Illogical Jointer Set-up

I am confused with my 6″ jointer set up. I own an 80s vintage Taiwan import from a company that subsequently went out of business. I recently pulled the blades out for sharpening. I took lots of time and care to install all three blades the same distance from the out-feed table. This I confirmed with feeler gauges. Using a machinist square that I’d verified as being square (the old flip it over and draw another line technique), I set the fence exactly 90 degrees to the in-feed table. I then test joined some edges. They were not close to being square to the surface. The face against the fence had been surfaced first on the same jointer set up. I had to deliberately set the fence to less than 90 degrees in order to get a right angle edge. There is an obvious gap at the bottom of the square now in order to get a square edge to the face. I’m getting a satisfactory result now but it took a lot of time and seemed to defy logic. I would appreciate any insights you could offer.

Michael Dresdner: Let’s see if I have this right. You set the blades of the jointer level to the outfeed table, and the fence at 90 degrees to the in-feed table, and it doesn’t cut square. Offhand, I would say the in-feed and outfeed tables are not in the same plane. One quick way to check that is to set the fence square to the in-feed table, then read it relative to the outfeed table. Another is to use “winding sticks.” At any rate, I think you know what you need to do: shim the outfeed table so that it is in the same plane as the in-feed table, then reset the blades, and reset the fence. Why shim the outfeed table instead of the in-feed? Because the in-feed table moves far more often, as it is used to set the height of cut, and movement is likely to wear or dislocate shims.

Ellis Walentine: I’m not sure what you mean by “the same distance from the outfeed table,” but that could be the problem. You want all the knives set so that at top dead center they are equal to or ever so slightly higher than the outfeed table all the way across. If that is what you did, and you set the fence square to the outfeed table, there aren’t many other possible causes for the results you describe. One possible explanation is that your fence is warped. This is not uncommon, especially on less expensive jointers, and it could tip your board slightly at either the in-feed or the outfeed side of the cutter head. I’d check it out carefully and have it machined flat if that is the problem.

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