I have recently purchased an older (green) Jet 20 inch bandsaw and have started reconditioning it. (An absolutely awsome saw, but that is another story). Basicly I am replacing some worn belts and tires, as well as cleaning and aligning it, etc. I have Mark Duginske's book and have been following the advice in the book, but the book has raised some questions.
After testing the coplanerity of the saw I found the the upper wheel was slightly behind the lower wheel. This is a condition which Duginske says is common and can be corrected with a spacer washer behind the bearing on the upper wheel. I agree that this non-coplanarity is common, since I have seen it in other bandsaws such as my very cheep 14 inch clone. But, why does it always seems to be in the same direction with the upper wheel being further back than the lower wheel? That coincidence seems odd enough to me that I wonder if the saw manufacturers have have been doing it for some unknown reason.
Does anyone know if bandsaw manufacturers purposely build in this kind of offset into the alignment on purpose? If it is easy to adjust, why is it so common in saws and mostly in the same direction? What kind of advantage could it have? The blade tention does not seem capable of warping the wheels in this manner. This saw even has adjustments for tuning the position of the wheels, but they seem to have been purposely aligned with the wheels very parallel, but offset in depth.
I will probably try running the saw both as it is and with the wheels fully coplaner once I have the tires replaced and the saw put back together so I can see how much of a difference there is. However, I doubt I am experienced enough to notice much of a difference, and was wondering if anyone knew more about this common irregularity.
Inquireing minds want to know.