Bandsawn Circles Won’t Close?

Bandsawn Circles Won’t Close?

I have a 9-in. RYOBI band saw, about three years old, that I want to use to cut some circle shapes. I built a dovetailed jig that allows me to make circles from 4 to 18 in. in diameter. I have the front of the 1/8-in.-wide saw blade tracking in the middle of the drive wheel and the back bearing barely touching the blade. When I cut my circle, the end point drifts about 1/4 in. away from the starting point. I have tried cutting really slowly with frequent backing up, but I cannot get it any closer than the 1/4-in. offset. Both top and bottom side bearings are about 1/8-in. away from the blade. The bearings can’t be moved any closer to the blade. Any suggestions as to what I should do to get the circle to close? – Wim Wijnberg

Tim Inman: The tracking point is your issue, I think. On my circle cutter jig for my band saw, it works best when the tip of the cutting tooth is in contact with the arc/line I want to follow for the cut. When my blade is set to track from the midway point of the blade, it “leads” as you are describing. Work with test cuts and set the jig to track at the tooth points, and I think you’ll have it. I like to set the tracking by moving my jig instead of moving the blade on the wheels. That way, when I’m done with the circle-cutting job, nothing on my saw has to be reset for other work.

Chris Marshall: If the side bearings on the upper and lower blade guides can’t be brought closer to the blade than 1/8 in., I think the problem is actually a twisting blade. Those side blade guide supports should be set so close to the blade that they almost touch it during straight cuts and actually do touch it when cutting curves. Their purpose is to keep the blade tracking straight. As you turn the workpieces to cut your circles, the blade is deflecting in the kerf and drifting off-course because there’s nothing to prevent it from twisting. You might be able to reduce the deflection by putting more tension on the blade, but the bigger problem is that those side bearings are basically offering no lateral support. Unfortunately, on an entry-level band saw like you have (not being critical here but only making an observation), there’s almost surely no aftermarket replacement blade guides to improve the saw’s performance.

Are you certain the blade guides are installed correctly? Any chance the shafts that hold the bearings in place on the guides could be reversed, and the bearings re-mounted, to offer more reach? I’m surprised that RYOBI doesn’t offer closer side bearing-to-blade tolerances, because it’s a basic tuning requirement for any band saw. Checking the online PDF manual for the current 9-in. RYOBI Band Saw shown above, I found that you can adjust those blade guides to within acceptable tolerances next to the blade. So again, I wonder if the blade guides on your machine are assembled properly?

Here’s another idea: you might be able to purchase bearings with larger outside diameters to eliminate the gaps alongside the blade. A source such as McMaster-Carr® might have just what you need for a reasonable cost. But first, I would double-check that your blade guides are put together properly.

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