Converting a Bandmill to Narrower Blades

      A sawmiller trying to put a previously owned Mighty Mite bandmill back into service gets advice on dealing with blade tracking issues. January 19, 2012

Question
Has anybody had experience converting an old Mighty Mite bandmill to run on narrower blades? Mine was built in the early 80's, uses 2" blades and has some pretty archaic guides. The tracking is really sensitive and wants to leave the blade riding more to the outside of the wheel, more so on the drive side. This results in a good portion of the blade running on the outside of the guides even with them moved as far forward as they will go. It looks like even if I could get the blade to go back farther in on the guides with the tracking, the guides would be better suited for a 1 3/4 width blade. If I try to track the blade back onto the guides, the blade wants to jump off the back of the idle wheel before the blade gets to the stop collar on the guide wheel. Any ideas?

Forum Responses
(Sawing and Drying Forum)
From contributor R:
Maybe the wheels need re-crown?



From contributor O:
Not sure what type of wheel you have, but they might be out of alignment to the main sawhead frame. If the wheels are held on to the shafts by bushings, you may be able to just shift the idle side back or forward, whichever is necessary. And yes, there has to be a crown on the wheels for the blade to track. You do not want the teeth to be on the wheels at all, if so the wheels will take the set out of the teeth on one side, the blade will not cut.

Not sure if you can get a 1 3/4" blade, but you can get 1 1/2" bands, which might be more suited. But if your 2" band is tracking on one wheel on one edge, and the other wheel on the opposite edge, if there is not a crown problem, there may be a wheel alignment issue. Did you just recently get this mill?



From the original questioner:
Thanks. I did just recently get this mill. In a testimonial to Mighty Mite, this mill had been sitting unused near the ocean here in Hawaii for nearly 25 years. The original motor had been removed and was inside but dismantled into several dusty boxes. After reassembling it and replacing only the magneto, plugs and wires, carb and fuel pump, the motor fired right up. The mill only needed a few new switches in the control box. A couple of hydraulic hoses and new drive chains and a blade, and it was sawing once again. I am just trying to fine tune this thing right now.

I have looked at the bearings on both the idle wheel and the drive side and it looks as if they are a little loose. When the blade is tensioned, both wheels tilt in a very slight bit. I can compensate with tracking, but when I do, the blade will run with the teeth plus about 1/8th-3/16th of the blade showing on the idle side and about 1/2 inch plus the teeth showing on the drive side. It will hold this tracking but results in close to half of the 2 inch blade running forward of the guides, with them adjusted as far forward as they will go. I think there may be a way to move the drive and idle wheels back and forth and I may have to change the bearings to get true wheel alignment, but I ultimately would like to get away from the 2 inch blades. There are not many options for these so they tend to be expensive to get here with shipping $50+ per band. The first set I bought were sterling blades. They last 2 hours with hardwoods and then they are dull. They last 5 hours with softwoods, but then they break.

I am leaning towards converting this mill to run a thinner more readily available blade to try and cut down on blade cost. My thinking is that a thicker band removes more material but could be more stable, but a thinner one removes less, so the saw might not work as hard and therefore maybe more stable as well. Might be a 6 of one/half dozen of another sort of thing? I have fabricating skills and tools so I know I can build a better guide wheel system for this mill. So I am just trying to find out if there are any advantages or disadvantages to this type of conversion besides wanting cheaper blades.



From contributor R:
Maybe ask Mighty Mite for some advice?


From contributor S:
I had a MM mill. It was very stout. My guess is you have the wrong blade (saw). The largest saw that fit my MM was a 1 1/2 X .45". If you have 19" diameter wheels then I am sure you have the wrong saw. The tracking on my mill was bulletproof.


From contributor B:
I have a Mighty Mite bandmill (1980's vintage) and I understand fully the blade/guide issue you describe. I had thought of going to a 1-1/4 blade (Wood-Mizer standard), but it would have been about $1400 to convert and I didn't figure it worth it when I figured how many $35 blades I could buy (Suffolk Machinery's Timberwolf blade works great). I am more of a hobbyist, but my biggest problem with the mill is the hydraulic feed. The hydraulic valve must be ported more for the faster feed rates of softwoods and I saw mainly hardwoods (white oak, walnut, cherry, locust).


