Bandsaw Blade Tracking Adjustments Etc.

[algale]

So, I did several things.

First, I measured the upper wheel cant relative to the lower wheel using the method of putting a Wixey on the lower wheel axle, then on a straight edge across the lower wheel (establishing a zero reference) then against the upper wheel. I measured only about 0.6 degrees cant. This was irrespective of whether I measured it with a 1/4 inch blade tensioned or without tension. So my cant is less than what Dusty measured. But see post #122; with tension off there is additional slop and cant increase to 1.0 to1.1 degrees.

Second, I mounted my brand new never out of the package Shopsmith 5/8 inch blade on and tensioned it for 1/2 inch.

Third, I noticed (it was obvious) that the blade was clearly TWISTED just about as much as Caleb's BUT IN THE OPPOSITE DIRECTION!!!!! See post #122; actual measurement of the twist shows it is only 3 degrees, so not as dramatic as 20 degrees that Caleb reports.

To see whether this created a practical problem for re-sawing, I took a piece of scrap wood and marked the mid line, powered up the headstock and cut down the line by eye about half way to establish the "drift." Then I turned off the band saw and clamped a longer piece of scrap against the piece already cut and clamped it to the table to establish a fence (I don't own a fence) and cut some more scrap. The blade cut straight and true -- just not remotely parallel to the markings on the table.

What to make of this? Well, I plan on making a drift-adjustable band saw fence this weekend.

[JPG]

I have been 'missing' today and have one concern. Bill Mayo does not recommend the push pull approach to establishing the cant. He prefers to apply pressure to the axle since the wheel push pull can also warp the wheel. I tend to agree with him although I have not to my knowledge warped a wheel when pushing pulling.

I am not totally sure of my wheel taper statements when the tires are included and that both wheels are the same.

I do not think 4 degrees is accurate. My straight edge pix above show a 1/8" tilt over 11"(1/4" - 1/8" spacing) which is where my .6 degrees figure came from.

The rim bevel is about a 6 degree angle(3/32 over 7/8")[using Dusty's measurements of diameters].

These 'conclusions' do not support my current 'understanding'. Further work/thinking/measuring is indicated.

[algale]

So I went back down to the shop to retest my observations regarding wheel cant (tilt) and blade twist with the Shopsmith 5/8ths blade.

With the tension set properly, I still measure about 0.6 degrees cant (tilt) of the upper wheel relative to the lower wheel.

However, with tension off, there is additional slop in the upper wheel and if gentle pressure is applied, the maximum measurable cant increases to 1.0 to 1.1 degrees, which is consistent with what Dusty observed but a heck of lot less than the 4 degrees of cant (sounds like a new internet game, kind of like 4 Degrees of Separation) that Shopsmith Customer Service told Caleb.

Now, as for blade twist. The blade clearly is twisted with the teeth pointing to the operator's left (opposite direction of twist to what Caleb observed). But, the twist is not as dramatic as I thought. I am measuring 3 degrees of twist. I tensioned/detension the blade several times and spun the wheels and each time measured 3 degrees of twist.

Caleb, have you measured the twist or are you just eyeballing it at 20 degrees? Put your miter gauge in the miter slot on the band slaw table. Put the base of your engineer's square against the face of the miter gauge, loosen the lock knob on the miter gauge and adjust the miter gauge until the blade of the square is flush to the band saw blade (avoid measuring off of a tooth). You may need to clamp an auxiliary fence to the miter gauge to get your square close enough to the blade. You can then get a reading right off the miter gauge's protractor.

[JPG]

After squinting, thinking etc. I have come to the following 'conclusions' that support my understanding of the uniqueness of the SS band saw wheels.

The upper wheel is canted about 0.6 degrees from vertical(the axle is canted from horizontal). The top back of the wheel 'leans' toward the casting(away from the cover). That angle is the only measurement that I have reason to believe is fairly accurate. It is based upon the difference between the rim measurement at the top and bottom of the upper wheel from the edge of a straight edge positioned against the rim of the bottom wheel that contacts both the top and bottom of the rim. That difference is about 1/8". The rim has an 11" diameter. .125 / 11 = .01136 asin(.01136) = .651°.

The wheels have a larger rim od on the back side, but that is to provide a 'stop' for the positioning of the tire on the wheel.

The tires are slightly beveled with a larger od at the back.

The lower wheel tire is beveled more than the upper wheel tire.

I do not want to speculate on the bevel angle since I have no way to accurately measure it.

The following is my speculation as to how it is all 'supposed' to be(no numbers/angles etc.)

