Jointer and planer knives setting jig.

[Joe Spackle]

I am not a tech writer.

Uncomplicated version.

TDC is always going to be about the cutter head.

Not the tables. You need to find it only once.

Then scribe a mark on the bearing housing.

Corresponding marks on the head.

It should be one of the first things you do on intial setup

of a brand new Jointer. My father marked this one in 1964

when I was 6 years old. Never changes.

Per

so did he find TDC a DI or the glass or with a stick or ???????

Dad had to find it some way

Just curious........

[Dennis Lopeman]

I'm googling this right now! upon first couple links and reads, it doesn't look easy!

[Adam Potack]

I did something similar to the glass & magnets. I sank a magnet flush with a piece of 3/4 mdf, covered it with blue tape. Wish I thought of putting a magnet on the back end but holding by hand worked. This worked well It din't take too long to set my jointer knives, they were straight & all at the same height.

I cheated on TDC. I tweaked the outfeed table after setting the knives.

[Dan Karachio]

I agree, for jointer knives it is all about finding Top Dead Center, not the jig. In addition, to marking TDC, you need a way to hold it there. I found that once I can lock the head at TDC for each blade, it is fairly simple and almost fool proof to set the blade height whether using a magnetic jig or straight edge. If you don't lock it, it can and will move, especially with the magnetic jigs, and as a result your height will be off (probably too high). Some times you can wedge in shims to lock it at TDC or put clamps on the motor belt. Whatever works, try it. For my jointer, taking off the fence made this much easier to do.

[George Brown]

I use a jig that rests on the knife holding cylinder directly, so TDC is not an issue. I turn the adjusting screws until the blade just touches the jig.

[Kyle Iwamoto]

I use a cheapo device called teh Jointer Pal. Check Amazon. There are various priced versions. I have the cheapest version. There are some 1 & 2 star reviews, but both of those refer to a non locking cutterhead. Now I personally don't understand how that relates to the jig, but that's someone else's opinion. It's not a hi tech super accurate tool, but neither is the price. You can get better but you pay for what you get. For less than 40 bucks I think it's a great deal. Similar to the magnet/glass idea. But since it's on plastic sticks, you can easily tighten the blades with the jig in place. I got mine a LONG time ago for 20 bucks.

Just my 2 cents.

[Dennis Lopeman]

I found TDC... man... it's simply the highest point on the the cutter head!! Which is obviously the same around the whole cutter head b/c it's round... darn near perfectly (right!)... why didn't someone say that!!??! LOL

Joking - I probably missed someone stating that.

Anyway.. my jig board magnets did the trick. I tested and I got a nearly smooth surface... way better than I had using another trick I tried last night... Still a slight ripple.

Now I'm going to build the Swenson Jig using glass. I have rare earth magnets I took out of some old PC Hard drives. I have glass.

Tomorrow - re-allign the blades and obtain perfection!!!

[Paul Hingco]

I don't really have to set the height for my planer knives. I only have to match the holes of the knives with the tabs on the planer head.

For the jointer, the easiest method I've found is using a Jointer Pal in conjunction with a Dial Indicator.

http://www.youtube.com/watch?v=2UPXuGm7-2w


Others swear by the stick method. For kicks I sometimes use it to triple check my knives are set properly.

[Chris Parks]

I found TDC... man... it's simply the highest point on the the cutter head!! Which is obviously the same around the whole cutter head b/c it's round... darn near perfectly (right!)... why didn't someone say that!!??! LOL

Joking - I probably missed someone stating that.

No, it is the highest point of the blades, a big difference.

[Charles Cannon]

No, it is the highest point of the blades, a big difference.

Shouldn't the Highest point of the head also be the highest arc of the knives?
Cannon

[Chris Parks]

I presume the head is truly circular and has no one point higher than the other, in that case the blade has to be plotted to TDC. I don't know why manufacturers don't reference TDC as it would be easy enough to do.

[Myk Rian]

Shouldn't the Highest point of the head also be the highest arc of the knives?
Cannon

Yes. Once you have TDC of the head, TDC of the blades is the same.

[Chris Parks]

TDC as a reference in planers or jointers is actually as many points as there are blades. In other words you have to know TDC at each blade to set the height to the table. of course if you don't set to the table you don't need TDC just a measurement off the head that is exactly the same for each blade. A truly circular drum WILL NOT HAVE A TDC.

[Dennis Lopeman]

I'm in the camp that the head (being a near perfect circle, round, etc) has it's TDC at its "highest point"... Basic geometry, right?

Draw a perfect circle. Draw a perfect line and butt it up against the circle. Mathematically, it will only touch in ONE point on the circle. To the naked eye, of course, that looks much wider.

Now, with that in mind, you know you want the blades to stick out to the same height all the way around. I think that if you pick one exact place at each entry point of the blade, or the tip of the blade, or anything... just doing the same for each blade will make them all stick out the same distance. But we want to pick the TDC because we don't want the tip of the blade to stick out higher the the outfeed table!!

So I found a video: http://lumberjocks.com/GarageWoodworks/blog/14488

Seeing it was helpful. Using this method (I have a digital dial which actually makes it a little harder!) he shows finds the TDC, which obviously is also the very middle of the arbor, head and all.

So I feel confident that TDC is also the first point a straight edge would touch on the head if it were resting on the outfeed, lowering the outfeed until the straightedge touches the head. right were it touches is the TDC. And therefore, in quotes, that is the "highest" point on the head. (in quotes because that is in reference to the OUTFEED table.)

More geometry will also show you if you were to draw a line coming down from that TDC and straight edge, pass the line right through the very center of the circle (the arbor's center), then THAT line would be exactly 90 degrees perpendicular to the straight edge.

So I would also then deduce that I could find TDC with a sqaure, if I were able to hang it over the outfeed table and pass the other leg over the exposed arbor (on my jointer (Delta DJ15) I can actually see the arbor end) - I would just need something on my outfeed table to make it stick out so the square could align along the arbor - perhaps my glass Swenson Jig!!! - funny that the piece of glass that I have is much wider than my 6" table. I'll try it tonight and see how close last night's TDC finding is.

[Jim Andrew]

About 35 years ago in an earlier life, I did a couple years as a woodworking teacher. The school had a 8" powermatic jointer, and they had the powermatic knife adjustment tool. It was a gadget that sat on the table, and you just used an allen wrench to adjust the knife up or down and the gadget had a gauge which you used to set the blades. Much easier than anything else I've seen. Could replace the blades in 5 minutes before school started.