Jointer Problem

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Forum topic by azor posted 04-26-2009 05:54 AM 1494 views 0 times favorited 8 replies Add to Favorites Watch
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65 posts in 4003 days

04-26-2009 05:54 AM

Topic tags/keywords: jointer joining question oak

I have a 6” Jet jointer. I have been away for a few months and now it seems to have developed a problem. If I run a perfectly parallel board [red oak from Lowes] over it the jointer’s knives start cutting away for about half of the board and then any further cutting stops for the rest of the length. These are light cuts, about 1/32”. So I end up with a board narrower on one end than the other. Subsequent passes yield the same results. I put a 2’ carpenter’s level on both the in feed and out feed tables and both display a centered bubble. I am probably overlooking something simple, but cant figure out what I’m doing wrong or what is wrong with the jointer. Any suggestions?


-- It isn't as easy as the demos make it seem.

8 replies so far

View davidroberts's profile


1027 posts in 4045 days

#1 posted 04-26-2009 06:40 AM

just wondering, could the width of the board(s) vary over their length. i assume you are jointing the board, i.e. cutting the edge. a bubble level may not be accurate enough to see the difference in elevation from one end of the outfeed to the other. you may need to shim the outfeed table to get it level. over time the ends of the tables can dip just a hair. they don’t have to dip a 32nd to see a difference of a 32nd.

-- Better woodworking through old hand tools.

View Don K.'s profile

Don K.

1075 posts in 3886 days

#2 posted 04-26-2009 07:25 AM

I was thinking the same thing David, sounds like the out feed table may have dropped a bit. Take a Long level or straight edge,the longer the better, try to go past each end, but at least end to end, zero out both infeed and outfeed tables lay your level/staright edge across both tables and see if your outfeed table is dipped down a bit.

-- Don S.E. OK

View TomHintz's profile


207 posts in 3958 days

#3 posted 04-27-2009 10:21 AM

Is it possible that the board has a “crown” or arch that you have facing down? (Like a bowl sitting on a table) If so, it is easy to get it started on one side where it never will get to the other side where the crown (arch) runs up already. If you can find a piece of wood that is already pretty flat, try running that over the jointer a time or two to see if it continues to miss the last half or if it cuts all the way across.
I have had this problem with a badly crowned board. The only thing to do was to cut it in half and use it for smaller pieces in another project. Then, it worked fine. The best thing is to reduce the board to near the needed length and then joint it with the crown facing up (bowl upside down on a table) so you can take material off of both ends, perhaps reversing the board between cuts until it establishes a long enough straight edge to register on the outfeed table.

-- Tom Hintz,

View Boardman's profile


157 posts in 4321 days

#4 posted 04-27-2009 02:31 PM

For the life of me I can’t imagine how the table height on a jointer sitting idle for a few months could change all by itself. Or even a jointer used daily. The tables on a jointer are attached so securely that you could probably drop it from 10’ and not affect the table settings. But it seems that’s almost always blamed for jointing “problems.”

Azor – you mentioned the sides of the board are parallel, but didn’t say if there’s a bow in it. Sight down the length of the edge to see if there is. A bowed board should always be jointed with the concave side down. That way you’ll end up with it hitting the knives on both the leading and trailing ends, with no contact in the middle. DON’T put so much pressure on it that the center hits also. Use just enough pressure to keep it from hopping when it hits the knives. Each pass will take more off both the leading and trailing ends unti it eventually hits the knives in the middle too.

If you try jointing the convex side you’ll end up taking down only the leading end. Draw a “smile” on a piece of paper and you can envision how that would happen.

View miles125's profile


2180 posts in 4565 days

#5 posted 04-27-2009 03:37 PM

The bottom line is both beds have to be parallel with each other, not neccessarily level. Plus a bubble level has nowhere near the accuracy required to diagnose this. The surest test is a board remaining flat to the outfeed table after its cut by the blades. The factory set shims may indeed need to be tweaked if all height adjustment tweaking fails to work.

-- "The way to make a small fortune in woodworking- start with a large one"

View azor's profile


65 posts in 4003 days

#6 posted 04-27-2009 06:25 PM

Yes, even a bubble level 4’ long did not give me any new information. Yet when I apply a caliper to both ends before the jointing it reads the same width on both ends, the middle, etc. When I place the board on my saw table I don’t see any light in the middle of the edge.

Then I place it on the jointer and the first third or half gets cutting action and then stops for the rest of the board. The caliper now shows the board narrower on the end where the knives did some work, but no change on the rest of the board. I’m not much of a mechanic, but will see if I can spot some shims to adjust somehow. Wish I had a jointer plane to finish the job, however I am a real novice when it comes to using planes.

-- It isn't as easy as the demos make it seem.

View Julian's profile


884 posts in 4085 days

#7 posted 04-27-2009 07:52 PM

Try moving the fence to a different position. I had a similiar problem once, when my blades started to dull.

-- Julian, Homewood, IL

View azor's profile


65 posts in 4003 days

#8 posted 04-28-2009 08:20 AM


You’ve definitely have something there. I moved my fence in a couple of inches and then ran a couple of 2 foot boards over the cutters and there was contact the whole length of the boards. When I put the calipers on each end they were only different by 1/64 of an inch. I’m thinking that’s a great improvement over what I’ve been seeing. Thanks for the tip. Now I suppose I will have to learn how to sharpen the knives in the jointer. I guess that’s all a part of woodworking.


-- It isn't as easy as the demos make it seem.

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