The upper wheel is canted(about 0.6°) with the top back of the wheel leaning towards the casting(away from the cover).

The lower wheel axle is horizontal as would be expected since it is the 'driver'.

The lower wheel tire is beveled slightly and I believe it is intended to be approximately equal to the cant angle of the upper wheel when compressed under blade tension.

The upper wheel tire is also beveled, but appears to be a smaller angle than the lower wheel tire. I believe that is to allow for the upper wheel cant.

Although I have little faith in my measuring the tire bevel angle, it appears to be close to 4°. That coincides with SS info given today assuming that was the angle being referred to. That also makes me believe tire compression under tension is part of the confusion. I think the back edge of the blade is under greater tension than the cutting edge because of the tire bevel(od is greater on that 'side').

FWIW the upper(rear) guide bearing places the back of the blade about 1/8" from the back edge of the upper wheel tire and the lower guide bearing does the same at the lower wheel tire.

[algale]

After squinting, thinking etc. I have come to the following 'conclusions' that support my understanding of the uniqueness of the SS band saw wheels.

The upper wheel is canted about 0.6 degrees from vertical(the axle is canted from horizontal). The top back of the wheel 'leans' toward the casting(away from the cover). That angle is the only measurement that I have reason to believe is fairly accurate. It is based upon the difference between the rim measurement at the top and bottom of the upper wheel from the edge of a straight edge positioned against the rim of the bottom wheel that contacts both the top and bottom of the rim. That difference is about 1/8". The rim has an 11" diameter. .125 / 11 = .01136 asin(.01136) = .651&#176]are [/B]slightly beveled with a larger od at the back.

The lower wheel tire is beveled more than the upper wheel tire.

I do not want to speculate on the bevel angle since I have no way to accurately measure it.

The following is my speculation as to how it is all 'supposed' to be(no numbers/angles etc.)

The upper wheel is canted(about 0.6°) with the top back of the wheel leaning towards the casting(away from the cover).

The lower wheel axle is horizontal as would be expected since it is the 'driver'.

The lower wheel tire is beveled slightly and I believe it is intended to be approximately equal to the cant angle of the upper wheel when compressed under blade tension.

The upper wheel tire is also beveled, but appears to be a smaller angle than the lower wheel tire. I believe that is to allow for the upper wheel cant.

Although I have little faith in my measuring the tire bevel angle, it appears to be close to 4°. That coincides with SS info given today assuming that was the angle being referred to. That also makes me believe tire compression under tension is part of the confusion. I think the back edge of the blade is under greater tension than the cutting edge because of the tire bevel(od is greater on that 'side').

FWIW the upper(rear) guide bearing places the back of the blade about 1/8" from the back edge of the upper wheel tire and the lower guide bearing does the same at the lower wheel tire.

Your hypothesis that the tires have a front/rear and upper/lower orientation is not consistent with my recent tire replacement. The urethane replacement tires were uniform in thickness and there was no marking to indicate which tire was for the upper versus lower wheel or which edge was the front/rear of either tire. Nothing in the instructions indicated the tires had to be oriented in a particular way or used on a particular wheel.

When I removed my rubber tires, moreover, I noticed no difference in thickness, either front to back or from upper to lower wheel except where the blade had compressed the tire. Since the blade never rides all the way back on the tire, this leave the back of the tire a little thicker than the rest, but I do not believe the tire comes this way from Shopsmith. Any one done a rubber tire replacement remember whether the replacement rubber tires came with directions for front/rear or upper/lower?

I agree that the rim variance on the wheels is to provide a stop for the tires. That is what I was trying to describe. The area between the larger rear shoulder and the smaller front shoulder where the tire sits is flat.

[dusty]

So, I did several things.

First, I measured the upper wheel cant relative to the lower wheel using the method of putting a Wixey on the lower wheel axle, then on a straight edge across the lower wheel (establishing a zero reference) then against the upper wheel. I measured only about 0.6 degrees cant. This was irrespective of whether I measured it with a 1/4 inch blade tensioned or without tension. So my cant is less than what Dusty measured. But see post #122]

Second, I mounted my brand new never out of the package Shopsmith 5/8 inch blade on and tensioned it for 1/2 inch.

Third, I noticed (it was obvious) that the blade was clearly TWISTED just about as much as Caleb's BUT IN THE OPPOSITE DIRECTION!!!!! See post #122; actual measurement of the twist shows it is only 3 degrees, so not as dramatic as 20 degrees that Caleb reports.