From contributor S:
I had a Mark IV machine, so perhaps this is not the same for you, but the feed speed control valve in the Mark IV needs to be moved in order for the feed to work correctly. You would want to make sure that the control valve is after the motor.


From the original questioner:
Thanks for the post. I looked at the mill today and I do have 19" wheels. The guides, however, are 1-1/2" wide so a 1-1/2" blade will not work, as the teeth would pass through the guides and take the set out. It looks like a 1-3/4" blade would work well. I did find out that I should be able to move the wheels back on the shafts to get more of the blade back into the guides. This should take care of the issue I have with too much of the blade floating in front of the guides even with a 2" blade. After learning more about the tracking system, it seems to be behaving the way it should, and the biggest problem is more than likely the bearings on the main shafts.

As for the feed speed that has been brought up with this particular mill... My biggest problem has been not being able to go slow enough, not fast enough. If I have the speed set too high, I get a bad cut with the hardwoods. In order to get a good cut I have to slow the mill speed down to the point that it just sort of jerks along, and needs a constant adjustment to keep it moving. But then again this problem may have everything to do with half of the blade floating in front of the guides.



From contributor S:
The standard guides are 1 1/2" wide and will work with 1 1/4 saws. The guides can be adjusted so the rollers are not on the saw teeth.

As to speed, once I modified the hydraulic plumbing so that the flow control valve was after the pump, I could obtain any speed. This repair required the addition of a flow control valve on the pump.

As to wavy cuts, the saws needs to be sharp. I had less trouble cutting hardwood than Douglas fir. Going too slow can be an issue too. It sounds like your saws are dull (they should be so sharp that if you don't wear gloves to handle the saw it will easily cut you).
Forget the 2" saw. I gravitated to 1 1/2 saws but they need to be .045 or thinner; such as the Timber Wolf saws. I believe you will find that most folks are using 1 1/4 and 1 3/8 saws.



From the original questioner:
That makes sense about the guides. The top guide has a stop collar built into it and I just assumed that the blade would have to be riding all the way back on the roller. I do know that the more blade that is in the guide, the better, as with all bandsaws.

I do not think that the problem is dull blades unless these ones that I am using are extremely low quality. They are sterling blades out of a supplier in Canada. When I purchased them I went by the spec that was in the book. I have this problem even with new sharp blades (I believe they are sharp - one of them gave me seven stitches one night just brushing against the blade while covering the machine for the night). I ordered a set of blades from Wood-Mizer so I can compare the quality. They are the thinner blades (.042) but I think I ordered the 2" ones. I think that in order to run narrower blades I will have to move the drive and idle wheel back in order to get more adjustment out of the guides. Actually I will have to do that anyways in order to get more of the two inch blades back into the guides.

As for the speed control, the valve for the speed is after the pump on this one, it is on a manifold with all the other controls.



From contributor S:
You can check the speed control by measuring the speed at the beginning and again at 10' and 20'. My guess is it will vary by about a factor of two. That is what mine did, but perhaps I have a newer manifold.


From the original questioner:
The speed seems fairly constant once the carriage is moving. The longest logs I have milled though are only 10 feet long.


From contributor P:
I bought a Mighty Mite Mark III several years ago, used, pre-owned several times over. I had trouble getting a cut - broken blades, wavy cuts, etc. Found the bearings on the drive wheel bad and shaft galled. Previous owner had changed bearings on the idler wheel, but cracked the wheel. I bought new wheels, drive bearings, shaft, and guides from Mighty Mite to convert to 1 1/4 in blades on recommendation from Mighty Mite. Narrower blades have less drag than the 2" that came standard.

If there is any slop at all in the bearings, they need to be replaced. I just replaced the idler bearings because the cuts started getting wavy, and I couldn't correct with sharp blades, different tooth sets, or changes in feed rate. Mighty Mite is pretty proud of their bearings, but have a quick response time on the parts.

There is a feed speed adjustment on the hydraulic valve. You should adjust the feed to dead slow to enter a cut, then increase feed according to the wood being cut.



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