Please help! Unwanted tapered cuts on a new jointer.


I (finally) bought an 8" "General International" jointer but I've been having problems with my cuts; the work piece gets progressively narrower or thinner - I've been getting 1/32" - 3/64" per 7'. After most of a weekend working on this I am baffled. I understand that an outfeed table set too high can cause this. So I tried setting it at several levels, including one so low to the knives that it sniped at the end of the piece and still got a taper. I also tried to finesse it by bearing down harder at the start of the cut, then backing off on the pressure towards the end. This knocked off about 1/64" but still resulted in a taper. I've worked with a few industrial strength jointers in a wood class and in a mill but never seemed to have this kind of problem. Then again, I never measured the result quite so closely. Could I have done something wrong with the set-up? Is there some kind of flaw with the jointer? Or is 1/32" - 3/64" within normal tolerances?
I'd really appreciate any comments and suggestions.
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Check that the outfeed table isn't too high at the far end, meaning the two tables aren't parallel. That's the scenario that would result in a progressively deeper cut. Either shim the ways or return the unit.
This assumes that your technique is correct; transfer pressure to the outfeed table instead of bearing down on the infeed side as you joint your boards. You've used other units with no problem, so I think the tables aren't parallel.
Dave
spalted wrote:

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It really sounds like you are expecting the jointer to do what it was not designed to so. IF the board ends up with a curved edge or surface, the out feed table adjustment is probably the culprit. IF the edge or surface that you are running through the jointer is "straight and flat" after the pass regardless of how that edge or surface compares to the opposite surface or edge, it is working correctly. A jointer is not to be used to make parallel edges or surfaces. Opposite parallel edges and surfaces are acquired by using a table saw and thickness planer respectively.
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I didn't get from his post the same thing you did, Leon. What I got was that the jointer is making a tapered cut, which WILL happen either if the outfeed is too high (progressively SHALLOWER cut), or if the outfeed table isn't parallel, but sits high at the far end, in which case you'll get a progressively DEEPER cut. I agree you don't use a jointer to make parallel surfaces, but you also don't want the jointer to whittle away more of the wood from one end than the other, either!
Dave
Leon wrote:

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Too high, the board tends to have a convex bow on the side run through the cutter. Too low and the board tends to have a concave bow on the side run through the cutter. The out feed table is not used to create a taper.
or if the outfeed

It is almost impossible to prevent straight line taper on a jointer because the human hand does not provide a very good solid index constant like the table on a thickness planer or the fence on a TS. With lots of practice and fewer passes through the jointer you can keep the taper to a minimum. If the board is not straight to start with a taper is hard to avoid.
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because
and
This is why I usually make two light passes flipping the board end to end between passes. Mis-aligned tables will indeed result in curved edges, not "tapered but straight"
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That will help, IF the wood isn't tear-out prone in one direction.
Dave
TaskMule wrote:

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You're missing the point, Leon. The unavoidable slight taper you're talking about is on the order of a few thousandths of an inch over three or four feet, if the jointer is set up properly and the operator's technique is good.
The OP is seeing _an_order_of_magnitude_ more taper than that. 3/64" over seven feet is WAY TOO MUCH.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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Understood but maybe you missed the subtitle indicator that he gave,
" the work piece gets progressively narrower or thinner - I've been getting 1/32" - 3/64" per 7'. After most of a weekend working on this I am baffled.
If you run a piece through the jointer enough times it is going to add up and especially if you are a beginner on a board that is not straight. "The" work piece gets progressively narrower or thinner over most of the weekend. I read that as he has been going over and over and over on the same board.
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And I took it to mean that he's seeing that much taper on a _single_pass_ and has been trying all weekend to correct the problem - *not* that he's been running the *same* board through the jointer all weekend.
Perhaps the OP can clarify.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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Yeah, I think some pertinent details may have been left out.
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You are miles off tolerance. This is a common setup problem. Your manual should explain how to correct this. The input table and output tables are out of plane. The infeed table must be lower than the outfeed but still must be in same plane.
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============snip snip snip.========== Once I pass the blades almost all of the pressure I "put" downward on the board is on the outfeed table... almost nothing on the infeed side of the blades... But no matter how good your technique is if the tables are not co-planer... ya got problems...
Like others have noted . cutting on a taper suggests to me that your outfeed table is NOT co-planer to the infeed ...thus the end (of the outfeed) table may be slightly higher or lower then the leading edge of the outfeed table...
I have been using an old Rockwell jointer for close to 40 years and the outfeed table is fixed...no adjustments possible ..except maybe a machine shop... The first few months I had it I blamed the poor results on my newbie techique...Visited my Dad one weekend and I mentioned my problems and a quick visit to his shop proved my technique was ok... When I got home I had to shim the infeed table ....that adjustment held for over 20 years before I had to re-shim the infeed table,...
Honestly I do not know how badly I could have screwed it up if both tables were adjustable as most of them are,...
Lots of luck...
Bob Griffiths
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