Bandsaw Blade Tracking Adjustments Etc.

[algale]

This entire thread has been very interesting and has caused me to think a lot about how the band saw really works to maintain proper tracking. I understand the function of the back up bearings. It is why(how) these guide bearings even come into play that has me puzzled.

Cant or canter. This seems to be the issue.

cant 1 (knt)n.1. Angular deviation from a vertical or horizontal plane or surface]2. [/B] A slanted or oblique surface.
3. a. A thrust or motion that tilts something.
b. The tilt caused by such a thrust or motion.

4. An outer corner, as of a building.

v. cant·ed, cant·ing, cants
v.tr.1. To set at an oblique angle; tilt.
2. To give a slanting edge to; bevel.
3. To change the direction of suddenly.

v.intr.1. To lean to one side; slant.
2. To take an oblique direction or course; swing around, as a ship.

OKAY.

So what? What is at an angle and to what reference?

Are the shafts of the two bandsaw wheels suppose to be parallel to one another or is this where the canter comes into play?

OR

Is the upper bandsaw wheel suppose to be canted with respect to the shaft? That does not seem likely (at least not to me). It seems to me that that would result in wobble.

Here is a sketch of what I think a canted upper bandsaw wheel is. However, ion this sketch the wheel is canted the WRONG way. The blade would tend to run right off the upper wheel.

[ATTACH]20639[/ATTACH]

Note that the two shafts are not parallel to one another. Is this the way it is done in the Shopsmith Bandsaw?

Dusty,

In theory (because I haven't done it) I think a measurement of the relative angles of the upper and lower axles could be accurately taken using a Wixey or similar device. AIUI, the lower axle extends through the band saw and is used to drive the band saw (off of the headstock/power station, etc.) So one could take a measurement of the angle of the lower axle on the back side of the band saw (after removing the coupler). As for the upper axle, one would have to pop off the C-clip and washer and remove the upper wheel and take a measurement. That would give you your answer, again in theory. Whether the relative angles are consistent from band saw to band saw (Shopsmith version only) would require the measurement of several samples.

And if the axles are not parallel, as I suspect, changing the bearings won't do a thing for Caleb.

Al

[dusty]

Dusty,

In theory (because I haven't done it) I think a measurement of the relative angles of the upper and lower axles could be accurately taken using a Wixey or similar device. AIUI, the lower axle extends through the band saw and is used to drive the band saw (off of the headstock/power station, etc.) So one could take a measurement of the angle of the lower axle on the back side of the band saw (after removing the coupler). As for the upper axle, one would have to pop off the C-clip and washer and remove the upper wheel and take a measurement. That would give you your answer, again in theory. Whether the relative angles are consistent from band saw to band saw (Shopsmith version only) would require the measurement of several samples.

And if the axles are not parallel, as I suspect, changing the bearings won't do a thing for Caleb.

Al

I have (just this moment) done exactly as you describe. Using the Wixey on the lower axle (on the backside of the bandsaw), I established a "reference surface".

With a straight edge across the lower bandsaw wheel, I took an angular measurement of the lower bandsaw wheel. It is at 90° to the shaft.

Repeating that same measurement on the upper wheel I find it to be 88.9° canted inward at the top. The two shafts are NOT parallel. Where is this difference introduced? I think the answer is pictured in post #76 of this thread. The Upper Wheel Arm and Axle (#19 in the Bandsaw Exploded Parts View) in conjunction with the way that part is mounted to the Bandsaw Housing I believe introduces the canter.

It is not designed to be adjustable but ........

and I am even more convinced that changing bearings will accomplish nothing except maybe a quieter upper wheel.

This axle, BTW, seems to be canted in more than one direction. I can not explain but a visual inspection will reveal that. This statement is questionable if not outright wrong!!! It now appears to me to be an optical illusion.

If I just had a bandsaw that I did not want to keep in operating condition I would go further (or farther) with this. I have already dismantled some to get to this point but no further.

[algale]

I have (just this moment) done exactly as you describe. Using the Wixey on the lower axle (on the backside of the bandsaw), I established a "reference surface".

