Bandsaw Blade Tracking Adjustments Etc.

caleb · Post by **caleb** » Mon Mar 18, 2013 1:17 pm

JPG40504 wrote:An important 'detail' not mentioned is the beveled rims. Both wheels have a larger diameter on the back side. That angle is approximately 0.6 degrees.*

Now consider the lower wheel. In order for the blade to track flatly on the lower wheel, the blade 'axis of rotation' must be tilted from vertical the same amount. In order for the blade to also track flatly on the upper wheel, the wheel must have the same bevel, but also must be positioned slightly towards the rear and tilted(canted).

I conclude the twisting is caused by insufficient canting of the upper wheel which would position the back of the blade at the lower wheel too far 'back' to ride smoothly on the lower guide bearing.

The effective cant is reduced when tension is applied and that is why I think the bearing is 'sloppy' .

*I am not sure the bevel is the same on both wheels. I tentatively believe the upper wheel bevel must be twice the lower wheel bevel for this to work. The .6 degree angle is I believe the upper wheel axle 'cant' from horizontal.

From What I am seeing on the lower wheel I agree with jpg40504, When I removed the upper and lower blade guide bearings and rotated the blade wheels, the blade untwisted and moved to be exactly aligned with the back edge of the lower wheel and perfectly straight, (non twist) so this leads me to believe that the canter is way off and causing the blade to put a large amount of pressure on the lower blade guide bearing.
When I removed the lower blade guide bearing and spun the wheels the blade moved back in the guides so much that it now rested completely on the upper blade guide bearing and then twisted in the opposite direction.
then I removed the upper blade guide bearing back the cool block mounts all the way back and the blade came straight. and was then moved toward the center of the upper wheel by about another 1/16 and it was hard up against the lower wheel edge.

this all follows what you guys have been so helpful in figuring out.
personally I think that ss should put you all on the payroll as resident genius's. like the geek squad or genius bar at apple.

Thank you so much and for going so far with me and being patient with my bad descriptions.

Caleb

dusty · Post by **dusty** » Mon Mar 18, 2013 1:23 pm

caleb wrote:From What I am seeing on the lower wheel I agree with jpg40504, When I removed the upper and lower blade guide bearings and rotated the blade wheels, the blade untwisted and moved to be exactly aligned with the back edge of the lower wheel and perfectly straight, (non twist) so this leads me to believe that the canter is way off and causing the blade to put a large amount of pressure on the lower blade guide bearing.
When I removed the lower blade guide bearing and spun the wheels the blade moved back in the guides so much that it now rested completely on the upper blade guide bearing and then twisted in the opposite direction.
then I removed the upper blade guide bearing back the cool block mounts all the way back and the blade came straight. and was then moved toward the center of the upper wheel by about another 1/16 and it was hard up against the lower wheel edge.

this all follows what you guys have been so helpful in figuring out.
personally I think that ss should put you all on the payroll as resident genius's. like the geek squad or genius bar at apple.

Thank you so much and for going so far with me and being patient with my bad descriptions.

Caleb

I believe I speak for everyone on the forum who participates in these dissertations. We do this not just for you but for ourselves as well. I know that every time I get involved, I learn a great dea bot from others and from my own research and study.

At any rate, you are welcome and I hope this really helps to solve this mystery.

algale · Post by **algale** » Mon Mar 18, 2013 1:28 pm

dusty wrote:OKAY. I must plead ignorance here. I have never seen the wheels with the tires removed. If there is a depression in the edge of the wheel where the tire rests, I cannot detect that.

After my previous post I did reexamine the wheels and the rim of my wheels (front and back) are not the same thickness.

The diameter of the wheel (excluding tires) on the front side is 10 25/32" while one the rear side the diameter is 10 31/32".

The diameters (including the tires) is 11 3/32" on both sides.

The more I look - the less I know.

Don't know whether to call it a depression where the tire sits or a shoulder/rim that stands proud above where the tire sits.

Those shoulders/rims are not the same. The back shoulder/rim is wider and taller than the front. I believe the difference in your measurements is probably the shoulder/rim height variance (since it obviously is not a measurement of the actual surface that the tire is presently sitting on).

caleb · Post by **caleb** » Mon Mar 18, 2013 2:18 pm

Ok so the word from SS is to first check the tension setting scale to make sure it is aligned properly, then put a 1/4 blade on and spin by hand and make sure it is setting in the correct location on the wheel. loosen off the tension then put the palm of one hand on the top edge of the upper wheel and grab the bottom edge and gently rock the wheel until it bends a little
then re tension and check where the blade rides. rinse and repeat until the 1/4 blade is in the correct location on the wheel 1/8 from the top.

but here is my query. if you do this with the upper and lower blade guide bearings installed, then you won't get a true read of where the blade wants to ride. you will only see where it is riding now and you won't see how much pressure is being applied to the lower blade guide bearing.

