Edger Causing Crook in Boards

      Sawmill operators discuss what could cause an edger to send boards off track. June 28, 2010

Question
We are having problems with our edger hooking or causing crook in boards when going through the machine. Has anyone else ever had this problem? They appear to run through straight, but come out crooked almost every time. The longer they are, the worse it seems to be.

Forum Responses
(Sawing and Drying Forum)
From contributor R:
Not on a Wood-Mizer, but I've seen this problem in other edgers when one blade is significantly duller than the other... It pulls the lumber. This happened in my case from edging a lot of one sided flitches over time, and that one blade dulling quicker than the other. I probably had more than double the sawlines on one blade than the other.



From the original questioner:
Thanks for the response. First we tried slowing the machine down and it was still pulling, so we changed the blades to see if it was a blade problem. That's not it either. We pulled the bearing off the moveable saw and repacked it with grease because there was a little slop in it. That didn't work either. Wood-Mizer doesn't seem to know anything about their edgers, so they haven't been able to help us either. I don't know if this is a problem that they just have with the diesel model or what.


From contributor S:
My guess is that you have stress in the log. Sounds like your machine checked out if putting on new saw blades did not have any effect. You could try swapping sides with the blades. I just finished making a Western red alder dining room table. I found that on some of the boards I could run the board through the jointer to achieve one straight side, then table saw the width I needed. Afterwards some of the boards would be crowned (yes, even the side that went through the joiner and straightened was not straight anymore). Try a different batch of logs.


From contributor A:
I have two WM edgers. One is gas and the other is electric. RPM's will affect the cut of the blades. Also the blades can lose their temper just like big saw blades and have to be re-hammered. I had to have the blades on my gas one re-hammered to 3,000 rpm and they cut well now.

Also the grind on the teeth make a difference. They should all be a straight grind across the teeth. Once mine were ground like a table saw with angles and it edged poorly. Your bearings can move out of alignment from the feed rollers to the blades. It mostly causes the boards to move to the side.

Since longer boards cause more problems, I would look at tension in the blades. The more they heat up, the more they deflect and cut wrong. If you hang up fletchings in there, it can overheat the blades and make them lose tension. Or your teeth are not wide enough to give you good side clearance.



From the original questioner:
Thanks for the response. How do you check to see if the blade has lost its temper? Or do I need to take it to our filer and have him check it? What exactly do you mean by the teeth may not be wide enough for good clearance? I will check to see how they were ground. I'm pretty sure they're okay though. Our filer has been sharpening circle saws for 25 to 30 years.


From Professor Gene Wengert, forum technical advisor:
Draw a straight line lengthwise on a piece of lumber, then edge it. If the piece is now crooked, check the straight line and see if the line is still straight (indicating a machine problem, probably feed rolls not at 90 degrees to saws or similar). If the line is crooked, then you have stress in the wood; it is called growth stress as the stress developed during the trees' growth.

Can you try to edge by ripping one cut down the middle of the piece? If growth stress, then you will have two pieces that will not fit back together tightly, but there will be a large gap between them.



From contributor B:
Remove the blades and run some boards through the edger. If they go through straight without the blades, the blades are the problem. If the boards still turn to the side, the feed rolls are the problem.


From Professor Gene Wengert, forum technical advisor:
Contributor B is correct only if there are no growth stresses.

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