Bruce - that's true, if the machine is designed that way, in which case the common bore between the bearings would be grease filled, and the whole assembly would work as a single, twin race, grease-filled bearing. As I explained to Tom, this machine was designed with two separate, sealed-on-both side bearings with a significant gap between them. The gap was not grease filled, and was never intended to be, and of the four bearings on the two wheels, 3 were intact, sealed-on-both-side bearings. One was missing it's second seal, and because of the gap between the two, was also dry - the grease having been slung out into the gap over operation of the saw - and consequently seized.

But you're right, dust couldn't get in there, and that part of my initial description was a bit off the mark. The bearing failed from being dry, not because it was full of dust.