So I am going to modify their directions remove the lower and upper blade guide bearings then see where the 1/4 blade rides as this will give a more accurate reading of where the blade actually wants to ride, leaving it on will only tell you where the lower blade guide bearing is set which really won't do anything to a 1/4 blade because the are much stronger twist wise that the 5/8.

I think this is an important step in getting the cant correct, my understanding is that the backup guide bearings (upper and lower) are primarily there to give support to the blade during cutting not to govern the blade tracking. that is what the auto track bearing is for.

What do you guys think?

Caleb

algale · Post by **algale** » Mon Mar 18, 2013 3:05 pm

I think I'd follow Shopsmith's recommended procedure. You can back off the upper back up bearing but I'd leave the lower back-up bearing. It is supposed to be in contact with the blade 100% of the time as is the autotrack bearing.

beeg · Post by **beeg** » Mon Mar 18, 2013 3:35 pm

WHO did ya talk to at SS? I think I'd go with THEIR advice and knot change it. Since those two women have about 125000 hours helping people with a MarkV.

dusty · Post by **dusty** » Mon Mar 18, 2013 3:35 pm

The Tracking Bearing, on the left hand side, positions the blade as it comes off the lower wheel (before it engages the upper wheel). The lower bearing on the right hand side serves the same purpose. It positions the blade as it comes off the upper wheel and before it contacts the lower wheel.

If you run with both bearings removed (no contact with the blade)), only the auto-track bearing and the existing cant position the blade. We pretty much know that the tracking bearing is in the right position but what about the cant.

If the cant is improper, and some think it is, without the bearing on the right hand side - who knows what is going to happen.

If you are going to do this, spin the wheels by hand. Do Not power rotate until you are certain that the blade is going to remain on the wheels.

I don't know who you spoke with at Shopsmith but I doubt some of their instructions. I at least believe that they will lead you right back into the vicious circle that we have been running in.

You have been using a 5/8" or 1/2" blade. Proper tension is about all the tension you can achieve on this bandsaw. Over tension is certainly not your problem and under tension (if you have been tensioning at all) is not likely to be your problem.

You have been setting tension - correct??

With regard to your last statement. The upper backup bearing, if adjusted according to Shopsmith instructions, only comes into play when feeding stock into the blade. The lower backup bearing is in contact, if adjusted according to Shopsmith instructions, is in contact with the blade at all times.

As I stated above, bearings on both sides serve to limit the backward motion of the blade thus serve to "jointing" control tracking.

saminmn · Post by **saminmn** » Mon Mar 18, 2013 3:54 pm

algale wrote:I think I'd follow Shopsmith's recommended procedure. You can back off the upper back up bearing but I'd leave the lower back-up bearing. It is supposed to be in contact with the blade 100% of the time as is the auto-track bearing.

+1 The above. If I understand it correctly, the lower bearing is a part of the SS band saw auto-track idea.

caleb · Post by **caleb** » Mon Mar 18, 2013 5:21 pm

Ok so after checking everything and woops adjusting the upper wheel to be in the right place I noticed that I hadn't put the lower backup bearing back in which once done messed up the upper wheel. So I replaced the lower bearing and re-did the adjustments. with the 1/4 blade everything looked as good as it did before when I tested with the 1/4 blade. so I then put the 5/8 blade back on and hand rotated it and low and behold the twist came right back.

Tension question... yes I am setting it a 1/2 for the 5/8 blade.

so after following SS instructions the cant should be bang on. the spacing on the wheels is bang on. and was before I started bending the upper arm around as directed. I have been talking to Linda from SS and she has given me great advise. there was one mistake which she double checked and then agreed with me, it was a slip it happens to everyone and she self corrected.

but I think I must have spoken with Doug at some stage. I totally forgot about that and if you are on here I am so sorry for creating double work for everyone. I asked about the degree of cant and linda thinks that it is approx 4 degrees, so if you guys are seeing 6 I would say that is about correct.

I think I am going to buy some more blades from woodcraft and send my 5/8 blade back to ss for testing.

Thanks again

If there are anymore pics or videos I can send you guys please let me know.

Caleb

dusty · Post by **dusty** » Mon Mar 18, 2013 5:33 pm

caleb wrote: So I am going to modify their directions remove the lower and upper blade guide bearings then see where the 1/4 blade rides as this will give a more accurate reading of where the blade actually wants to ride, leaving it on will only tell you where the lower blade guide bearing is set which really won't do anything to a 1/4 blade because the are much stronger twist wise that the 5/8.
Caleb

I'm thinking on this but I am not using a 5/8" Shopsmith blade. I use the 5/8" when resawing and I use something other than a Shopsmith blade for that.