Keeping Straight-Line Rip Saws Ripping Straight

Several odd tuning issues may cause your SLR saw to stray from the straight and narrow. June 28, 2006

Our shop has problems when we try to straight-line 4/4 lumber that is longer than 10'. The straight-line frequently tails off so the outbound board may be 7" wide on one end and 6 1/2-6 3/4" on the other. We're working with a SCMI M3 and a Nortek machine and we’re having the same problem with both so I suspect operator error. Does anyone have any suggestions?

Forum Responses
(Solid Wood Machining Forum)
From contributor R:
We have a laser on each of our gang ripsaws. We also have an in-feed table in front of each saw. One time, we had an operator who tried to align the beam of the laser with the edge of the board by "steering" the board as it went through the rip. He actually pushed the board left or right to align it with the laser once it was in motion and this caused the problem that you describe (at least it caused the problem for us). He did this because the board seemed to wander off the laser as the tractor pulled it through.

What was really happening is that long boards were rising up as they glided over the in-feed table and that changes the plane on which the laser draws the line. It was an optical illusion that he was reacting to. In any event, we taught the operator how to pull the in-feed table out from the saw to get a better balance on the longer boards, and we also taught him not to "correct" the board once it was in motion as it is pulled through.

I don't know if this is your problem, but our experience may give you some insight. Of course there are mechanical adjustments that you can make to your saws, but when you said that the problem exists on both saws I too suspected your operator - especially if the operator operates both saws.

From contributor C:
The most common cause of this problem is that the lumber is not properly conveyed behind the saw. It is imperative that the saw not have to push the lumber. A saw can usually push short lumber because there is not much weight and friction. But as the board gets longer, both weight and friction go up, and there is a point beyond which the board will lead off. The answer is to have a belt conveyor which is timed to run at the same speed or very slightly faster so that the board exits the saw with little or no "push".

From contributor G:

Lumber must be reasonably flat before ripping. We usually "skip plane" before ripping. If using roller tables, they must be exactly perpendicular to the saw blade. If not, the rollers will tug at the board and cause it to wonder off its line. The operator will naturally use his finger to help guide it. Flat infeed and outfeed tables are best. Use melamine board for a slick surface. A coat of wax wouldn't hurt either. Remember, you can't straight line cupped lumber – it must be fairly flat.