lose I ran it without a belt and used my disc sander disc to machine/sand the rubber tyre flat. (I held the disc against the uncovered drive drum as it spun driven by the headstock.) I wasn't patient enough to go all the way, I did create a flat section in the middle of the drum about 4 inches wide. When I tried using my belt sander with the mostly un-crowned drive drum I found it now tracked perfectly. No fiddling as I sand these days!
I also replaced the clapped-out shielded bearings with new sealed ones. Lubed the front drum too. All set for another 40 years and no bearing whine either!