Unnecessary jointer shimming


Recently, any time I tried to flatten one side of a board, my jointer would start the cut OK but would remove less wood on the last 2/3 of the board. Eventually my board was wedge-shaped with the front edge narrower than the rear. I knew this is caused by the infeed and outfeed tables not being parallel. To get a true read on how much they are off you need to use a perfect straightedge the length of both tables. A good method of making a straight "test bar" is in Fine Woodworking issue 142. I checked all the other adjustments, blade height, gib screws, table height, etc, and they were all OK. I was going to shim my outfeed but I was puzzled as to how two perfectly flat tables can go out of parallel. After all, how much wear can occur in the gib and dovetail areas from the minor amount of table height adjusting done on a normal basis? Instead, I removed both of the tables and cleaned the gibs and dovetail areas. I reassembled and tested. It worked perfectly. Something, most likely sawdust, must have built up in the top edges of the dovetails to cause the out of parallel condition. Shimming the table would have also fixed the problem but all I would have been doing was compensating for dirty gib/dovetails.
Dave
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This is not uncommon, even with a well setup jointer. Despite the "wedge" shape, was the jointed surface of the board flat?
If so, that's all you can expect from the jointer.
To get rid of the wedge shape, and make the opposite surface/edge parallel to the jointed surface/edge, enter a planer for the surfaces, and the well setup table saw/fence for edges.
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I agree that a slight wedge shape can be normal while flattening one side. But this was extreme. By the time I surfaced one side I had already lost over 1/4" of a 4/4" board. After the first few passes I knew something was wrong. There are times when shims are the only way to make the tables parallel. The purpose of my post was to alert guys that you might want to clean the dovetails before shimming. Swingman wrote:

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That can also happen when your outfeed table is slightly above your blade height.
bc
snipped-for-privacy@aol.com wrote:

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Thanks for the post, Dave. I just purchased a used 8" jointer, and removed the infeed table for transport (and weight reduction). I'll be cleaning up the ways and gibs before reattaching (may or may not remove the outfeed table ...)
I was doing some edge jointing on my router table a month or so ago was getting this same behaviour - wedge shape forming. Turns out the two faces of my fence weren't perfectly coplaner because there was the slightest bit of schmutz (sp?) on the shim stock for the outfeed fence face.
Regards, Chris
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On 1 Mar 2006 05:08:27 -0800, snipped-for-privacy@aol.com wrote:

Petty common maintenance issue especially with a lot of use.

Assuming a quality machine to start with, it would take a lot of moving of the tables to wear out the dovetails. I've seen 50 year old joiners, that once cleaned up, have tables that are still quite good to each other.
Mike O.
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There is a book out by the shop foreman for FWW. The title is something like "setting up 5 basic power machines". I took it out at the local library. His section on the jointer would be worth purchasing the book. I had shimmed and diddled with my old 6" Rockwell until it was unusable. I used his directions, took the machine apart and cleaned and reassembled as per his suggestions. It is running absolutely great. Would highly recommend. ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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