Tear-Out Problem When Machining Flooring Ends

Ideas for stopping the wood from tearing out when the cutters get close to the edge. November 27, 2007

We are trying to end match pine flooring on a double end tenoner. The boards are previously tongue and grooved on the edges by a molder. Up to several inches of the edge tongues are torn off when the boards come out of the tenoner. We have slowed the tenoner feed speed down to the minimum and gotten no improvement. Would appreciate any suggestions.

Forum Responses
From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
This is a common problem. One solution is to machine halfway in one direction and then reverse the piece and go the other direction. This means you will not be machining the edge and give it a chance to split out instead of being cut off. Of course, you will have to use a router, spindle shaper, or other similar machine, and not a DET.

As you get close to the end of the cut, the wood asks itself if it is easier to be cut off or if it is easier to split off. The question you might ask is why there is so much force trying to cut the wood, so that splitting is easier? Is the tool sharp (HSS rather than carbide), with a small amount of stock removal, including shallow cut (several passes)? Also ask if the wood over-dried (under 6% MC) so that it has become brittle and is easier to split than to cut.

As a last resort, some people will glue a temporary block on the exit edge to help hold the wood together and avoid exiting in the work piece. Any exit splits would be in this temporary piece.

From the original questioner:
Thanks, Gene, but a double end tenoner seems to be the most practical for us, producing several trailer loads of flooring per run. Anybody out there have ideas on how to end match flooring on a double end tenoner? Any recommendations on the angle of the knife in the head and the cutting angle on the knives?

From contributor S:

Doesn't a DET have backup blocks mounted on the feed chain? The ones I've seen have nylon backup blocks which would greatly minimize tearout.

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Contributor S is correct that some DET machines will be equipped with backing blocks to keep pressure on the ends to prevent chipping or splitting.

From contributor J:
Pack multiple boards in front of your dogs - as many as you can fit. Pull back against the dogs until the first board goes under the upper pressure pads. The multiple boards will prevent the tearing. For the last one against the dog, I would insert a sacrifice ripping, same thickness, and carrying a groove or tongue. You might have to stop the feed chain. Which spindles are you using, cope or tenon?