Bandsaw Thrust Bearing Alignment

[Dennis McDonaugh]

The manual for my MM16 says the back of the blade shouldn't contact the bearing, but I find this hard to achieve even with a new blade, lots of tension and a slow feed rate. The saw cuts great, but the clearance goes from 1/4" to nothing in just a few feet of cutting. The blade doesn't move if I just let the saw run without cutting anything. Is there anyway to stop this from happening or should I even be worried about it?

[ken masoumi]

I don't know about your MM16 but in general when setting up a 14" bandsaw:
Let the bearing touch the back of the blade then move it back 1/32" or less.
After tensioning the blade is done the thrust bearing should be set close enough so it's almost touching the back of the blade minus 1/32" which means it only contact the blade when you start to cut.

[ken masoumi]

I remember a Jim Becker had a review of this Bandsaw with a few pictures but can't find it.

[Jery Madigan]

Sounds like you need more tension.

[Dennis McDonaugh]

I don't know about your MM16 but in general when setting up a 14" bandsaw:
Let the bearing touch the back of the blade then move it back 1/32" or less.
After tensioning the blade is done the thrust bearing should be set close enough so it's almost touching the back of the blade minus 1/32" which means it only contact the blade when you start to cut.

The manual says 1/4" clearance for blades less than 1" and 5/16" for 1" and larger and that the bearing should not touch the blade when in operation.

[Dennis McDonaugh]

Sounds like you need more tension.

That's what I thought, but I've got it tensioned to 20K per my Iturra tension meter. The blade is pretty tight.

[Erik Loza]

Dennis, what width blade is this?

Erik Loza
Minimax USA

[Dennis McDonaugh]

Dennis, what width blade is this?

Erik Loza
Minimax USA 1/2" Erik.

[ken masoumi]

but the clearance goes from 1/4" to nothing in just a few feet of cutting. ?
Dennis,does the manual say that the 1/4" clearance will be maintained during the cut?it just wouldn't be possible with all the heat that's generated during a cut to keep that 1/4"gap,what you described (the clearance goes from 1/4" to nothing) sound more likely to happen.

[Erik Loza]

1/2" Erik.

Straight cut or curved cut? And what size/species of wood?

Erik Loza
Minimax USA

[Dennis McDonaugh]

Straight cut or curved cut? And what size/species of wood?

Erik Loza
Minimax USA

Straight cut, alder about 8" tall. The cut is good, smooth, consistent width and the blade cuts cleanly.

[Dennis McDonaugh]

Dennis,does the manual say that the 1/4" clearance will be maintained during the cut?it just wouldn't be possible with all the heat that's generated during a cut to keep that 1/4"gap,what you described (the clearance goes from 1/4" to nothing) sound more likely to happen.

Doesn't mention anything about keeping the gap you start with, just that the blade should not contact the bearing

[glenn bradley]

Doesn't mention anything about keeping the gap you start with, just that the blade should not contact the bearing

It will be interesting to see how MM addresses this. I used to set the gap with a piece of paper but now just do it by eye leaving just enough room to let light through. the bearing is not touched when the saw is running but, immediately comes in caontact when a cut starts. If the blade NEVER touches the thrust bearing, why have one ;-)

[Dennis McDonaugh]

It will be interesting to see how MM addresses this. I used to set the gap with a piece of paper but now just do it by eye leaving just enough room to let light through. the bearing is not touched when the saw is running but, immediately comes in caontact when a cut starts. If the blade NEVER touches the thrust bearing, why have one ;-)

That's what I was wondering--if it was a problem or not. I normally just resaw with it and have had a 1" blade on it for years and don't think touching the bearing was an issue with the thicker blade.

I set the gap for the two side guide bearings with a dollar bill, but not the thrust bearing.

[Phil Thien]

On every bandsaw I've used (and that INCLUDES flat-tire/wheel saws), you set the thrust bearing just behind the blade. When you aren't cutting anything, the wheels/blade spin without hitting the bearing.

But once you start cutting, the force pushes that blade into the thrust bearing. The purpose of the thrust bearing is to keep the blade running on the wheels near where you'd like.

Without the thrust bearing, the blade will creep-back, either increasing or decreasing tension (depending on the camper or crown of the wheels), and eventually either the blade will break or it will ride right off the back of the wheel.

No real harm in having the blade hitting the thrust bearing, either. At least I've never experienced any.

[Erik Loza]

On straight cuts, regardless of blade width, I set the thrust bearing so that the blade rarely if ever comes into contact with it during the cut. The wider the blade is, the greater that gap would be. Italian bandsaws have flat tires and enough beam strength that you should be able to let tension and tracking do the work for you rather than the guides. The guides, in this case, are there simply to provide protection from over-travel in case the blade jerks or makes some other unexpected movement. Again, this is talking about straight cuts, not curved cuts.

