Troubleshooting Band Breakage

A bandmill operator tries to figure out why his bands have started breaking after one or two resharpenings. September 17, 2008

Question
My bands have been breaking after one or two sharpenings. I have been sharpening my blades for several years. I notice my bandwheel has a slight wobble in it. All of the bolts are tight and the wheel itself is tight. I have a Timberharverster and was wondering how to realign the wheel? Also could this be the problem for the blades breaking?

Forum Responses
(Sawing and Drying Forum)
From contributor A:
Belted band wheels are not good. Replace them with Cooks all metal wheels. I have two mills each with the different wheels on them. My second one is about to get the all metal wheels. Go to a big mill and you will find out that the wider mills use all metal wheels. The reason is plain and simple, less vibration on the band.


From contributor B:
You don't need to spend hundreds of dollars on new band wheels. There are tens of thousands of saws out there running on belted wheels that are doing just fine.

If the wheel has a wobble but is still tight, you've somehow bent the wheel which is a major feat and rather unlikely. If you can grab the wheel and wiggle it, the bearings are going. I'm guessing it's the idler wheel you're talking about as that bearing is a common wear item on a TH. The wheel will have to be taken off the idler hub, the bearing removed, and a new one pressed in.

Your blade breakage problem is caused by something other than a wobble in the wheel. Have you always experienced such short blade life? The cause can be anything from improper sharpening to guide wheel issues to waiting too long to change out dull blades and pushing them to the point of heating up. It may also be caused by using a blade too thick for the diameter wheels you have and you are experiencing premature metal fatigue.

More input is needed. The only time you need to re-align the wheels is if you are experiencing a tracking problem.


From the original questioner:
I have been sharpening my blades for over eight years now and don't think that is a problem. The roller guides look good as well. I called Woodmizer to discuss the problem with them. I thought the problem might be in the blades. They told me to send them one of the blades and they would examine it. I haven't sent them anything yet because I have always had good luck with their blades. I just replaced one of the bearings recently and have discovered this problem. I don't think I need all metal wheels either. I have been sawing for a long time with belted wheels and have not had this problem until now. The blades are the same size as normally use.

From contributor R:
We swapped out our band wheels with all metal wheels from cooks. We have been running our timber harvester for about five years. We installed cooks all metal wheels about four years ago and have never been sorry. We also had lots of blade breakage problems with the old wheels. We rarely break any blades now, mostly we use them till they are too narrow.

If you do want to realign your wheels you just need to loosen the four bolts that hold the brackets on both sides of the head that the band wheel bearings and shafts are mounted to. You almost have to have somebody help you - one person to hold the band wheel in position while the other person tightens the bolts back down.

Also make sure your wheels are co-planer. Your blades can track fine and the band wheels will still be out of co-planer. This will definitely break your blades. Also you might want to check your blade tension. Be sure and measure the spring. Our gauge was off right from the factory.


From contributor S:
To the original questioner: Can you describe the "wobble" a little more? When you are running the saw does the blade wobble side to side or up and down?

From contributor G:
I too have been using belted wheels for 23 years without a problem. You said the wobble showed up after you changed a bearing. Could that be the source of your trouble?

From the original questioner:
The wobble is side to side. I don't think I need to change the bandwheels because I had long blade life in the past.

From contributor S:
It sounds like one of the wheels isn't on straight. The other possibility is some bump or unevenness on the bandwheel faces.

From contributor W:
Make sure you replaced the old bearing with the correct one. Your old one will probably be a preloaded, angular contact, double row ball bearing with the proper class. All the markings should be on the side of race on old bearing.

From contributor E:
You can verify how "true" the wheel(s) are by using a magnetic base and dial indicator. The base can be attached to the saw frame and you can rotate the wheel and see how the indicator value changes. You can then remove a wheel that is not turning true and do the same measurement on the axle to make sure the error is not in the axle/bearings.

You could try cleaning the mating surfaces of the wheel/hub and mount the wheel again. I broke down and purchase a magnetic base and dial indicator to measure my wheels. The machine builder (Mighty Mite) does not verify each machine they build. They pay a third party to machine them true, but I always like to verify things are right myself (I wish they felt that way). My wheels are true within my ability to measure.

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