bandsaw thrust bearing

[jonboy]

I'm new to this, but acquired an 80" blade bandsaw missing the top guide post set-up.
good time to upgrade by fitting the roller bearing after-market kit, of upper and lower guides and bearings... Question The thrust bearing on both assemblies ( the single bearing running at the back of the blade)... is 'side-on' why not have it running like a wheel against the back of the blade, and I see some saws do that.
Engineering principle suggest sealed roller and ball bearing races are not meant to have lateral in-line-with-the-axle force, though thrust bearings are of course, but these seem like ordinary little jobs the same as the side guide bearings....
thoughts anyone?

[Ron Williamson]

I've wondered, too.
We have two set up that way and one set up the other way
My conclusion has been that it's because the 'side on' plane is flat, the load gets spread to more bearing surface,and the bearing surface is closer to the work.It also is easier to adjust and simpler to build, than one that's setup the other way
One of ours has bushing/cap pressed onto the guide bearing for much better protection and longer life.
R

[jonboy]

the cap sounds a good idea, but with the 'side on' it seems there has to be some skidding of the back of the blade over the side face of the bearing....however minimal, but avoided by the other set up...

[Ron Williamson]

The cover has a step in it,so it's higher in the middle with 45degree transition between the two.The blade rides close to the transition.
The side bearings are set up the same way,ie.opposite to the way that they 'should be',but with no cover.
The side bearings are also a bit lower and keep things aligned sideways.
Check this,though
http://www.youtube.com/watch?v=w_tv7cm0-VU
R

[Mrleft8]

The bearing shouldn't spin at all with the blade under no load. But should spin the instant you feed a piece of wood into the blade. A sharp blade will not require enough pressure to ever harm the thrust bearing. I have both side, and in-line thrust bearings, and if anything, I'd say the side mounted bearing offers a little more control....

[Torna]

I can think of two reasons that (at least traditionally) the thrust bearing was "side-on"
1) it's very simple to implement accurate fore&aft adjustment by threading the the bearing's axle. Using a "wheel" thrust bearing will require some slide mechanism with a locking arrangement (thumbscrew) and precision becomes important - see #2.
2) if thrust bearing is arranged as a wheel, over time the back of the blade would wear a groove in the wheel. This will cause steering problems every time the lateral guides are adjusted and, if there's lateral slop, every time the fore&aft position is adjusted. The "side-on" bearing's face should wear evenly so even though it doesn't appear to be mechanically optimal, it'll never create a steering problem.

Early bandsaws were also made very crudely: big castings & crude machining capabilities put an emphasis on simplicity and lack of required precision. Modern manufacturing techniques are much better; the amount of precision designed in a modern set of guides was inconceivable 100 years ago. Also the hard alloys available to make thrust bearings, and low replacement cost of them, is very different than it was back then. So modern machines may well make use of wheel-style thust bearings. If/when a groove develops in the wheel it's $5 and 5 mins to replace it - very different.

Them is my 2c
-leif

[Mrleft8]

The Carter guides thrust bearings come pre-grooved. If you're putting enough pressure on your thrust bearing to wear a groove in it you need to have replaced your blade 3 years ago ;)