With a straight edge across the lower bandsaw wheel, I took an angular measurement of the lower bandsaw wheel. It is at 90° to the shaft.

Repeating that same measurement on the upper wheel I find it to be 88.9° canted inward at the top. The two shafts are NOT parallel. Where is this difference introduced? I think the answer is pictured in post #76 of this thread. The Upper Wheel Arm and Axle (#19 in the Bandsaw Exploded Parts View) in conjunction with the way that part is mounted to the Bandsaw Housing I believe introduces the canter.

It is not designed to be adjustable but ........

Did you take the upper measurement off of the upper wheel or off of the upper axle or both?

If you took the upper measurement off of the upper axle alone is there additional "slop" built into the upper wheel needle bearings that allows the wheel additional tilt/cant when under tension?

I will try to take measurements off of my band saw later so we have at least 2 points of reference. Maybe others will help build a sample pool from which we could draw some conclusions about how much cant there should be. I'll bet there's an engineer at Shopsmith who knows what the specification for the wheel/axle cant should be.

Al

[JPG]

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.

[dusty]

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.

Everything you say is relevant if "tracking position" is the issue. At this point, all I am trying to do is understand how the two wheels relate to one another and where the cant is actually created.

All that I have concluded is that the axles of both wheels are perpendicular to a plane established by the wheels.

[dusty]

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.

Maybe I did not spend enough time looking and evaluating the wheels but I do not see the bevel that you say exists. I assume you are speaking of the outer circumference of the wheels with the tires in place.

Except for the indentures created by the blades, my tires are flat and appear to be perpendicular to the plane of the wheels circumference.

A 0.6° bevel will be hard to ascertain without some instrumentation.

[algale]

Maybe I did not spend enough time looking and evaluating the wheels but I do not see the bevel that you say exists. I assume you are speaking of the outer circumference of the wheels with the tires in place.

Except for the indentures created by the blades, my tires are flat and appear to be perpendicular to the plane of the wheels circumference.

A 0.6° bevel will be hard to ascertain without some instrumentation.

I recently removed my rubber tires and replaced with the urethane. While I wasn't looking for it, I also did not notice a bevel to the surface where the tire sits. But I also agree that a 0.6 degree bevel would be virtually imperceptible to the eye. Now, if we are talking about the rims/shoulders that keep the tire in/on, it is true that the back rim/shoulder is both wider and taller than the front rim/shoulder. But the space between where the tire sits appeared flat to my eye.

[dusty]

I recently removed my rubber tires and replaced with the urethane. While I wasn't looking for it, I also did not notice a bevel to the surface where the tire sits. But I also agree that a 0.6 degree bevel would be virtually imperceptible to the eye. Now, if we are talking about the rims/shoulders that keep the tire in/on, it is true that the back rim/shoulder is both wider and taller than the front rim/shoulder. But the space between where the tire sits appeared flat to my eye.

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.

[caleb]

Did you take the upper measurement off of the upper wheel or off of the upper axle or both?

If you took the upper measurement off of the upper axle alone is there additional "slop" built into the upper wheel needle bearings that allows the wheel additional tilt/cant when under tension?

I will try to take measurements off of my band saw later so we have at least 2 points of reference. Maybe others will help build a sample pool from which we could draw some conclusions about how much cant there should be. I'll bet there's an engineer at Shopsmith who knows what the specification for the wheel/axle cant should be.

Al

I will ask when I talk to them today.

[dusty]

Did you take the upper measurement off of the upper wheel or off of the upper axle or both?

If you took the upper measurement off of the upper axle alone is there additional "slop" built into the upper wheel needle bearings that allows the wheel additional tilt/cant when under tension?

I will try to take measurements off of my band saw later so we have at least 2 points of reference. Maybe others will help build a sample pool from which we could draw some conclusions about how much cant there should be. I'll bet there's an engineer at Shopsmith who knows what the specification for the wheel/axle cant should be.

Al

I don't doubt that there is someone there who either knows or could find out but I am not sure you will get anyone to commit to a specific number. Since it is not adjustable, that is probably not a number that anyone in production is concerned about and engineering won't discuss.

Is it discussed anywhere in the manual?? I don't believe so!