Bandsaw: tracking and drift and the snodgrass method

[John TenEyck]

Did you bother to put a straight edge across the two wheels before or after you removed the shim? If removing the shim helped the blade cut straight that's great, but to say the wheels don't need to be coplaner with no proof is poor journalism. As Phil said, you could just as easily have brought them closer to being in plane. All I know is my saw would not cut straight, and by straight I mean parallel with the miter slot, until after I aligned the wheels to be as close to coplaner as I could get them. BTW, that required adding shims behind the upper wheel. That is with no blade installed. Under tension the upper wheel has to be tilted back to accommodate the bending of the frame. When the blade rides in the center of the top wheel it's closer to the front on the bottom wheel, at least on my saw. The blade is perpendicular to the table so that tells me the upper frame is bending towards the front of the saw. Other saws may behave differently but the alignment principles are the same - there's no myth about it.

John

[Bob Wingard]

You understand the logical consequence of your statement would be either:

(1) There is some ideal other than coplanar and saw wheels must be thusly aligned.

-or-

(2) Bandsaws work great provided the wheels are NOT coplanar.


#1 is unlikely, otherwise the relationship between the two wheels would have been published by a manufacturer somewhere along the line.

#2 is unlikely, as so many people have found that their saws work better as the wheels approximate a coplanar relationship.

So based on this, it seems likely that at some point you added the shim and actually moved your wheels out of alignment. Removing the shim brought them back.

Coplanar was a poor choice of words to explain that wheels should be aligned to induce the least amount of twist to a blade revolving around them. There is, of course, a point of diminishing returns here. But twist = vibration, and the more closely aligned the wheels, the less twist.

#1 : Coplanarity simply does not exist ... at least, it cannot be maintained. Change a blade .. change tension .. adjust the blade's tracking .. it's GONE !!!

#2 : IF you could achieve the elusive coplanarity, tracking the blade would become extremely difficult ... the closer you come to being coplanar, the more it resembles trying to balance an elephant on the edge of a knife blade ... the slightest nudge either way, and the tracking jumps to one side or the other.

#3 : If you need to shim the upper wheel whilst attempting the coplanarity exercise, for every tiny fraction of an inch you move the wheel outward, you are substantially increasing the load on the tracking/tensioning components of the saw ... a longer moment of force means you are actually losing leverage the further you place the wheel from it's horizontal pivot point ... and you might possibly be exceeding the manufacturer's recommended loading on those components.

#4 : Your claim that the manufacturers should/must claim some mystical relationship between the wheels is simply nonsense ... THEY have engineered their products to work a certain way, under specific conditions ... there is simply no need to mess with their engineering.

#5 : You ARE correct in that at some point I inserted the shim, trying to attain the mythical coplanarity ... when I realized what an utter waste of time that was, I simply removed it .. returning the saw to it's original factory configuration, at which time, it performed flawlessly using Alex's technique.

#6 : Any blade, tensioned between two wheels should not have any "twist" in it ... such a condition could only occur when there is an extreme horizontal misalignment of the two axis.

[Bob Wingard]

Did you bother to put a straight edge across the two wheels before or after you removed the shim?
John

NAH ... I just randomly turned and surface ground a chunk of steel to some arbitrary dimensions ... Of COURSE I used a straight edge to setup the wheels ...

[Phil Thien]

#1 : Coplanarity simply does not exist ... at least, it cannot be maintained. Change a blade .. change tension .. adjust the blade's tracking .. it's GONE !!!

As I've said, coplanar is a poorly chosen word, but it seems to be the word most people reach for when talking about this issue.

#2 : IF you could achieve the elusive coplanarity, tracking the blade would become extremely difficult ... the closer you come to being coplanar, the more it resembles trying to balance an elephant on the edge of a knife blade ... the slightest nudge either way, and the tracking jumps to one side or the other.

It doesn't work like that. We apply tension by increasing the distance between the top and bottom wheels. The band can't "jump" from one side to the next, because the length of the band is shorter than the distance around the wheels. That is why on a properly tuned bandsaw that the band running on the center of the top wheel runs front of center on the bottom. It can't run any further back on the bottom wheel because the band simply isn't long enough.

#3 : If you need to shim the upper wheel whilst attempting the coplanarity exercise, for every tiny fraction of an inch you move the wheel outward, you are substantially increasing the load on the tracking/tensioning components of the saw ... a longer moment of force means you are actually losing leverage the further you place the wheel from it's horizontal pivot point ... and you might possibly be exceeding the manufacturer's recommended loading on those components.

You seem to be arguing from the perspective that manufacturers purposely offset their wheels. They don't. There is no magical proportion to offset wheels. Again, if there were such a value, it would be documented somewhere in service manuals ("How to achieve the proper offset after reinstalling wheels"). The reason you've never read such an article is that bandsaw wheels are already closely aligned, it is designed into the frames and other components.

#4 : Your claim that the manufacturers should/must claim some mystical relationship between the wheels is simply nonsense ... THEY have engineered their products to work a certain way, under specific conditions ... there is simply no need to mess with their engineering.

That isn't what I said, I said they DON'T design them with any sort of wheel offset, otherwise they'd DOCUMENT the wheel offset. Lack of documentation of a wheel offset indicates they likely intend for the wheels to be closely aligned.

#5 : You ARE correct in that at some point I inserted the shim, trying to attain the mythical coplanarity ... when I realized what an utter waste of time that was, I simply removed it .. returning the saw to it's original factory configuration, at which time, it performed flawlessly using Alex's technique.

Likely you created an offset in wheels that were already aligned.

