Jointer help needed

I am in need of some serious help with my jointer. For the life of me I can not seem to get a board to come out straight. I'm not sure if it's my technique or if it is the setup of the jointer. Yesterday I had a board that was 19" long that was slightly convex on the edge that I needed to be straight. After making a couple of passes across the jointer, the edge of the board was worse than when I started. I turned the board around and made two more passes at which point I determined if I kept going I was going to end up with a "V" shaped board. I can take a 2' board that is straight except for the last two inches, and by the time I'm done, it will only be straight for the first 12 inches.
Tonight I took a 14" machinist square and tried to verified that the infeed table was parallel with the outfeed table. It is as best I can tell. I took another board that was slightly convex and made a series of passes marking the edge with a pencil before each pass so I could see exactly where material was being removed. It appears that with each pass I remove less and less material. On the first pass I might get a cut on 90% of the edge, on the second 75%, etc... The fourth pass thru will only cut from the leading edge to the middle of the board.
Any help to 'straighten' out this mess would be appreciated.
Mark
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wrote:

sounds like your outfeed table is low.
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Low in relationship to what? The knives? The infeed table?
Mark
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wrote:

the knives.
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I thought if the outfeed table was too low it would cause snipe on the end of the board. In my case I can pass the board through the jointer and it doesn't cut the last inch or so of the board.
Mark

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mark,
when i first started using my jointer, i experienced similar problems ... and similar frustrations. now, with some experience, i can tune it quickly. here's what i do...
first of all, make sure your knives are at the same height. i haven't found a fast way to do this (advice anyone?) so i just use a magnetic base dial indicator (grizzly, cheap). anyway, this takes a LONG time to get right, no less than an hour. maybe i'm just slow.
what i do to get a flat cut is actually trial and error. i start with the outfeed table a little too high so that the wood catches as you feed it, and i lower it a little bit at a time until the board joints straight. i joint two long-ish (24" or so) boards and stick them edge to edge, look for gaps. i basically keep adjusting until they meet cleanly. takes about 5 minutes.
that works for me. is it perfect technique? no clue. seems to work ok.
--- dz
Mark Jacobs wrote:

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On setting the knives in a jointer, I've tried many methods, and found the dial indicator is the best, taking maybe ten minutes for three knives. I had the same frustration using a magnetic base, and the key is the technique.
First, the dial indicator set up must be fast and easy. A magnetic base with elbow arms takes awhile to fuss into place, and longer to iterate measurements. I have a 2x4" piece of melamine I place on the outfeed table. A rail projects out a few inches, and the dial indicator mounts on the end, so I just tighten the rail and then zero the indicator against the outfeed table.
I put the knives into place, using two short wood strips to press them down about even with the table. The wood won't damage the edge, and this takes them within about .010 and slightly high.
Due to the fixture, I only have to slide the block around to move the dial indicator to each end of the knife. When I'm close, I use one of the wood strips and a light mallet to gently tap it to zero. It's easy to make sure you're measuring at the right point, by just rotating until you see max on a knife edge. You might also look around for dial indicator tip sets, to find one that's easier to use here.
The same fixture, by spanning the knives, lets you set the infeed table dead even with the outfeed, Do this at one side, swivel to check your outfeed flatness, then move to the other side to see if the beds are parallel.
This does not, of course, check over the length of the bed. Another technique is needed for that.
GerryG
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A magnetic base works much better if you place a steel block under it, such as a 1-2-3 block, the magnet will hold every thing together, and you can slide the assembly across the table.
GerryG wrote:

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rick -- interesting - elaborate on this please - so you still put the dial indicator on the arm of the magnetic base, but you stick the base on a 1-2-3 block? why - to give yourself a reference to align to edge of the table?
i really do need to find a better way to set my blades, if you could elaborate a bit i'd appreciate it. i'm kind of dense and need it spelled out.
thanks very much,
--- dz
Rick Samuel wrote:

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Sure, adding a steel block will reduce the pull and allow you to slide it. Provided, of course, you don't put fine scratches in the table. (Actually, that old trick includes masking tape on the bottom to prevent scratches.) More than that, however, the issue's with the standard elbow arms for the indicator. Try repeating the same measurement several times, going back and forth from one side of the table to the other. How close do they repeat? Brush it just a bit with your arm while moving it, and how much does it move? And if you've got one of the cheap sets, how long did it take to get the elbow arms adjusted and tight enough?
Of course, IF you can quickly set that up, and IF you can repeat the same measurement +/-0.0015, THEN you're doing fine so just keep going that way.
I use the same set up I described before for squaring other tools, including the BS, drill press and router table fence. I also have a mag dial indicator base and arm and I do make use of it, but only for those types of measurements that it was designed to make.
GerryG

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I experienced similar results a couple weekends ago. What I found when I took a straightedge to my outfeed table is that it is not flat - it curves up the further it gets from the knives. Sigh. I'm going to try to take it to a machinist and see what he can do. I'm pretty sure the jointer is out of warranty - it is a 1952 4" Craftsman.
-John
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