grain directions with over-and-under jointer-planer combos

[Tim Romano]

I am a complete newb, and spatial reasoning sadly isn't one of my strengths -- my brain begins to chatter when I think about cutterhead rotation and blade angle and grain direction for more than a few seconds at a time. So I've drawn a diagram to help me ask the question.

I don't have an over-and-under combination jointer/planer yet but am considering one. The cutterhead of my old dedicated thicknessing planer spins counterclockwise. But the cutterhead of an over-and-under would spin clockwise, right?

So, when using an over-and-under jointer/planer with a board that has a chevron-grain, is the board jointed with the chevrons pointing at the cutterhead but thicknessed with the chevrons pointing away from the cutterhead?

[Chris Ricker]

Hey Tim;
Although I cant speak for all J/P combos, when using my Griz. in Jointer mode the work passes over the blades from right to left and when in Planer mode the work passes under the blade from left to right. The rotation of the cutter head is the same as in your sketch.
I hope this clears up any confusion.
CR

[J. Greg Jones]

Combo machines feed the opposite direction for planing operations than what they do for jointing operations, or stating it another way, you feed them from right to left to joint, left to right to plane. Just feed the grain direction the same way as what you do with your existing planer.

[Tim Romano]

Thanks for the clarifications. Left to right would work :-)

[Curt Harms]

Here's a demo if you're unfamiliar with J/P operation: http://www.jetwilton.com/us/manufacturing/en/product.html?node=4531&product=274240

[glenn bradley]

The directions of the cathedrals is only half the equation. Growth ring direction combined with cathedrals will get you there. Rings arching down on the example on the left. Rings arching up in the example on the right. Here's what I used to get my head straight on this:

[Tim Romano]

Thanks you guys for the link to the video and the growth ring diagram. That diagram raises a question.

The manual for my old craftsman 6" thickness planer describes how to plane boards that are wider than 6" by turning them around to send the unplaned half through. I have not tried this yet because I am trying to adjust the blades before I do any more work with it. But the approach, if I understand it correctly, would have you plane one half of the board face against the grain and one half of the face with the grain.

I don't have much experience to go on since I've only jointed and thicknessed two boards so far, one walnut one cherry, but judging from the litte I have seen, that approach might not be too bad with the walnut but I don't see how it would succeed with the cherry. The cherry seemed very easy to chew up because the grain had swirls. It got pockmarked near the swirls. Is the success or failure of the approach going to depend on the variety of wood and the specific grain characteristics? Do really sharp blades help minimize this pockmarking?

Also, can this reverse-the-board approach also be used on a jointer? Can you get decent results surface-planing a 9" board on a 6" jointer? I realize there would be some safety issues on the jointer, because the guard would have to be removed to do this