#6 : Any blade, tensioned between two wheels should not have any "twist" in it ... such a condition could only occur when there is an extreme horizontal misalignment of the two axis.

You're going back to my point of my point of diminishing returns. Close enough, is good enough.

But hopefully it is clear to everyone reading this that, as we shift one wheel in relation to another, a little more, and a little more, you get to the point where there is enough offset that the twist induces a vibration.

There are so many of these sorts of posts on woodworking forums it is actually pretty comical.

They go something like this:

(1) I never checked my wheels and my saw is fine, so coplanar doesn't matter.

or (2) I tried adjusting my saw, just made it worse.

Again, people get hung up on this coplanar term and I get that. Wheels don't need to be coplanar.

But as someone that has owned quite a few bandsaws now, I can tell you it has not been uncommon to get a used bandsaw that runs terribly and find that the wheels are way our of whack, either because of something the PO did, or because it was just like that from the factory.

[Bob Wingard]

As I've said, coplanar is a poorly chosen word, but it seems to be the word most people reach for when talking about this issue.



It doesn't work like that. We apply tension by increasing the distance between the top and bottom wheels. The band can't "jump" from one side to the next, because the length of the band is shorter than the distance around the wheels. That is why on a properly tuned bandsaw that the band running on the center of the top wheel runs front of center on the bottom. It can't run any further back on the bottom wheel because the band simply isn't long enough.



You seem to be arguing from the perspective that manufacturers purposely offset their wheels. They don't. There is no magical proportion to offset wheels. Again, if there were such a value, it would be documented somewhere in service manuals ("How to achieve the proper offset after reinstalling wheels"). The reason you've never read such an article is that bandsaw wheels are already closely aligned, it is designed into the frames and other components.



That isn't what I said, I said they DON'T design them with any sort of wheel offset, otherwise they'd DOCUMENT the wheel offset. Lack of documentation of a wheel offset indicates they likely intend for the wheels to be closely aligned.



Likely you created an offset in wheels that were already aligned.



You're going back to my point of my point of diminishing returns. Close enough, is good enough.

But hopefully it is clear to everyone reading this that, as we shift one wheel in relation to another, a little more, and a little more, you get to the point where there is enough offset that the twist induces a vibration.

There are so many of these sorts of posts on woodworking forums it is actually pretty comical.

They go something like this:

(1) I never checked my wheels and my saw is fine, so coplanar doesn't matter.

or (2) I tried adjusting my saw, just made it worse.

Again, people get hung up on this coplanar term and I get that. Wheels don't need to be coplanar.

But as someone that has owned quite a few bandsaws now, I can tell you it has not been uncommon to get a used bandsaw that runs terribly and find that the wheels are way our of whack, either because of something the PO did, or because it was just like that from the factory.

I couldn't disagree with you any more strongly on every point ... bottom line is, I removed the attempted coplanarity effort ... aligned & setup the saw by Alex's technique ... it works perfectly ... that is all I really care about, and I don't really have any interest in arguing the point with you. Done & gone ... PLONK !!!

[Phil Thien]

I couldn't disagree with you any more strongly on every point ... bottom line is, I removed the attempted coplanarity effort ... aligned & setup the saw by Alex's technique ... it works perfectly ... that is all I really care about, and I don't really have any interest in arguing the point with you. Done & gone ... PLONK !!!

LOL, is that the internet equiv. of a mic drop?

For anyone else still reading...

Bandsaws are funny animals, newbies seem to struggle with them more than any other tool in their shop.

I think one large contributing factor is that there are so many blades shipped with bad welds. I'm not going to name names but one brand more than any other has probably caused more users to question the quality/alignment of their bandsaw, than all others combined. Typically they (poster) gets a multi-blade deal and low and behold, all the blades track equally poorly. And it can't be the blades, right? Because they ALL track the same (poor) way. They're wiggling back and forth and cutting crooked and won't ride where they should on the wheels, etc.

So then they visit the forums and ask for advice and they're told maybe their wheels aren't coplanar. Okay now they're adjusting their saw and things are working better with the 1/4" band but horribly with the 1/2" band. Back to the forum, seeking more advice.

Now they're told, "check your tension spring, maybe you have a bent wheel, blah blah blah..."

Maybe they get frustrated and move on and come back to it months later. Maybe they go to a seminar at a woodworking show, maybe they read some books.

But at some point, they buy another brand of blade, and things start to work remarkably better.

But they never realize it was mostly the blade, they blame their earlier technique.

The reality is, I can run my blade like Mr. Snodgrass suggests, or I can run it perfectly centered, doesn't matter. As long as I've got a good blade and my wheels are fairly aligned, I'm going to get pretty darn good results.

I choose to run blades centered because: (1) The manufacturers of every saw (save for the Inca with flat wheels) I've owned have said to do so. (2) Running the gullet on the crown causes excessive tire wear. (3) I get superior cuts and zero drift.

[Erik Loza]

No dog in this fight except to say that on a number of occasions, I have had owners swear to me up one side and down the other that "it can't possibly be the blades" and lo and behold...

I have seen owners get multiple blades of different types with bad welds, even batches from different vendors with bad welds. No vendor seems to be immune to it, either.

Assuming you can get the blade tracking and tensioned properly in the static state, the next "tier" of troubleshooting is, "Try a different blade". Just my 2-cents as aways.

Erik

[jack forsberg]

that Snodgrass is like the "Sham Wow Guy" of 14" band saws hes good

[Chris Parks]

Why would a brand new blade be dull? If I have to worry about that possibility it seems like I can't hope to get anything working.

There has been a run of blade material used in Laguna Carbide blades that was giving the same problem as you describe from new.