This could be a bit of a long shot but I would like to pick everyone's brains, especially those who had experience with correcting blade drift on a bandsaw. To give some context, I started my shop earlier this year and picked up a used WF Wells W-10-2 semi auto dual post bandsaw from a shop that was closing up shop. It is an old saw, but is still pretty solid. I got to see the saw cut in person but the owner told me I would need to replace the guide rollers and realign them if I wanted to do any amount of close or accurate cutting. Up until recently, I haven't really needed to do any accurate cutting as I have been able to feed bars on my CNC lathe and I can put the sloppy cut on the side with the remnant. However, I have a job coming up that will be machined from 3" steel bar and I cannot bar feed this material as it is a little too large for my spindle bore, so I will need to bandsaw cut them and chuck the blanks.
I set about tearing down and cleaning up the guides on the saw, replaced the rollers with new ones and did my initial adjustments checking the squareness of the blade to the table. The only thing I did not replace were the carbides on the guides as they appeared to be fine. The first few cuts I took with the saw seemed promising with only a small amount of noticeable taper in the blade feed direction, left and right were pretty square as well. I did these cuts with some scrap 1" round bar to give myself a baseline. As with any bandsaw, there is going to be a little blade drift due to the cutting forces involved, but on one properly set up it should be a consistent drift and shouldn't be very extreme. I decided since it was cutting well with the 1" bar, I would go up to a piece of 3" and test that out as well....This is where the problems start. When cutting the 3" bar, the cut starts out good until it gets about half way into the cut, at that point the blade starts to curve into the bar towards the clamp. The amount the blade drifts can be anywhere from .060" up to .200" at times and is not consistent from cut to cut. I tried to shim the guides to see if I could compensate for the drift, but all that ended up doing was creating a cut that was curved instead of just tapered. I should also mention that I was using a brand new Lenox blade for these tests and had the guides as close to the material to eliminate as much deflection as possible. I also played with the feed rate of the blade in the material and found that feeding it faster would make the blade taper more, but even slowing the feed down to almost nothing, it will still drift by an unpredictable amount. I went back to my 1 inch round bar to see if anything had changed, and it cut very consistently to the first test cuts with little to no taper at all. I also tried some square steel bar I had, and ended up with very little taper just like the smaller round bar.
I plan to contact WF Wells within the next week to see if I can solve this issue, but would anyone have any suggestions on something to try before I can get in touch with them? The part that has thrown me for a loop is the saw drifts very little, if at all when cutting small round bar or square/rectangular stock, but when I move up to the larger diameter stuff, it starts tapering off in a big way. This is a huge problem as I cannot set up a reliable machining process on the lathe if all of my slugs have tapered faces that need to be faced off. If I leave the saw as is and try to do this job, I will have to give myself at least an extra 1/4 of an inch more than I had planned for each slug to ensure that it gets cleaned up in the facing operations.
Thanks to anyone who can provide some advice.
