How to Eliminate Joiner Tear-out?

How to Eliminate Joiner Tear-out?

I have tried several times now to get a good straight edge on a board of maple using my joiner, but even though I have brand new knives, they keep taking chunks out of the wood. My router seems to do the same thing on maple. What can I do?

Lee Grindinger: Maple is tough because of wavy grain. Often there is no right direction to pass a maple board through a jointer. Make sure your knives are sharp and all set within a thousandth or two of each other. Your feed rate should be slow and depth of cut should be set very shallow. The router gives you the option of climb cutting and this should work to eliminate the tear-out you’re having problems with. Again, make sure the cutter is sharp.

Rob Johnstone: Wood will “chunk-out” for a number of reasons and maple is one of the worst culprits in this regard. What’s actually happening is that the wood is fracturing or tearing rather than being sliced or cut. There are several reasons why this occurs, but the simple response is to reduce the amount of wood you are cutting off with each pass. Equally important is the idea of “cutting with the grain”. The fibers in the tissue of the wood are more easily cut or sliced when you are moving the cutting edge thought the wood in a favorable direction (with the grain). I’m sure you’ve observed this. If you take the time to carefully examine the flow of the grain in the stock you are routing or joining, after a while you will learn to identify “trouble spots”. Some wood, bird’s-eye maple for example, is almost impossible to machine without tear-out occurring. But again, remember the concept of removing as small an amount of wood as possible per operation and you will be on the right track.

Simon Watts: It sounds as if you are trying to make too heavy a cut or feeding the stock too fast — or maybe your timber is what old world cabinet-makers called ‘spiteful.’ Try this: lay a straight edge on the rear table (outfeed) and check that each knife just grazes it. Do this on both sides of the cutterhead. If one or more knives are too high (or low), reset them.

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