Say,
I changed my knives on my 6 ” jointer a month or so ago, set all 3 baldes correctly etc. level with outfeed table.
Now when I joint edges there is a belly (slight concavity) in middle of board . hmm so I adjusted outfeed table a bit. Seems if the outfeed table is just a hair lower than the knives the board is jointed flat. i thought the knives needed to absolutley level with outfeed table.
What am I doing wrong here?
y
Replies
You aren't doing anything wrong, you can almost always improve the accuracy of a jointer by fine tuning the outfeed table height after installing new knives, that's the primary reason why manufacturers make the outfeed table adjustable.
Start with the outfeed table a bit low and edge joint two straight grained boards that are one half to two thirds the length of the jointer. Then place the freshly jointed edges of the two boards together and you will probably find that they gap and you have a snipe on the trailing edge of each board.
Now start raising the outfeed table by small increments and repeat the test until the boards match up perfectly. You start with the tables low because raising the tables takes out any free play in the table height adjusting screws.
If you have a lever adjusted outfeed table, it is hard or impossible to make this adjustment properly, never buy a machine with the outfeed table adjusted by a lever.
As the blades dull, or if you joint an especially hard or soft wood, you may find that you need to readjust the outfeed table to get the straightest edge possible.
Since the projection of the knives from the cutter head is set by the height of the outfeed table, which you have now slightly shifted, you will need to first set the height of the outfeed table according to the manufacturer's specifications the next time you change the knives.
John W.
I take a low tech approach to setting my jointer blades. My goal is to get the jointer to do it's job, if I do mine. I want the best quality cut I can get. If you don't get the cut you want, it doesn't matter what method you use to set the knives. The proof of success is in the cut and that is easy to check.
I never move my outfeed table. I think it's fairly easy to set your knives to it, rather than set it, to the knives. By using the outfeed table, I already know how far the knives should project from the cutterhead. I use a blade from a combination square. There seems to be something about it's size and weight that works well. Others use a piece of wood. Not very scientific but the results are what I'm looking for. I place the blade on the outfeed table and line up the 8" mark with the edge of the table. I roll the cutterhead and adjust the knife so that it moves the blade 1/8". Check each blade on both ends and in the middle. Once you have the knives set, do a short practice cut. Turn the power off again and use the short cut to check the fit to the outfeed table. The depth of the cut should land tight to the outfeed table. The jointer knives actually get set just a bit higher than the outfeed table.
Knives that have been ground on a machine are, often, not perfectly straight. Setting them evenly can be a compromise. I changed my knives last weekend and took some pictures. I sharpened the knives by hand on a diamond stone followed by a fine water stone. This gave me some nice straight blades to set up. These were brand new Freud knives so it took a little time to flatten them. From now on the sharpening will be easy. I don't get any visible knife marks with my set up unless I rush the feed
Beat it to fit / Paint it to match
Thanks for that detailed explanation. I've found my jointer's performance frustrating. I'd been making the knives perfectly even with the outfeed table because that's what I understood to be the correct tuning. Lo and behold, my jointer's performance is now MUCH better due to setting the outfeed table so that the knives are slightly higher. Thanks again.
P.S. In a separate thread over on the experts forum, I asked Ernie Connover for advice on my jointer frustrations, and the first thing he too suggested was trying some different outfeed table heights. So thanks to you both - just coincidence that the two threads yielded the same great advice at almost the same time, I guess. But wanted you to know that you and a FWW expert were on the same page.
The tables should reference off of the bottom of the cuts which are produced. So if you push a board very slowly across the cutterhead the outfeed table should be closer to the height of the knives and when you push a board fast across the cutter head it will produce cuts which are farther apart and the board will rise some across the outfeed table unless the outfeed table is set lower.
Theoretically if one could produce an infinite number of cuts close together then the outfeed table could be set even the with the top of the knives.
To produce a very nice cut the knives must be exactly the same height. This is done by jointing the knives with the machine running. If someone has not done this before it can be very dangerous. When doing this I use a very clean stone and set the outfeed table so that when the stone rests on the top of a piece of paper so the stone will not scratch the top of the outfeed table. Then I turn the cutterhead by hand so that the knives just tick the stone and I can hardly feel it while I hold the stone and push down on it. It is usually about .001" or slightly more. Once that is done then I turn on the machine with most of the stone resting on the outfeed table. Once the machine is running I carefully slide the stone resting on a piece of paper back and forth across the cutterhead. I repeat this process until all the knives are jointed. After each time I joint the knives I turn the machine off and check each knife to see if they have been jointed. Each knife should have a slight land on the top.
I can't understand how the jointer would cut anything after trying to cut a stone with them.
Ken
That is true if you joint too much off the tip of the knives. The objective is to get the knives at the same height. By doing so the jointer will produce very smooth cuts. You should be able to joint the knives about two or three times. When doing that it will actually sharpen them slightly.When the land that is produced when jointing is too wide it will not cut and cause the board to be lifted up.When the knives are jointed properly the jointer will produce better cuts and will stay sharp longer.
What kind of stone do you use, what grit?
Do you flatten it?
Thanks,
Ken
"Each knife should have a slight land on the top." I'm not familiar with the term "land" in this context. Could you clarify? Thanks!
I've seen the technique you described illustrated, somewhere, a couple place actually, but a little too scary for moi. Is there not a way to accomplish the same thing without actually turning on the motor? forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) Do unto others as you tell them they should do unto you....
Gee whizz I agree, I am not keen on doing it that way. Forestgirl, are your knives a smidgen higher than the outfeed table or dead on even?
A smidgen above. I use the test where you place a piece of stock on the tables and rotate by hand, getting the stock to move a bit with each knife-pass. (Thank you, Richard Jones, for emphasizing this issue enough to get me to try that approach)forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) Do unto others as you tell them they should do unto you....
"Each knife should have a slight land on the top." I'm not familiar with the term "land" in this context. Could you clarify? Thanks!A land would be like a flat area on the top edge of the knife creating in a sense a second bevel. I've seen the technique you described illustrated, somewhere, a couple place actually, but a little too scary for moi. Is there not a way to accomplish the same thing without actually turning on the motor? You could do it by hand but would take much longer. When I joint the knives I place the stone on top of a piece of notebook paper. When I am done jointing the knives they are the perfect height (about .003") above the outfeed table.
What kind of stone do you use, what grit?I use a medium diamond stone and place it just so it just hangs over the end of the outfeed table. Before I turn on the machine I make sure there are no problems by turning the head by hand. The knives should just very very lightly tick the stone.
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