Jointer cutter head lock mod #1: Modify cutter head so it can be locked when adjusting knives

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Blog entry by ic3ss posted 05-21-2012 04:53 AM 4056 reads 2 times favorited 2 comments Add to Favorites Watch
no previous part Part 1 of Jointer cutter head lock mod series Part 2: Two more holes, then try it out »

Well I’ve had this old jointer for a little over a year now and have had to pull the knives for sharpening a couple of times already because of damaged edges. I have to be more careful I guess. I’ve read all about how to adjust the knives, it’s really pretty simple concept but it’s not that easy sometimes to get the damn things even from one end to the other, and all three knives the same. The main problems I’ve identified are these:

Moving a dial indicator around to measure both ends of the knife is a pain and possibly inaccurate. To resolve this I bought a jointer pal jig. We’ve all seen these, it’s a pretty popular jig. But one more thing still keeps me from being able to set the three knives with real ease, and that’s the fact that this jointer and all of the others out there that are the same basic design have no way to lock the cutter head with all three knives in turn at top dead center. We’re forced to bang a wedge in there to hold it, which I really don’t like the idea of, or worse yet to hold the thing with our fingers. I know I’m not the only one who’s cut a finger in this pursuit. It’s just a stupid omission in design that should have been addressed a very long time ago. And as of this weekend, I’ve had enough.

After failing to find any mods that have been done for this problem on the web, I came up with my own idea. I would get a pin at about 1/4” diameter and drill a hole in the front bearing housing and all the way into the cutter head to lock it. It would have three holes in the cutter head located exactly the same in relation to each knife. Simple.

First I had to take out the cutter head and remove the bearing housing, then locate and scribe a centerline on the end of the housing that continued across the flat top part. The lines are in the pictures but not that easy to see. I forgot to get a picture when I was making the lines.

Then I had a problem to avoid. On the bearing housing there is a threaded screw hole that comes up from the bottom. The problem is that this was the perfect place for the pin, so now I had to have the pin on one side of this screw hole and that meant it would be very close to one of the knife recesses and the screw hole. There’s just not a lot of room. So I had to be precise, so I drew lines on the cutter head where the screw hole sides were, this was one boundary that the pin hole couldn’t cross and I had to leave enough metal in-between so as to not compromise the threaded hole’s integrity. To draw these lines I had put the bearing housing barely on the bearing and lined up the flat top’s scribe mark with where the top knife edge was, then extend the screw hole lines down onto the cutter head below the bearing. I also at this time put lines for the edges of the screw hole on to the outside of the bearing housing. Then I had to transfer the edge of the knife recess onto the bearing housing using a straight edge. In short, I had to draw the boundaries of the screw hole and the knife recess on the side of the bearing housing so I could see where it was safe to locate the pin. Once I had my boundary, I put my pin down on the bearing housing to decide where to locate it, marking it with a punch. Here are the marks showing where I located my pin hole.

Then I drilled the bearing housing on the drill press.

Then showing the completed bearing housing.

This is the bearing side of the housing. I had to also be careful to put the pin hole far enough away from both the bearing recess and the outside surface of the housing. I pretty much nailed it in the middle.

This picture shows me putting the pin through the bearing housing and the pin touches down on the cutter head. If your line extensions were drawn right, there should be enough metal between the pin and the knife recess, and the pin and the outside edge of the cutter head. Where the knife recess is concerned, you can see where the screws of the knife lock bar push against the recess. We’re not drilling that deep into the cutter head so there’s no concern for the lock bar deforming the metal into the pin hole. I only drilled about 1/4” deep.

With the bearing housing FULLY seated on the bearing, I used the new hole as a bit guide and drilled into the cutter head. I rotated the housing with the bit sitting on the cutter head until I was satisfied I was aligned with top knife edge and scribe mark on housing flat, and the bit was far enough away from the knife recess that I was comfortable.

Here I have the pin (or drill bit) far enough from the knife recess edge.

And here I’m lined up with the flat scribe mark and the knife edge. When I’m doing this, I removed two of the knives, leaving one so I can line it up with the scribe mark. The other two recesses are empty, so when I refer to the knife recess, I mean the next one clockwise from the top. Just FYI.

Here I have started the drilling but it’s not very deep yet. You can see how far away from the knife recess it is. I drilled down exactly 0.225”. It doesn’t need to be very deep, and too deep could cause a problem with the knife lock bar as described above.

The pin fully inserted into the cutter head. Because I left the bearing housing on as a guide, the pin goes in with no catches, nice and smooth.

Lastly, I started making a jig at the end of today so I could drill the next two holes in the cutter head at exactly the same place relative to each of the remaining two knives. It’s gluing up as I’m typing this, so I’ll update this tomorrow.

Let me know what you think. Good, bad, whatever. See ya tomorrow.


-- "I am endeavoring, ma'am, to construct a mnemonic memory circuit using stone knives and bear skins."

2 comments so far

View gfadvm's profile


14940 posts in 4026 days

#1 posted 05-22-2012 01:37 AM

That looks like a very handy mod but I don’t think I have the courage to disassemble my jointer and drill on it. I agree they need a TDC lock.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View ic3ss's profile


404 posts in 4113 days

#2 posted 05-22-2012 03:09 AM

The bearing housing can br replaced new for $10 and the cutter head for $65. If you make a mistake, they can be replaced pretty cheap.


-- "I am endeavoring, ma'am, to construct a mnemonic memory circuit using stone knives and bear skins."

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