Why does a bandsaw blade not slip off the wheels?
AndrewSmithCanada
| Posted in Power Tools and Machinery on
Hello
I’ve reently set up and adjusted my new used bansaw and it works pretty well.
There’s still on thing I don’t understand though.
On every other wheel-and-belt system if the wheel doesn’t have ridges (or at least is convex) – the belt will ride off the wheel either on its own or with just a little pressure.
On a bandsaw where the band is quite thin and the wheels are narrow and concave – I would expect the blade would slide right off the wheels as soon as you started pushing material into it.
But it doesn’t. In fact even though my rear bearing guide is very close to the blade – I never even had the blade touch the guide.
Does anyone here understand the mechanics that keep that blade centered?
Thanks in advance.
Replies
I can't go through the actual physics behind it but, I'll tell you what I know. Making the blade stay on depends on at least 3 factors: wheel alignment, tire crown, and the bearing behind the blade. First, the wheels must be co-planer. This means that the vertical center lines of the two wheels must align with one another. Second, the crown on the tires is there to keep the blade running true. Because of the crown, if the blade wanders off track slightly, the pressure on it changes and causes it to go back to center. It is rather like the caster setting on car front wheels or a bicycle front wheel. This is why, when riding a bicycle, you can remove your hands from the handle bars and steer it by leaning one way or the other (within reason). Third, if you put enough pressure on the blade with the rear bearing loose or missing, you probably could push it off. So keep it adjusted according to specs.
The blade may not touch the bearing you can see -- the top bearing. But it's almost certainly contacting the bottom bearing.
It’s the same principle that keeps flat belts tracking, it’s called crowned pulleys and explained here : https://woodgears.ca/bandsaw/crowned_pulleys.html
Thanks Gulfstar, I would have never figured that out by myself!
This forum post is now archived. Commenting has been disabled