is it my jointer or me?

[kelLOGg]

I have a Makita 6" x 5' jointer which produces non-flat edges >:(. If I start taking off 1/16 inch of, say, a 5' board and after 3 feet has passed through the cutter head I notice the trailing 2 feet is off the infeed table, maybe 1/16 inch higher. At this point I can actually rock the board between the outfeed and infeed tables with the board pivoting at he outfeed edge . If I set the two tables at the same elevation and check for flatness with a 5' straightedge it shows they are perfectly flat as far as my eye can discern. If I drop the infeed table say 1/8 inch and check for level again the infeed table shows 1/8" air gap all its length. I do as best as I can to hold the board flat against the backplate and tables but I can't avoid the problem. Is this to be expected when edging a board longer than half the length of the jointer? The boards are not particularly heavy so the don't lift off the table.

[1938farmall]

the tables being parallel is a good thing.  now adjust the outfeed table to be tangent to the cutter head.  lay a straightedge on the outgeed table & over the cutterhead.  rotate the head by hand & lower the table until it just ticks the straightedge - then lock it.  maybe pull the plug before turning the head by hand.   al

[pigman]

Your outfeed table is too low. Do as 1938farmall says and you should be good.

[low_48]

Jointers can be tricky, but I'll try and walk you through it. I suspect the relation between the cutters and the outfeed table is off. The blade at top dead center should be a few thousandths above the outfeed table. Put a straight edge on the outfeed table, just past the cutterhead. Stay off the infeed. No rotate the cutterhead. It should lift the straightedge ever so slightly, and move it about an 1/8" forward till the straightedge drops back to the outfeed table. If it doesn't lift the straightedge, lower the outfeed table. Small adjustments are required here. Make a cut. If you go to far, and it now snipes the end of the board when it comes off the infeed table, raise the outfeed just till it no longer snipes.

Feeding the board correctly is important too. Site the board and run it so the crown is up, or to say that the board should have two point contact on the tables. Once the board gets about a foot past the cutter, keep you hands on the outfeed side only. Never have your hands on both sides of the head. It could possibly rock the board. The whole deal about the jointer, and it's accuracy, is the outfeed table. The infeed table is just there to set the depth of cut.

Hopefully that's clear enough. Good luck.

[kelLOGg]

If the outfeed table were low that would certainly explain it but it is tangent (as near as I can see) to the knife edges. My outfeed table is stationary so if any adjustment were to be made it would have be to the knives so I am now in the process of lowering them. I don't know how the wood is going to slide onto the outfeed table ??? ??? Maybe I'll get lucky.
Bob

[kelLOGg]

Well, I don't know what I did right but I got it. (Lowering the knives was bonkers of an idea as expected - that didn't do anything). I used lower48's technique of dragging the straightedge. I probably dragged it more than 1/8" but I adjusted all knives the same - slightly above the outfeed table. Ran one 5 footer thru and  8) the edge remained in contact with both tables all the way. I hope the results are consistent for all the rest of the boards. I quit for breakfast while I was ahead (hungry now).

I suppose "tricky" is the right word to describe it - I think the knives were adjusted from tangent to a few thousandths low and I am amazed the slight adjustment made the difference. ;D Thanks for the helpful replies.
Bob

[beenthere]

Surprised the outfeed table isn't adjustable.
But glad to hear you are getting the knives set at a good height. 
Just be sure to check each of them across the 6" width with the stick. I'd not go more than the 1/8" drag-back of the stick. Make marks at 1/8" apart on the stick to see the drag distance.

[kelLOGg]

I just finished edging 30 - 40 boards with success so I think I will leave well enough alone. The Makita planer/jointer is a small woodworker machine and doesn't have the capability of adjusting the outfeed presumably to keep cost down.