jointing problem - rocker on long edges

[Steve]

While trying to edge joint some 55" and 65" boards on my 6" x 46" jointer I am regularly ending up with some rocker on the jointed edge. The infeed/outfeed tables are parallel as near as I can measure, same for the knives being equal in height to the outfeed table. I think I am keeping the board registered on the outfeed table.

I am starting with the bow side down, take a few 1/64-1/32" or so passes, the bow slowly goes away but by the time I get down to wood in the high zone, I seem to joint in some rocker - I'd rather have it be a spring joint. Once I have some rocker in the edge, I'd have to joint off a tremendous amount of wood to get back to flat.

I figure I am making a classic mistake of some sort or have something set up wrong that I am not thinking about. I'd sure appreciate some tips or help.

thanks,

Steve

[Swingman]

What I do in that situation, and I don't know if it is standard procedure but it works for me, is to joint (with almost no downward pressure) to the middle where the bow is most prominent, then lift the board off the jointer and flip it end to end and do the same until I finally get a pass over the blades that takes a full cut.

Worth a try in any event ... good luck.

[D Steck]

I used to have the same problem and after a few phone calls to discuss the problem, I figured out that it was all on how I transitioned my hands from the infeed to the outfeed tables. I wasn't maintaining pressure like I should have been. Since correcting that, I haven't had a problem.

[Mike O.]

I'm not sure if I understand the "bow side down". If you were to lay the board (on edge) on a flat table and see a gap in the middle, start your piece centered over the cutter and take a little off of one end then turn the piece around and take a little off the other end until you get the piece straight. If the bow is bad enough you may need to make one pass closer to the end and the another (on the same end) more towards the middle and repeat the same procedure on the other end. Make the final pass with the grain running in the correct direction after you've made the piece straight. If the problem is the other way where your board (on edge) will rock on a flat surface, start at one end and run to the middle of the piece, then turn the piece and run back to where your first cut stopped in the middle. Again, once the piece is straight, make your final pass with the grain running in the proper direction. If the piece is bowed (in either direction) you want to make the piece straight before you make full passes.

Mike O.

[George]

Yes, it is a classic mistake, so you have _lots_ of company. As Swingman says , the answer is to joint the high spots first.

You should always sight your board prior to jointing and attack the high spots. Normally I take the hollow side first, because it's where the sapwood is, and I don't care if I have a lot to remove. Then, as Mike says, the procedure is to run the ends before the entire.

It helps to make a couple of physical X's opposite the high corners of a twisted board when surfacing. Remind you that it's the left or right rear corner you're removing. My mental X's sometimes move to the other side when I reverse the board to take off the high corner.

[Tyke]

I too have suffered with imperfect edges when jointing long boards. I cannot determine if it is my technique to the jointer. Perhaps more of the former than the later. I gave up and if I need to joint a long board these days, I go one of two ways a) I clamp a straight edge to it and use my router. My straight edge is two 50inch sections so I can straighten up to 8 ft. I do this outside except in winter. b) I hand plane to take off the bumps and use my router table. This takes more setup than a) so I only do this in winter.

I have considered getting a jointer with a longer bed, since I think the

46inch bed is contributing to my technique problems.

Dave Paine.

[AAvK]

Concave side down. I have the same problem with the maple boards for my workbench, ripped to 2-1/4" depth (top-to-bottom) from 8/4 stock there is bending to about

3/32" to 1/8" deep because I "ripped too soon" (foolish me). The end jointing from the center is a good idea I had not though of (as Mr. newby) before.

What about simply wetting the boards, wet towel on top or wrapped and weighted with cynder blocks, convex on top? That way, I should think I would not lose thickness of the top (as completed) before handplaning to flatness. Would it work?

[George]

Nope. Once they dried, they'd return to the relaxed position.

[AAvK]

Okay... thank you... what if I do this anyway, and once flat remove the towels yet put the cinder blocks back on, leaving the wood to dry that way for a couple months? Would they spring back after that?

BTW this is some seriously hard, dense, heavy and very glassy smooth maple.

[George]

I've dried a few thousand feet of hard maple, and there's no way I know to bully it and get off scott free. I tried wedges on a stack inside frames like they did in an ancient FWW, beginning with green lumber rather than dry, and some still chose its own way when the wedges were released. After that, I just sticker, stack, and wait, not weight.

[AAvK]

like they did in an ancient FWW, beginning with green

released. After that, I just sticker, stack, and

Okay... and again, THANK YOU!... I think I will take mike O.'s technique. I have access to a monster 12" Oliver jointer which has a something like a 90 some-odd inch long table, and these boards of mine are around 60", that way would work perfect on it even if one direction would be going against the grain to do it (a very "iffy risk I think). After that, the Oliver planer for the convex side but I think I might get to 1-7/8" final thickness.

[AAvK]

Thanks for the technique Mike, I will use it but I don't know about that chopping against the grain, one never knows how much will get chopped off.

[John Girouard]

If I am understanding you right, I was seeing something very similar with my jointer a while back. It turned out that my outfeed table had a sag in it that no amount of technique could compensate for.

-John in NH