Wedge-Shaped Jointed Boards

[Mark Kristan]

I can't figure out why this is happening, nor can the people who sold me the jointer/planer help me. I'm a hobbyist and don't get to spend as much time as I'd like in my shop, the machine is made in Europe by a fairly reputable manufacturer, so I kinda suspect the problem is with something I'm doing wrong, but I can't figure out exactly what. I try to feed boards so that the blades cut in the direction of the grain, as per everything I have ever read on the subject. The problem is, if I make several jointing passes in one direction, trying to get the entire face jointed, I will end up with a much thinner leading edge than the trailing edge. I'll give you a specific example, today I was jointing basswood boards to make the apron for the underside of a computer desk I'm building for the bedroom. I have discovered that a fix seems to be to alternate the direction in which I feed boards but I guess I made too many passes in the same direction; a 50" board ended up about .4 inches thicker at one end, vs the other (.1" per foot, or so). I do tend to alternate the direction in which I feed boards in order to end up with more or less even cuts but this is supposed to be incorrect; I have observed that the end result seems to be fine and I will keep doing it that way for now, but does anyone have any thoughts on why I have this problem? I couldn't find any sort of instructions on how to set the machine up (and the dealer had nothing to offer in that regard) so I used it how it came out of the box. I have tried adjusting the amount of pressure I put (I tend to put just enough to slide the board) on the in/out -feed tables, to no avail.


Thanks,

Mark

[Jerry Miner]

I think your jointer beds are not quite co-planar. Check them with a known, good quality straight edge.

Dull blades can also have this effect as the workpiece tends to "ride up" on the knives without getting cut as you feed the work

[Richard McComas]

I believe you answer is here.
http://www.newwoodworker.com/jntrprobfxs.html


http://www.newwoodworker.com/jntrtaprs.html



+1 to dull blades, they do all kinds of weird things.

[pat warner]

Jointers flatten; they do not produce parallelism.
Subtle feed pressure changes manage the board's irregularities.
And those changes are enough to never produce parallelism.
Whether wasting one side or both, a stick finishing with uniform thickness from
end to end, is an accident.

[glenn bradley]

All good answers here. the basic answer is that jointers flatten, planers use that flat face to provide parallelism.

That being said, if your material is longer than your infeed table you want to be sure to provide additional support. The jointer is a simple machine that cuts relative to the infeed and outfeed table as a reference. If the material is not fully supported through the feed path many interesting things can occur.

Your problem is a taper and this is an example of an "arching" problem but, the impact of poor material support is demonstrated. When part of the material hangs below the table and rides up the edge of the table during the feed operation you can get non-flat cuts.

Bad jointer path-2.jpg

Think about that a moment and you can see how this fouls a proper feed path. This may not be your exact problem but, you get the idea of how important feed path regularity is to good results on a jointer. Roller stand, saw horses or whatever you normally use will do the job but, need to be adjusted to the proper height for the surface they are extending.

[Doug Herzberg]

What others have said: check your set up and make sure the knives are sharp. I've done the both directions thing, just watch the grain and make sure the last pass minimizes the tear out. You should be jointing one edge, then ripping with that edge against the fence on the TS to get the edges parallel. With a good quality blade on the saw, it may not be necessary to joint the board again. If it is, one or two light passes should take care of it.

[Mel Fulks]

I like Glenn's answer the best. Simpler and much more complete than the separate site one in regard to the climbing producing a concave arc. I add that is often done intentionally to make hollow glue joints. One or two thousandths is
enough to make a difference and some of the smaller machines are quite difficult to adjust regardless of operator skill level. Some vibrate so badly that the table can move itself when lock is removed. So you have to let motor come to full stop before undoing any table lock, a real pain. The large old machines can be retro fitted with a small pointer and marks filed on adjustment wheel that make one
thousandth increment movement easy.

[Chris Fournier]

If your machine is a combo jointer/planer make sure that the jointer tables are locked down! Sometimes I'll forget to do this on my combo machine and when I do I can joint wedges all day long. My jointer tables are spring assisted, yours may not be.

Also check to see how high the knives are in relation to your out feed table, I like mine to be .004" or so higher than the table. I'm in SW Ontario as well, feel free to PM me if you want to discuss this further or you would like to drop by for a quick little demo.

[peter gagliardi]

Blades are dull, or outfeed is too high. Jointers are simple machines, and , therefore diagnosing issues is as well.

[Marty Tippin]

There was a nearly identical thread about a month ago.

Bottom line is that a jointer's job is not to produce board of consistent thickness - that's the job of the planer.

[Lee Schierer]

It could be your technique. As soon as the leading end of the board has enough material on the out feed table to get a grip you should transfer your down pressure to the out feed side of the cutter head. Your trailing hand should only hold the piece against the fence and push it through the cut. No down pressure.

Also, don't try trimming a board width more than about 1/8". If you need more taken off, use your rip set up on your table saw.