How much should your bandsaw thrust bearing spin?

[Edwin Santos]

The title of the post pretty well sums up the question. I raise it because I've noticed some posts in the archives from people who suggest the thrust bearing spinning at all means either the blade is dull or there is not enough tension being applied. One post made a case that the thrust bearing should not even be necessary other than a warning gauge that you're not using enough tension.

Logic would say feed rate and blade choice (width, tpi, gullet size, set) must also play into this balance. How far you set the thrust bearing back from the blade surely is a factor also. I tend to set mine close, maybe 1/32" back, just outside of touching the blade when turning the wheel by hand.

What about others? Are you in the spin or no spin camp? Lazy or banshee spin? Maybe some don't pay attention to the thrust bearing spin rate much at all?

Thanks for commenting!
Edwin

[Rod Sheridan]

It depends.

If I'm looking for excellent cut quality I use a low feed rate that's a mix of finish and chip load considerations, with less use of the thrust bearing.

If I'm ripping rough material to break it down, I'll use a high feed rate which has high chip load, poor finish and the blade against the thrust bearing.

If I have a log that's too big on the band mill, I'll reduce the feed rate enough so that I can completely remove the guide assembly..........Regards, Rod.

[David Kumm]

When I'm running a 1" carbide blade, I seldom run the back bearing for more than short periods. I've had better luck with higher tension and less bearing engagement with those expensive blades. When running a 1/4" bimetal, I tension up to 30,000 and the bearing will still run more than with my resaw blades. Because the blades are small, inexpensive, and bimetal, I don't care so much. With a $250 blade, I try to eliminate any heat from a bearing rubbing the band. It takes 25000-30000 on my meter to avoid that. Not all saws can tension to that level. Slowing the feed rate or running a thinner band are alternatives. Dave

[John K Jordan]

. . . Are you in the spin or no spin camp?

I'm in the follow my mfgrs instructions camp. In my manual:

. . . turn the bandsaw on and inspect that the upper,
lower and thrust bearings are not turning. All bearings
should not turn unless pressure from workpiece is applied
to the blade. If bearings are turning under no pressure,
repeat steps to adjust the blade guides.

This is how I've always done it and it's worked for me what I use my bandsaw for.

JKJ

[Al Launier]

I set up my BS the same. Works for me - no problems yet.

I'm in the follow my mfgrs instructions camp. In my manual:

. . . turn the bandsaw on and inspect that the upper,
lower and thrust bearings are not turning. All bearings
should not turn unless pressure from workpiece is applied
to the blade. If bearings are turning under no pressure,
repeat steps to adjust the blade guides.

This is how I've always done it and it's worked for me what I use my bandsaw for.

JKJ

[Edwin Santos]

I'm in the follow my mfgrs instructions camp. In my manual:

. . . turn the bandsaw on and inspect that the upper,
lower and thrust bearings are not turning. All bearings
should not turn unless pressure from workpiece is applied
to the blade. If bearings are turning under no pressure,
repeat steps to adjust the blade guides.

This is how I've always done it and it's worked for me what I use my bandsaw for.

JKJ

The question I'm raising is not addressed in your manual excerpt.
I'm asking about the interaction of the thrust bearing and the blade when under load. Your quote refers to examining the guide and thrust bearings under no pressure.

[Brian Nguyen]

Mine is set at 1/32, and barely spin if I'm feeding slow, but if I'm forcing a cut (roughing it through) then it's a constant whirl. If I'm resawing, then I get a visit from the banshee.

[Lee Schierer]

I'm in the follow my mfgrs instructions camp. In my manual:

. . . turn the bandsaw on and inspect that the upper,
lower and thrust bearings are not turning. All bearings
should not turn unless pressure from workpiece is applied
to the blade. If bearings are turning under no pressure,
repeat steps to adjust the blade guides.

This is how I've always done it and it's worked for me what I use my bandsaw for.

JKJ

Exactly what I do.

[lowell holmes]

Exactly what I do.

How do you contribute?

[Lee Schierer]

How do you contribute?

