Troubleshooting Blade Diving on a Bandmill

A beginner gets help with a wandering blade problem on a borrowed bandsaw mill. October 19, 2013

Question(WOODWEB Member):
I'm just getting started sawing with a wood mizer LT40 on loan from a neighbor. Are there any tips and/or resources to help me get started? What strategies are there for getting the most out of the log (i.e. different ways of dividing up the cant, flitch cutting or anything else)?

I'm having a small problem with starting the cut. I line up the cut where I want it, but as the blade enters the wood it tends to drift upwards (maybe up to a 1/2") in the first 6" or so of the cut. This happens pretty consistently, even with a new blade entering the wood very slowly. I'm sawing mostly poplar and oak.

Forum Responses
(Sawing and Drying Forum)
From contributor A:
The "diving" is usually a sign of dull blade. If, as you said, a new blade was used also,the first check is tension on blade, then check tolerances of band guides. I don't own a woodmizer but most react nearly the same. Speed can cause diving and wandering also.

From contributor B:
Check for proper deflection while checking guide bearings.

From Contributor C:
On a borrowed mill I'm not sure I would start learning how to adjust the machine as getting these things square and true involves a bunch of things, but maybe he has the blade pitch guide. It's a little aluminum bar that clips on the blade and tells if the guides are holding the blade square, or parallel to the bed for straight cuts. If the mill cuts true for the owner you may be starting the cut too fast, but also trees with large butt flared tend to force the blade to follow the grain as you are cutting across a lot of grain in the flare. Otherwise, alignment, sharp blades and slow entry of logs. Old dried out logs will have very hard ends as well. Wrong pitch and set of blade causes trouble, though a new standard 10 degree blade should cut oak and poplar fine.

From contributor D:
New blade, proper blade tension, and blade alignment are steps in the right direction. If all that appears up to snuff, then check the main drive belt tension and condition. The power to the blade comes from the blade velocity or speed. If the main drive belt slips, the blade speed drops and then the blade tends to wander. Main belt slippage is deceiving as the engine will sound fine as itís under less load. The engine should sound like itís under load when the blade enters the wood.

Another thing to check is the top engine RPM. Over time the top RPM tends to drop. A couple hundred RPMs will reduce the engine horse power significantly. The manuals should tell you what the proper full throttle RPM is for the engine on the mill.

From Contributor E:
A good way to get a jump on the learning curve is to visit and help someone with the same or similar mill.

From the original questioner:
Thank you all for your help. It seems to mostly have just been a sharpness issue and poor alignment of the guide bearings also.

From Contributor F:
Call Woodmizer. They will give you all the help you need.

From Contributor G:
You must be a trusted friend. I have only one young man, 23 years old, brilliant kid, who listens. I allow him on the levers while I'm standing there but that's it. An LT 40 costs anywhere from $18-30,000 or more depending on the bells and whistles you order with it. With a hundred blades, a couple clutch inserts , spare drive belt, two extra sets of guide bearings and a used sharpener and setter, I've got well over $42,000.00 tied up in my Logmaster LM4 and that was 5 years ago.