Thread: Do urethane bandsaw tyres need to be crowned?

the wheels rims have a crown machined in if it is intended to have a crown, which I believe the carbatec is supposed to have. They will also have a lip machined onto the edge.which is how you tell.

If there is no lip machined onto the rim's edge, it is intended to take a flat tire with the teeth over the edge, which can be replaced with a specially made crowned tire, but that will be a bit thicker, and will move your blade slightly outboard

Originally Posted by T91

the wheels rims have a crown machined in if it is intended to have a crown, which I believe the carbatec is supposed to have. They will also have a lip machined onto the edge.which is how you tell.

Thanks T91, the wheels do indeed have a lip and, if I recall, the wheel where the tyre sits did look slightly crowned as well.

Doesn't matter if the tire is urethane or rubber or whatever but it really does need a crown. Top wheel especially important, bottom wheel less so but if both are crowned nicely then the machine will run sweet.
You can buy urethane stretch on tires that are pre-crowned if they only go on a flat wheel. Sometimes the wheel itself will have a crown machined into the metal rim meaning you buy the tire that is flat and parallel and it forms the crown when it's on the wheel.

Originally Posted by Chris Vesper

Doesn't matter if the tire is urethane or rubber or whatever but it really does need a crown. Top wheel especially important, bottom wheel less so but if both are crowned nicely then the machine will run sweet.
You can buy urethane stretch on tires that are pre-crowned if they only go on a flat wheel. Sometimes the wheel itself will have a crown machined into the metal rim meaning you buy the tire that is flat and parallel and it forms the crown when it's on the wheel.

I can't say for absolute certain, as much of my experience could be down to my upper wheels bearing spacer, but is food for thought for those who may have a similar issue with their machines too, i.e top wheel sloppy in 9 and 3 o'clock axis,
but am under the impression that using substantially differing profiled tires will compress blade set, as I've got a lot of thin gauge blades which are still fairly sharp, but the set is gone on a lot of them,

I guess there's just less mass to have the same resistance to deflect,
which if working reclaimed stuff with putty, one little veer off course and the blade is instantly squished,
so things get from bad to worse in an instant.

What made this less noticeable was using the same width and TPI but a heavier gauge blade with more set, which interestingly required me to have to set the table again (I like my mitre slot parallel)
which I didn't expect.
I'm not sure if I would have noticed the set compressing on these blades, as the machine got noisy shortly enough after that.


Tom

I think you may have other issues here causing set to be taken off teeth. Rubber wheels no matter what the profile won't remove set from a steel blade.
The crown on a rubber tire machine is for tracking purposes, not for preservation of tooth set. That's what the rubber is for, to absorb the tooth set as the blade goes over the wheels. A flat tire no crown will run just fine but the blade won't track nice and wont' sit on the wheels very happily at all. It'll dart forward and back when you look at it wrong or breath on it let alone take a cut in something.
Your thin blades that you say have lost set but are still relatively sharp - If the wheel theory was right then the blades would have only lost set on the side that presses to the wheels and not the other side, inducing some serious blade drift in a cut.
If it's losing set off both sides then it' a few things could be causing that - the material you're cutting, or the guide blocks set too far forward and stripping the set that way, or maybe something to do with material cut and technique in a turning cut that may be giving the set a hard time especially on those really thin hobby blades there isn't much metal in those.