All that being said, 1/2" blades on an MM16 can be fussy to rip with. This is due to the amount of free blade between the flywheels. It's a phenomenon of all tall-resaw machines. That's a lot of blade hanging out there in space and finding the sweet spot of tension that this or that blade wants in order to cut straight can be time consuming. Personally, I prefer 3.4" or 1.0" blades for straightline cutting on the MM's. Less fussy about tensioning. At least for me.

Best,

Erik Loza
Minimax USA

[Phil Thien]

Erik, what is the downside to relying on the thrust bearing to prevent blade travel?

[Erik Loza]

Erik, what is the downside to relying on the thrust bearing to prevent blade travel?

Too much feed pressure and you can dull the blade as well as well as possibly induce wander into the cut line.

Erik Loza
Minimax USA

[Dennis McDonaugh]

On straight cuts, regardless of blade width, I set the thrust bearing so that the blade rarely if ever comes into contact with it during the cut. The wider the blade is, the greater that gap would be. Italian bandsaws have flat tires and enough beam strength that you should be able to let tension and tracking do the work for you rather than the guides. The guides, in this case, are there simply to provide protection from over-travel in case the blade jerks or makes some other unexpected movement. Again, this is talking about straight cuts, not curved cuts.

All that being said, 1/2" blades on an MM16 can be fussy to rip with. This is due to the amount of free blade between the flywheels. It's a phenomenon of all tall-resaw machines. That's a lot of blade hanging out there in space and finding the sweet spot of tension that this or that blade wants in order to cut straight can be time consuming. Personally, I prefer 3.4" or 1.0" blades for straightline cutting on the MM's. Less fussy about tensioning. At least for me.

Best,

Erik Loza
Minimax USA

Normally I use a 1" blade, but I had a couple woodslicer blades from Highland Hardware and wanted to use them and they are only half inch. One is only 143" long (that was the size they sold for the MM16 many years ago) it's really not a good fit.

Now I understand the different clearances for a 1" and 1/2" blade.

That brings up another issue I wonder about. The MM16 says it takes blades from 143-145 inches long. Won't that affect the reading on the on-board tension gauge? I had not done a lot of bandsawing to begin with and my tools were in storage for over two years between 2011-2013. I made two pencil marks on the tension gauge in pencil and can't remember why. They're pretty far apart and I believe they were for two different length blades.

[David Kumm]

I almost never rely on the back bearing for any blade. I tension until it doesn't move during the cut. A 1/4" blade will move somewhat even at 30000 lbs but larger blades won't. Downside of spinning the bearing fast is that it adds heat to the blade. I broke Lennox carbide blades until I tensioned them enough to stop spinning the bearing. Not a scientific sampling but worked for me. The length of the blade dos not affect the tension gauge on the saw. They are not very reliable and not always repeatable but you get a feel for how the blade operates after time. There are lots of opinions but I'm a fan of high tension so my guides are kind of irrelevant. Dave

[Erik Loza]

Dennis, that is possible. Blades stretch and also, if you sampled, say, half a dozen blades of a certain length from this or that mfr., you would probably find them not all the same length.

I can tell you how to calibrate that on-machine tension guage if you're interested.

Erik Loza
Minimax USA

[Dennis McDonaugh]

Dennis, that is possible. Blades stretch and also, if you sampled, say, half a dozen blades of a certain length from this or that mfr., you would probably find them not all the same length.

I can tell you how to calibrate that on-machine tension guage if you're interested.

Erik Loza
Minimax USA

I am interested to know how to do that Erik.

[Phil Thien]

I almost never rely on the back bearing for any blade. I tension until it doesn't move during the cut. A 1/4" blade will move somewhat even at 30000 lbs but larger blades won't. Downside of spinning the bearing fast is that it adds heat to the blade. I broke Lennox carbide blades until I tensioned them enough to stop spinning the bearing. Not a scientific sampling but worked for me. The length of the blade dos not affect the tension gauge on the saw. They are not very reliable and not always repeatable but you get a feel for how the blade operates after time. There are lots of opinions but I'm a fan of high tension so my guides are kind of irrelevant. Dave

How fast can you feed (let's say) 6" wide (or tall, I suppose) walnut when you are relying on the tension and not the bearing? Like let's say a 6' long, 6" high board, how fast can you run that through your saw w/ just tension keeping the blade in place?

And do your blades actually get hot while cutting? I've only actually gotten blades hot when cutting ferrous, never with wood. On my friend's Laguna (which I think is an ACM from Italy), even when I've been feeding thick stock very quickly for a while, when I stop the blade and feel it, it is not really hot at all.

