Bandsaw Table Installation and Alignment

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algale
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Re: Bandsaw Table Installation and Alignment

Post by algale »

paulrussell wrote: Mon Mar 01, 2021 11:23 am Not mentioned in this thread is that once a back-angled blade is fully engaged into the cut, the cutting load is slightly _more_ than a perpendicular blade. Pythagorean worked that all out for us. Admittedly, that penalty is slight given the shallow angle of the blade.
That's a very good point, Paul, and it adds to the doubts I have always harbored about the official explanation for the angle between the blade and the table. I do not believe for one minute the engineers at Shopsmith decided they needed blade tilt to prevent bogging and therefore went about building a band saw to accomplish this. Rather, I believe the blade tilt is an artifact of other deliberate design choices unique to the Shopsmith bandsaw, specifically how it autotracks by leaning the upper wheel backwards and using the autotrack bearing to prevent the blade from from falling off the back of the wheel. Those are desirable features, that an engineer would think about.

Of course the result of those choices is the blade tilts a small amount relative to the table and I suspect after getting questions about it, they decided to declare this was not only a normal condition from the design but a desirable "feature" and came up with the explanation that it helps prevent bogging down.
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Re: Bandsaw Table Installation and Alignment

Post by RFGuy »

algale wrote: Tue Mar 02, 2021 8:45 pm
paulrussell wrote: Mon Mar 01, 2021 11:23 am Not mentioned in this thread is that once a back-angled blade is fully engaged into the cut, the cutting load is slightly _more_ than a perpendicular blade. Pythagorean worked that all out for us. Admittedly, that penalty is slight given the shallow angle of the blade.
That's a very good point, Paul, and it adds to the doubts I have always harbored about the official explanation for the angle between the blade and the table. I do not believe for one minute the engineers at Shopsmith decided they needed blade tilt to prevent bogging and therefore went about building a band saw to accomplish this. Rather, I believe the blade tilt is an artifact of other deliberate design choices unique to the Shopsmith bandsaw, specifically how it autotracks by leaning the upper wheel backwards and using the autotrack bearing to prevent the blade from from falling off the back of the wheel. Those are desirable features, that an engineer would think about.

Of course the result of those choices is the blade tilts a small amount relative to the table and I suspect after getting questions about it, they decided to declare this was not only a normal condition from the design but a desirable "feature" and came up with the explanation that it helps prevent bogging down.
Interesting discussion...now I have to check my bandsaw to see if my blade is angled to the table or not. This explanation above makes the most sense to me for why Shopsmith chose this.
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dusty
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Re: Bandsaw Table Installation and Alignment

Post by dusty »

To get my table square to the blade I had to shim the front (infeed side) of the blade. Without doing that the upper surface of a work piece contacted the blade first. I don't know if this has any impact on the discussion but that is what my situation was.
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chapmanruss
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Re: Bandsaw Table Installation and Alignment

Post by chapmanruss »

Dusty,

You said
To get my table square to the blade I had to shim the front (infeed side) of the blade. Without doing that the upper surface of a work piece contacted the blade first.
I'm not sure if I am reading that correctly or if my understanding of it is off. If you had to shim the infeed side to get the blade to table angle to 90° than how was the upper surface of the work piece contacting the blade first before the adjustment? Wouldn't the bottom of the work piece contact the blade first without the shimming to 90°? That is what is happening with my 2006 Bandsaw without adding shims. I was checking the alignment on it yesterday but I haven't had the table off of it yet which is what I plan to do next. I am not sure it has the shim washers, as discussed before, between the table and the trunnions at all four bolting points.
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Re: Bandsaw Table Installation and Alignment

Post by edma194 »

Dusty, just checking here, before measuring the angle are you pushing the blade back with a piece of wood at the top until it hits the back bearing?
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dusty
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Re: Bandsaw Table Installation and Alignment

Post by dusty »

No I am not pushing a work piece into the blade. In fact, when doing this test the bandsaw is turned off.

Before I did any shimming
I was checking for square to the blade "on the back side of the blade". When I would bring a block of wood the top edge of the block would contact the blade and the bottom edge of the block was away from the blade. After leveling the table, the entire block would contact the blade simultaneouly.

Should have taken more pictures. :(
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chapmanruss
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Re: Bandsaw Table Installation and Alignment

Post by chapmanruss »

Thanks Dusty,

That is the way I thought it should be but the way you said it in the second sentence and following the first sentence
To get my table square to the blade I had to shim the front (infeed side) of the blade. Without doing that the upper surface of a work piece contacted the blade first.
had me wondering if you were feeding a work piece into the blade not checking the back side of the blade. Glad to have that cleared up.
Russ

Mark V completely upgraded to Mark 7
Mark V 520
All SPT's & 2 Power Stations
Model 10ER S/N R64000 first one I restored on bench w/ metal ends & retractable casters.
Has Speed Changer, 4E Jointer, Jig Saw with lamp, a complete set of original accessories & much more.
Model 10E S/N 1077 oldest one I have restored. 10E S/N 1033 & Mark 2 to be restored.
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chapmanruss
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Re: Bandsaw Table Installation and Alignment

Post by chapmanruss »

Yesterday afternoon I finished up maintenance on the 2006 Bandsaw. I really hadn't gone through it except replacing a couple of parts since I bought it a year ago with a Mark V since it has been an extra. I had the table off and it does have the four shim washers but one was not between the table and the trunnion on the infeed side. It was stacked with the thicker washer against the bolt head. Not sure what the previous owner was going for there but all are now in the proper place. I did not add extra shims to the infeed side to get the blade to table angle to 90° so it does have that slight "factory" angle. It does cut beautifully and made a perfect 90° cut on a piece of wool using the miter. :) It's now set up and ready to work.

I still have not decided if I will keep it or sell it but will wait until I check the alignments on the 1996 and 1956 Bandsaws and see if I want one set with the blade at 90° to the table. The 1956 shouldn't need any adjustments since it has hardly been used since it was restored less than a year ago but it has been 5 years since a full alignment was done on the 1996 Bandsaw when the Main Frame was replaced. My how time flies.

Thanks Dusty for inspiring me to do some alignment checks on my Bandsaws.
Russ

Mark V completely upgraded to Mark 7
Mark V 520
All SPT's & 2 Power Stations
Model 10ER S/N R64000 first one I restored on bench w/ metal ends & retractable casters.
Has Speed Changer, 4E Jointer, Jig Saw with lamp, a complete set of original accessories & much more.
Model 10E S/N 1077 oldest one I have restored. 10E S/N 1033 & Mark 2 to be restored.
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dusty
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Re: Bandsaw Table Installation and Alignment

Post by dusty »

I'm wondering, just wondering if the slight angle allows the saw dust to escape the gullets a little bit better than at 90 degrees.

There has to be a reason why the engineers did this. This is not just a happy coincidence. I find very little, if anything, that happened without justification. The Shopsmith design is well thought out. In my mind there is no room for criticism of the Shopsmith until you begin comparing it to a production or contractor tool.
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garys
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Re: Bandsaw Table Installation and Alignment

Post by garys »

My bandsaw is 40 years old this year so it has the cast iron table and no shims or washers of any kind under it. That would be the way it was assembled back in 1981.
My blade has a bit of angle as shown in this picture.
bansdaw.jpg
bansdaw.jpg (82.35 KiB) Viewed 205 times
I've used it only for resawing so I have not encountered any situations where that angle makes a difference. I don't use it for any scroll type work or cutting around corners. I have a scroll saw for that work. If I ever do any cutting of curves, I probably might shim the table to get it at 90 degrees.
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