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My Jet 6" Long Bed Jointer is driving me nuts, I have checked out a lot of YouTube videos on the subject and, as best I can tell, my jointer setup is correct. Its infeed and outfeed tables are parallel and the blades are set just a touch higher than the outfeed table. The problem is that no matter how many times I feed a board through the jointer, it doesn't get any flatter. In fact, it gets worse. My technique is to hold the leading edge down very lightly at the start and then increase the pressure after the first few inches of the board have been jointed. This seems to lift up the back end of the board and I wind up with a bowed rather than a straight board. I don't remember having this problem with my previous jointer, leading me to think that it is a setup problem. On the other hand, it has been a while since I have used a jointer so maybe I am doing something differently. Any constructive suggestions would be appreciated.
 

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Your outfeed table and blades need to be flush. Your infeed table moves to the depth that you want jointed.

Once our outfeed table is set to the blades you should almost never have to change it unless you switch blades out.

Paul
 

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I've done the same thing it is a matter of technique I think. Your probably pressing to far forward, if the rear starts to lift when you press down move further back from the front till it stops lifting make that your pressure point and after it passes over the blades then transfer the pressure over the out feed table.
 

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When are you applying pressure to the leading edge? The pressure to this edge should not be applied until it has cleared the cutter head by approx 4" or so. Are you applying pressure to this edge while it directly over the cutter head?

You might want to post a short video of your technique so we can all have a look (might make for a good learning experience and discussion for all).
 

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Thanks to everyone for your input. Per question from Targa, I lowered the infeed table, placed a steel rule on the outfeed table and then rotated the cutter head by hand. One YouTube video that I watched said that ideally, the blade will touch the rule and move it toward the infeed table 1/8" each time a blade rotates over the top. Assuming that it is correct, I like this criterion because it uses commonly available equipment. My calculator says that this equates to the blade being .002" above the outfeed table.

After fiddling with the outfeed table in both directions and making more sawdust, I am inclined to return it to its original position, which was very close to the 1/8" criterion, and work on my technique.. I am also going to wax both tables to decrease the sliding resistance.

Here is a followup question: The advice that I have seen says to joint with the bow side of the board up. What do you do if you are edge jointing and both edges are irregular?
 

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It sounds like the set up is correct so it's probably a matter of technique. When jointing an edge I always want the crown to be up and then start by taking short passes on each end until the board is sitting flat on the jointer bed. Next I will take a couple of light passes over the length of the board then rip the other side off on the table saw to get two parallel straight edges. If you start with the crown down the board will have a tendency to rock as you pass it over the knives and you will just keep repeating the error no matter how many passes you take.
 

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When I'm setting my knives I set them so that as I turn the cutter head by hand it slides the rule forward about an 1/8 like you said. Once I have all 3 knives set this way, then I set the out feed so that the knives just kiss the rule and don't even move it. I joint with the crown up or concave side down. If there is a great bow, I will either run one end thru and lift off a few times til it's straighter or use a hand plane on each end first. What I have trouble with is warped boards and trying to make them flat. If both sides are concave, then it doesn't matter. You just need one side jointed and then run it thru the table saw.
 

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I agree your set up sounds right.

I had a similar problem with my new Grizzly jointer. By lowering the out feed table so the blades at TDC were a couple of thousands higher than the table solved my problem. Its amazing that such small changes can make such a difference with the results.

Try working on your technique and if that doesn't take care of it, I'd try lowering the out feed table a touch more. Btw, I believe Powermatic's owners manual describes a set up procedure similar to what you did but may suggest the right blade height is achieved when rotating the cutter head manually moves a steel ruler by 1/4".

Please report back how you make out.
 

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You set it a touch higher with fresh knives. If they've been used a fair bit while adjusting set them flush. If they're set to high you will have a slight crown in the middle.
 

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Discussion Starter · #13 ·
Again, thanks for all of your comments and informative links. I think that at this point I have enough information to write a book on the subject. I just finished another round of adjustments that resulted in moving the steel rule a little less than 1/8", waxed the table and the guide and gave it a try using moderate pressure on the infeed table throughout the pass and moderate pressure on the outfeed siide once I had the board partway through. I took about a 1/32" pass and everything seemed to be good.

BTW - I think I remember Norm saying that he usually jointed one edge, cut to final width on the table saw + 1/32" and then finished the cut edge with a pass through the jointer. Basically, he just always left his jointer set to 1/32". Seems pretty reasonable to me.

Also BTW - The impetus for this activity was a table top glued up from several boards that got wet during a minor flood in my garage and then left for way too long. The result was that the table top split and the only way to fix it was to cut it apart, straighten the edges where the split occurred and then glue it back together. Moral - Don't let projects sit around for too long because wood moves and accidents happen.
 

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I bought a jointer thinking the knives would be set correctly. WRONG! The problem sounded very much like yours. I finally found knife #1 would be set low on the fence end and knife #2 would be low on the outboard end etc. When I corrected this and set the jointer like you describe it worked fine. I was ready to buy a boat because I thought I had the anchor. Worked fine for 30 years now.
 

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gfadvm, my jointer would make a concave into a convex and short order. I was really frustrated. I final found an old hardback book I had on shop tool maintenance and I got the knife problem fixed. Then my jointer worked like it should. I had made the wrong assumption that the knives would be set from the factory and I could use it as delivered.
 

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I bought mine used and the knives were way off. It came with some sort of guide for setting the knives. I never tried it, but it must have been junk if the guy before me used it. After I reset the knives it worked great.
 
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