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I have an older delta model jointer, and I always struggle to get all three knives consistently set at the same height.

I've tried a large magnetic jig that purports to help, but.. it really doesn't- it gets in the way of tightening down the nuts that hold the knife in place, so the knife tends to move when you slide the magnet out of place (or you bump it with the wrench and have to start over.)

I've also tried the distance per rotation thing with a piece of tape and a straight edge, but it becomes hard to keep the front and back side of the blade at the same height that way (they tend to rock in the middle.)

Anyone have tips or a jig to help keep your planer knives lined up?

  • there is nothing pushing against the back of the knives? – ratchet freak Apr 14 '15 at 20:14
  • On this model, there's a small blade carrier with three bolts that wedge the blade in place. – TX Turner Apr 14 '15 at 20:32
  • no springs or jackscrews behind the blade that push them out of the head? (or hole where springs would go if they were there) – ratchet freak Apr 14 '15 at 20:34
  • You mean under the blade to push them up? No. The carrier and blade are free floating in a U shaped channel on the cutter head. – TX Turner Apr 14 '15 at 20:39
  • I would like to know the length of the springs and their possibly diameter in millimeters, has a similar machine but I no longer have the springs, so I could use this data. Thank you for your cooperation I cordially greet Pierluigi – user1152 Sep 18 '15 at 18:30
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This article has a nice tutorial about how to set the jointer knives.

It covers 2 styles of heads.

First is the style with jackscrews (labeled A in the image):

enter image description here

With those you can adjust each screw until the blade is set correctly (as with the straightedge method).

The second style is the one with pushback springs.

enter image description here

With those there should also be a jig you hold against the head that holds the knives at the right height and provides enough space for you to tighten the screws.

enter image description here
all images from the linked article

  • Yes, both these methods rely on the 'drag a straight edge a certain amount' method (I wasn't clear when I called it "distance per rotation". With my jointer this is a 2-3 hour process because the act of tightening one screw will likely move the other end and vice-versa. Ah well, my quest for the perfect knife setting gadget/jig continues. – TX Turner Apr 14 '15 at 21:47
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    @TXTurner actually the second relies on a jig that holds the blade in place while you tighten. and the drag straight edge is used to verify/set the outfeed table. – ratchet freak Apr 14 '15 at 22:58
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There are a number of tricks for setting these. One I've seen: put a piece of wood across the outfeed table and the head, hand-rotate the head, mark how far the wood was dragged by a single blade, adjust until they all drag it the same distance, repeat for other end of blade, iterate. Or of course you can get a dial indicator. Or build/buy a magnetic jig that holds blade at a known location until you can lock it in. Or ... Haven't tried to compare these so I have no idea about relative accuracy vs hassle vs price.

  • Yup, the 'drag a straight edge X distance' is what I use right now-- tends to be a long process because tightening one bolt seems to move the knife. Becomes.. 'tighten.. measure.. loosen.. move.. tighten.. measure.. loosen..' -- lather, rinse, repeat. I have one magnetic jig, but the 'arms' of it get in the way of a wrench. Maybe I can make something myself. – TX Turner Apr 14 '15 at 21:54
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I have an old Delta like that, too.

What I do is raise one blade up a few millimeters and loosen the bolts a bit, then place a flat hardwood board over outfeed table and push down. Next I rotate the cutter head backwards so that the blade get pushed down by the board, and apply pressure until it's the right height. I check the result using the straightedge method. It usually takes a few attempts to get all 3 blades aligned.

Bolt torque is really important with this method, so try to loosen the bolts very precisely. The difference between "too tight" and "too loose" is really only a few degrees.

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