Bandsaw blade tracking

[Unisaw A100]

I dunno. I suppose I just like to poke my goad at the Gods.

UA100

[George]

Even a blind hog finds an acorn once in a while?

Seriously, if you can be, consider that the stress on the bearings will be greater if the hubs are not in the same plane. The process by which the blade tracks does, as you have observed, involve compensating for the crown on the tire and the differential friction by tilting the rim. Hub remains in the same place, if you do point geometry.

Imag> >When you do the initial tension-off check. Though that's really to match

[Larry Jaques]

On Mon, 09 Feb 2004 17:28:35 -0600, Unisaw A100 brought forth from the murky depths:

"Coplanarity" is perfection. "Something close" and "whatever tracks" are reality. Any other Qs?

[George]

Not to mention it gives you full tracking authority, as the crown on the tires are aligned.

[Unisaw A100]

Yes. You don't know either?

UA100

[Unisaw A100]

I can and I am.

You'll have to get out the chalk for this one and es'plain it with the wee small werds onna count of the bearings on any given band saw with any given blade will never be in/on the same plane given the changing of the blade or the tension applied to the band.

Sooooooo, you agree that co-planar is a myth?

A non-crowned wheel would be something from a late 70's vintage Delta 14" band saw, right?

UA100

[Larry Jaques]

On Tue, 10 Feb 2004 17:40:38 -0600, Unisaw A100 brought forth from the murky depths:

Um, er, uh, what was the question?

[Larry Jaques]

On Tue, 10 Feb 2004 23:42:13 GMT, Unisaw A100 brought forth from the murky depths:

No, it's a basic config prior to fine tuning for tracking which should lessen bearing wear. If the wheels weren't vertically aligned, both the wheels would have to be canted more to obtain both vertical alignment of the blade and proper tracking on the wheels. That, in turn, would probably tend to stress the bearings a bit more.

You just happen to have one, eh?

[Unisaw A100]

See, this is where I think the train comes off the track. Since neither of us, and no one else I know, is an injineer I'm thinking the force exerted down to the bearings is the same no matter if the wheels are perfectly plumb to the world or slightly tipped.

No, I wouldn't have a banded machine that didn't track. Though during the late 70's there was a Delta (pre-mentioned but snipped) in a shop I worked in. It was at best a brand new boat anchor.

UA100

[Paul Kierstead]

Well, I am not a *mechanical* engineer, but, in the fine tradition of usenet, will offer an opinion anyway.

If the wheels are canted, the pressure on the bearings is going to be uneven; it will be trying to bow its spindle. There will be very little pressure on one side of the bearing and greater then average pressure on the other side. This should cause premature, uneven, wearing.

That being said, bandsaws get abused a lot and the bearings don't seem to wear out very quickly in any case, so it is probably a lot of fuss about nothing. Better to use a tool then worry about wearing it out, or spend hours and hours trying to make it last just a little longer, especially when bearings aren't that expensive anyway.

[Bridger]

it seems to me like the bearing wear/ coplanar issue is one of these things that in theory are real but the closer you get to alignment the smaller the factor, and once you get in the range where the saw will run at all has long since dived in towards zero....

there's no outboard bearing, so that's gonna happen anyhow as soon as you tension the band.

'sides, the spindle cants with the wheel. the force of the band under tension is *almost* straight into the spindle/bearings no matter what.

or hard to get to, or very high speed or for that matter usually run continuously.

[George]

Last chance to out-think the other couples.

The blade, in a perfect world, tracks at the top of the crown. Thus, as the preferred situation, the crowns on the lower and upper should be in line to track the perfect blade. This loads the bearings in their preferred direction.

If the world isn't perfect, you will have to tilt the upper wheel to force the blade toward the crown. If you start at co-planar, you can compensate for the worst blade with the built-in adjustment. If you start out otherwise, you may exceed compensation and still not achieve tracking. Moreover, if you are forced to track too far forward or aft because of non coplanarity(?) you may exceed the adjustment on your thrust or guide bearings.

Oh yes, the load on your bearings will be shifted more from the center of the race, resulting in greater wear....

[Larry Jaques]

On Wed, 11 Feb 2004 04:07:38 -0600, Unisaw A100 brought forth from the murky depths:

The problem is the movement of the force from the flat of the bearing area to the edges of the bearings. Auto engineers moved to tapered roller bearing pairs to overcome the longevity problem and angular loading. (I read all about that in wrenchin' school 30 yarn ago.)

Co-linearity is one of those items the engineers push for. It probably makes a difference only in long-term use in heavy production environments. But why NOT try to set it on your home machine? It can only make the beastie run better. Ditto link-belts. They made a helluva difference on my Griz. My neighbor lost a large branch off one his madrones in the wind a couple weeks ago and I'm going to see if I can get some lengths to resaw. I love the look of that wood.

Pre-Crapsman, eh?

