So you get out there. You check guide alignment, adjust the tension, and sharpen the blade. You make clean cut and feel good about yourself.
That’s when you hear it. You hear that unmistakable thwack of your bandsaw blade jumping off the wheels, wrapping around the tire, and ruining your afternoon. It doesn’t matter if you’re an expert or novice, you’ve just been band sawed.
And that is very annoying. But then again, this isn’t a “bad-luck” kind of problem. Typicaly it’s a sign of something mechanically out of whack.
A bandsaw is well-adjusted machine; the tension need to be right and everything must be aligned properly. One variable off, and the entire system goes haywire. Once you know how the blade came off the wheel, it will come back on and stay there forever.
Common Causes For Bandsaw Blades Falling Off
Instead of merely rethreading and praying. Bad blade tension is the biggest problem. Woodworkers tend to underestimate blade tension.
Bad Blade Tension
When you change direction or cut denser material, a loose blade twist against the wheel rim. It jumps out of the groove and wraps itself around the tire. This is not good.
It is simple solution but takes some practice. Learn what the right tension feel like. Or use a tension indicator and pluck your blade.
It should sound snappy with a higher pitch then a loose blade (too loose). That said, don’t overtighten because that can damages the wheel bearings and warp the blade. Misaligned wheels is another common cause.
Misaligned Wheels
Both bandsaw wheels should be exactly parallel to one another. When one leans in or out even slightly, it causes the blade to veer away from center. Continued use result in the blade being knocked sideways out of its groove in the wheels.
This is easily tested with a straight edge across the wheel rims. A gap indicates that the wheel trunnions need adjustment. Fortunatly, most older bandsaws (such as Rikon and Delta) feature adjustable trunnions.
Newer ones, such as Jet or SawStop, are usually fixed but sometimes move when the frame is jarred. Maintain wheel squareness for straight-ahead blade action. The blade’s position on the wheel is called “blade tracking“.
Blade Tracking Issues
The blade need to be riding up on the crown or top edge of the tire; not over, just up on the edge. Too low and the blade will sink down in the rim of the wheel and eventually become unseated. Most machines has an adjustment knob that holds the wheel housing.
You can use it to turn the machine on and loosen the tension. Then, work the knob until the blade rides up on center. Then gently push on the blade from side to side and it will remain centered.
If it moves, readjust until it stays put. You do this each time you change blades. Blades of different widths tracks differently.
Another biggie is worn/damaged tires. Over time bandsaw wheels with rubber tires gets cracked and harden. This creates a glazed surface that provide zero grip for holding the blade in place.
Worn and Damaged Tires
Examine your wheels carefully. If they’re cracked deeply or look shiny (glazed) from wear, change them out. Most wheel manufacturers (Woodstock, Grizzly, etc.) sell replacement tires.
Some tinkerers will use a duct-tape workaround: Wrap it around the tire for added traction. In a pinch, it’ll do. However, real tires would of give you better stability and support for clean cuts.
Lastly, inspect your bearings and blade guides. Guides that is too snug against the blade will cause friction, which in turn heats up the blade enough to warp it off the wheel. The guides should hover just behind the blade, touching it only when the blade deflects under load.
Blade Guide Inspection
Side blocks should be about a hair away from the blade. The thrust bearing need to be right back behind the cut. Proper guides makes the blades travel true and flat along the wheel.
This reduces blade stress. Tightening a loose bandsaw blade takes time and attention to detail. Get the tension right, make sure it tracks straight, align the blade, adjust your guides and tires.
All of those components affects one another. When everything balances out, you’ll have a smooth-running saw. No more running after blades, just cutting.
Well, that is what we are all looking for.