To see whether this created a practical problem for re-sawing, I took a piece of scrap wood and marked the mid line, powered up the headstock and cut down the line by eye about half way to establish the "drift." Then I turned off the band saw and clamped a longer piece of scrap against the piece already cut and clamped it to the table to establish a fence (I don't own a fence) and cut some more scrap. The blade cut straight and true -- just not remotely parallel to the markings on the table.

What to make of this? Well, I plan on making a drift-adjustable band saw fence this weekend.

Are you reporting a twist exists in a tensioned blade (with guides and cool blocks in place)?

[algale]

Are you reporting a twist exists in a tensioned blade (with guides and cool blocks in place)?

The short answer to your question is "Yes." The long answer is that my initial observations were taken with the 5/8ths inch blade properly tensioned and properly tracking against the upper autotrack bearing and properly tracking against the lower blade guide bearing. The blade was not in contact with the upper blade guide bearing (except intermittently at the weld). Furthermore, I snugged the cool blocks up against the blade and brought them about as far forward as possible.

However, I quantified the angle of the twist at 3 degrees with the cool blocks fully backed off because I didn't want them influencing my measurement.

[dusty]

The short answer to your question is "Yes." The long answer is that my initial observations were taken with the 5/8ths inch blade properly tensioned and properly tracking against the upper autotrack bearing and properly tracking against the lower blade guide bearing. The blade was not in contact with the upper blade guide bearing (except intermittently at the weld). Furthermore, I snugged the cool blocks up against the blade and brought them about as far forward as possible.

However, I quantified the angle of the twist at 3 degrees with the cool blocks fully backed off because I didn't want them influencing my measurement.

Three degrees is not very much so I may have the same twist and have never noticed it. Remember, the cool blocks are there for a purpose and maybe this is it. This could also be the reason why you lower the guides down close to the work. When set up properly for a cut, there is very little separation between upper and lower cool blocks.

Hmmm. Ya think?

I really don't think I have that sort of twist with the 5/8" blade but I'll look.

The following show my "twist" when not tensioned and then when tensioned. Alignment is different as indicated by the grooves in the table. But I can change that by moving the table. I'm going to leave it alone for now.


[ATTACH]20648[/ATTACH]
No blade tension at all.

[ATTACH]20649[/ATTACH]
Blade fully tensioned.

[JPG]

Your hypothesis that the tires have a front/rear and upper/lower orientation is not consistent with my recent tire replacement. The urethane replacement tires were uniform in thickness and there was no marking to indicate which tire was for the upper versus lower wheel or which edge was the front/rear of either tire. Nothing in the instructions indicated the tires had to be oriented in a particular way or used on a particular wheel.

When I removed my rubber tires, moreover, I noticed no difference in thickness, either front to back or from upper to lower wheel except where the blade had compressed the tire. Since the blade never rides all the way back on the tire, this leave the back of the tire a little thicker than the rest, but I do not believe the tire comes this way from Shopsmith. Any one done a rubber tire replacement remember whether the replacement rubber tires came with directions for front/rear or upper/lower?

I agree that the rim variance on the wheels is to provide a stop for the tires. That is what I was trying to describe. The area between the larger rear shoulder and the smaller front shoulder where the tire sits is flat.

I agree that there is no appreciable taper to the tires except a slight 'thickening' at the rear where a blade has never resided. The 'effective' taper is due I think to tensioning.(much conjecture here) The cant of the upper wheel pulls the blade 'axis of rotation' away from horizontal. When tension is added, the lower tire will be compressed more at the back of the blade. A similar but opposite compressing takes place on the upper tire. This compression of the tires allows the wheels to be rotating in non-parallel axis(s).

I have not measured the resultant blade angle deviation from 'vertical', but I would expect it to be less than the 0.6° wheel angle.

[algale]

I agree that there is no appreciable taper to the tires except a slight 'thickening' at the rear where a blade has never resided. The 'effective' taper is due I think to tensioning.(much conjecture here) The cant of the upper wheel pulls the blade 'axis of rotation' away from horizontal. When tension is added, the lower tire will be compressed more at the back of the blade. A similar but opposite compressing takes place on the upper tire. This compression of the tires allows the wheels to be rotating in non-parallel axis(s).

I have not measured the resultant blade angle deviation from 'vertical', but I would expect it to be less than the 0.6° wheel angle.

I think you are right that the tensioning the blade compresses the tire under the blade. I would add that if the blade is left under tension for a long period of time, the tire may take a set. My old rubber tires had a set to them where a 1/4 inch blade had been left under tension for years by the PO.