Simply click on the word Contribute at the end of my signature or click on the word Donate at the top of every page. Follow the directions at the page that opens.

[Lee Schierer]

The question I'm raising is not addressed in your manual excerpt.
I'm asking about the interaction of the thrust bearing and the blade when under load. Your quote refers to examining the guide and thrust bearings under no pressure.

As was stated: "All bearings should not turn unless pressure from workpiece is applied to the blade."

[Van Huskey]

The correct answer is it depends.

While not answering the question posed most would agree bearings should not spin under no load of the band. That, however, is also due a caveat, if one has replaced their metal bearings with ceramic discs (Space Age Ceramic for example) then it isn't an issue to run the "bearings" JUST touching the band under no load and thus they will gently rotate while the saw "idles".

I attempt to do everything I can to prevent the blade touching the bearings. I use the widest blade I can for an operation and use as much tension as the blade will tolerate in order to have the highest beam strength. The blade width, strain, stock thickness, stock density, blade sharpness, tooth aggressiveness, how tight you set the guides and feed rate all come into play. It is all a matter of give and take and I doubt anyone avoids touching the guides all the time and likewise, I doubt anyone touches the guides all the time save for ceramic or "soft" block guides that are purposely set touching the blade.

In general beam strength is your friend within the limits of the saw and blade.

[John K Jordan]

The question I'm raising is not addressed in your manual excerpt.
I'm asking about the interaction of the thrust bearing and the blade when under load. Your quote refers to examining the guide and thrust bearings under no pressure.

You asked five questions. The one I chose to try to answer was "Are you in the spin or no spin camp?"

Perhaps I did not answer clearly. I pitch my tent in the no spin campground as implied by the excerpt from manufacturer's instructions "All bearings should not turn unless pressure from workpiece is applied to the blade." This is unambiguous. I have several bandsaws for cutting wood and all but the WoodMizer band sawmill have the same instructions: adjust the guides so the bearings do not spin when the saw is idling. This is regardless of the rotational orientation of the thrust bearings. (The Woodmizer guide/thrust bearings are of a design I suspect is not useful to a shop bandsaw.)

I adjust for a very small gap behind the blade, the smallest gap I can make without the thrust bearing spinning. I have never measured the gap. There is no spin on the thrust bearing until cutting pressure pushes the blade into the bearing and to cause it to spin. This has something to do with the tension as with the deflection due to the pressure of the wood against the teeth working against the beam strength of the blade, related to the thickness and width of the blade as well as the distance between the top and bottom wheels and probably the type of steel. I have never tried to measure the pressure of the wood against the teeth but it would be easy enough to do. The pressure will get higher the faster you cut, the tougher the wood, the thicker the wood, the more friction against the sides of the kerf due to buildup on the sides of the blade, and the dullness of the teeth. When the dullness begins to annoy me I stop and sharpen the blade. If the thrust bearing is adjusted for "no spin" and it suddenly starts spinning it indicates the blade moving backwards on the crown of the wheel.

I tension my bandsaw blades with the assistance of a Starrett bandsaw tension gauge since I have one and I don't trust the flutter, tone, finger deflection, and other methods including the I have no idea but it seems to work ok method. I adjust the bandsaw wheel alignment so the blade rides on the top center of the crown on the tires. That's all I know about that.

There are a few books I used to learn about bandsaws, one by Lonnie Bird and a couple by Mark Duginske. Either of these books might answer your questions. While I don't agree with everything either author says they both agree on one thing: set the thrust bearings so they do not spin until the stock is fed into the blade. Duginske goes further, saying "if the thrust bearings are always in contact both will wear prematurely." I'll go one step further and say that if the blade is very lightly touching the type of bearing designed so the rotational axis is towards the operator instead of sideways, if the back of the blade is very lightly touching the bearing can have a groove worn into it rather quickly if it gets "gummed" up so it no longer rotates freely.

Duginske points out another thing about thrust bearings that many people apparently don't know or ignore: the upper bearing must be aligned carefully with the lower bearing. If not and the back of the blade contacts one before the other the blade can then "twist or deflect sideways" and can cause problems with the cut.

JKJ