[David Kumm]

Phil, On my old Olivers I can't run 6" through fast enough by hand to test it. I have a feeder to put on the 36" but it still is sitting in the " too hard " pile for now. The Olivers both run at about 6700 fpm so the blade heats up the bearing which in turn heats the blade and over time seems to fatigue the 1" Trimasters I run. When you get over 10" feed rate becomes important to match but under that it almost takes a feeder to overwhelm the saw. Dave

[Phil Thien]

Phil, On my old Olivers I can't run 6" through fast enough by hand to test it. I have a feeder to put on the 36" but it still is sitting in the " too hard " pile for now. The Olivers both run at about 6700 fpm so the blade heats up the bearing which in turn heats the blade and over time seems to fatigue the 1" Trimasters I run. When you get over 10" feed rate becomes important to match but under that it almost takes a feeder to overwhelm the saw. Dave

Well one of these days I'm going to have to find some time to play with some large bandsaws a bit. I think all the rules must change from the small saws I am accustomed to in my shop. Maybe because the small saws can't achieve the tension of the larger saws? Maybe I never increased the tension high enough the few times I tensioned huge saws?

For example, my saws only run at 3000-fpm, but I've run them for half an hour or longer riding the trust bearing (I buy most of my walnut as 8/4). Now, in my case my thrust bearing is probably half the diameter of yours, I expect both our thrust bearings turn at approx. 18k-RPM when the blade is riding them, and I've never thought my thrust bearing was particularly hot. So maybe the larger diameter thrust bearings can't handle 18k? It is kind of interesting.

I'm just a bit surprised because a lot of what I've read in these threads of late has directly contradicted what I've read in the various bandsaw books, and also my own personal experiences. But like I said, my experiences on real big bandsaws is limited to a friend's ACM-made Laguna and the big Crescent (I think) we had in high school.

But in the case of the Laguna, for example, they have ceramic thrust bearings that are brought right up to the blade, Laguna tells you to do that. You'd think that would be a great recipe for a hot blade, hotter than riding on a spinning bearing. But the blades don't seem to get hot.

LOL, I'm confused.

[Erik Loza]

I am interested to know how to do that Erik.

1.) Fit, track, and tension the blade you use most frequently onto the machine.
2.) Unbolt the the black plastic tension gauge housing from the frame and turn it around in your hand.
3.) Loosen the pointer with a screwdriver and adjust to correspond on the yellow decal to the width blade you have on the saw.
4.) Tighten pointer clamp and re-install black plastic housing onto the machine.

Procedure will be the same on any Italian saw (ACM/Agazzani/Centauro). The tension gauge can only be "ballpark-accurate", since you can only calibrate it for one particular blade (which is why I suggest doing it with the blade you use the most...) but this will give you an consistent and repeatable reference point to work from.


...Maybe because the small saws can't achieve the tension of the larger saws?...

Yep ^^^^

In my experience, the biggest hurdle new Italian BS owners seem to struggle with is trying to "out-think" the machine. This is normal because the smaller saws we are all used to (or even bigger ones, if they are solid cast iron...) don't have frames that can really get big blades into the tension range they want in order to cut straight. On a smaller saws, you are fussing with the guides all the time, trying to compensate for what the chassis cannot do. You don't have to worry about any of this with an Italian machine. The advice I give all new MM bandsaw owners is, "Cut first, THEN adjust as needed." You will create more problems for yourself, for example, by setting the guides too close to the blades than you will by having too much free space.

Again, this sounds counter-intuitive if you are used to a small, domestic-style BS but it's the correct way to set up any Italian machine. Hope this makese sense,

Erik Loza
Minimax USA

[Phil Thien]

Again, this sounds counter-intuitive if you are used to a small, domestic-style BS but it's the correct way to set up any Italian machine. Hope this makese sense,

Erik Loza
Minimax USA

Well I'm going to give it a shot on the ACM-based Laguna next time I'm there, but my recollection is that the guides can't be backed off very far (at least the rear guide). But I'll try. The Laguna guides are designed to hug the blade.

I found a manual for a Centaruo bandsaw online yesterday and that said to adjust the thrust bearing so it is 3 [sign for division] 4 mm behind the blade. I had to laugh at that because as I search for clarity, I find less and less. If they mean 3/4mm, that would be about .003". But it seems unlikely they'd use that notation. I think they meant to say "3-4 mm" that would be about a tenth of an inch.

And now I have to convince my friend to order some new blades for testing, which shouldn't be too difficult as he is more of a tool collector than a tool user. And then he has to stand there and watch while I tension the snot out of them and back-off all the guides.

This should be good.

[Dennis McDonaugh]

Thanks Erik

[David Kumm]

I did run the ceramic guides when I used the ACM LT18. Even with an upgraded spring it relied on the guides. Smaller blades will as they don't have the beam strength even at high tension. I think the ceramic did keep the blade cooler but the Laguna ran at 4000 rpm so not comparable to the Olivers. Dave