[Unisaw A100]

Don't bet your last dime.

Not only do we have the train off the tracks but it's careening down the embankment, towards the combo orphanage/old folks home/puppy and kitty adoption agency.

A band saw, a "properly" designed band saw, has a wheel. Into this wheel fits a shaft. This shaft and wheel fit into a bearing directly behind the wheel. This wheel, shaft and bearing fit into a cast iron housing where the bearing is seated. At the other end of the cast iron housing the shaft protrudes but before it protrudes we have another bearing also seated into the housing.

What we have here is a cantilever, or, more appropriately for this point and for this argument, a fulcrum and lever (a see-saw Dave). The first bearing, right behind the wheel, is the fulcrum. The wheel shaft acts as the lever.

Still with me? If not then grab your saw manual and take a gander at the es'ploaded parts drawing.

OK, as I've already confessed I'm no injineer but what I do know from experience and that is, any force being applied down onto the top of the wheel by the band is transferred and exerted onto the shaft which in turns puts a great deal (tremendous actually) of downward force onto the first bearing (the fulcrum).

The back bearing, it's got it's hand full with the upward force being exerted by the lever (shaft).

Now, with all of this going on inside your poor band saw, do you really want to peddle the myth of co-planar and bearing wear?

So, co-planar will allow me to buy and use the crappiest blades? Can anyone recommend a good crappy blade?

Ummm, the wheels, they don't give a rat's rosy red rectum about co-planar. They already have their hands full with the job they were designed to do.

Co-Planar Angled Table Saw Fences PVC Causing Dust Collector Fires The Lumber Car

How many more of these myths do we have floating around?

UA100

[Unisaw A100]

George? What have you done with Larry?

UA100

[Jeff Thunder]

10,000 nuns and orphans ...... They were all eaten by rats.

The leg bone's connected to the ankle bone The ankle bone's connected to the foot bone

(Sorry)

I just don't get all the "Oh my god, think of the poor bearing!" wailing and beating of breasts. For a given blade, there's only one "alignment" of the wheels which is correct: the one where the blade tracks properly. My bearings will just have to suffer with whatever that means.

You explode your band saw parts? Hmmm... I'm starting to side more with the bearing.

This comes up every week on the wreck. DAGS, lazy bones.

Aren't those rats supposed to be rancid? Doug, where are you?

I don't know about myths, per se, but the electrical threads often contain some real thigh slappers/side splitters.

How about "real woodworkers never stain cherry"?

[Michael Daly]

You may not be an engineer, but I are.

If the wheels aren't coplanar, the crowns of the wheels don't line up. The blade isn't going to ride on the centre of the crowns by itself. If it's centred on one crown, it's riding the edge of another and it will tend to wander off. Only if the crowns are aligned will the blade run on both crowns with minimal strain.

Once coplanar, you tension the blade and the force on the wheels tends to pull them out of plane. You adjust the top wheel to bring them back more-or-less into line. That's the tracking adjustment.

If you start with non-coplanar, you'll likely have problems with tracking unless you start torquing everything around to make up for it.

Lining it up coplanar is an easier way to start out. YMMV.

Mike

[Larry Jaques]

On Thu, 12 Feb 2004 01:52:55 GMT, Unisaw A100 brought forth from the murky depths:

Hey, hey, hey! We'll 'ave nun o' that here, lads.

Well, whaddya know? My G1012 has a pair of 6202ZZ bearings on each shaft.

OK, so you're a disbeliever. A famous man once said

What me worry?

[Unisaw A100]

Michael Daly

Finally, someone who admits to being one.

OK, we know this to be true.

OK, we know this to be true.

In theory this is true but as I have said, my wheels aren't co-planar and the band(s) ride(s) as true as anything I've seen.

OK, "maybe" someone could check it with some snot, boogers and a stick (or a TS Aligner Jr.) and find it out by half a thou but so far this gross alignment isn't an issue.

OK, I think I've found the crux of the biscuit. Define what you mean by minimal? Are you saying there's always strain no matter the alignment? Even in a perfect world? Sorry, I know the answer to this. I'm baiting you. OK, there, I admit it.

OK, we know this to be true. And we should add, that the given make-up of every blade is different and therefore each and every blade will have a different effect on the wheels?

OK, we know this to be true.

But, but...

But, but, my wheels aren't co-planar and my band(s) ride(s) right down true and center on the wheels. I'd be happy to open up my shop to any wreckreite who would like to ponder this problem (or stand in awe as they gaze upon it) with me or who doesn't believe me or who would like to further their studies on the subject. But in the mean time, I still say you're all blowing smoke up a rat's rosy red (and rancid) rectum to say it's worth any more time than to note it, i.e., don't get your undies inna bunch over it.

UA100

[Unisaw A100]

Yes I believe you are correct but I think it was Charlie Self who first spoke the line.

UA100