setting jointer knives

[Tom Bussey]

I didn't want to steel James Baldwin's post so I thought I would post my own.

This comes from over 50 years of building tooling and special machines for industry. Please read everything carefully 1 and maybe 2 or times before responding. Please make sure you understand what I am saying before responding.

A datum is a surface, plane, line, or feature assumed to be prefect. It does not carry a tolerance but all dimensions are referenced from it. A good example is the footings on a house. If the footing are out of level then even if all 4 walls are perfectly parallel, they will not be level. And every floor after that will also be not level. If the footing are out of square the whole structure remains out of square.

Now a jointer, as far as I know has only 2 purposes. One is to flatten and the other is to edge. I do not know about you but I was taught the square off from the largest surface. And other pieces of equipment can be used besides the jointer to edge a board so in my way of thinking, the #1 purpose of a jointer is to flatten a board. If it was to edge then James wouldn't have spent the money for a 8 inch jointer.

Please stay with me here. When flattening a board on a jointer the wood is placed on the infeed table and after the cut is made partway on the board, the feeding force is then transferred from the infeed table to the out feed table. THEREFORE, the outfeed table is the datum surface. The infeed table has to be lower than the outfeed table and it does not need to be even on the same plane as the out feed table. Really think about it.

I would not try to shim the outfeed table in any way shape or form, The Datum surface is assumed to be prefect. and the infeed table doesn't really mater so leave it alone.

Now the cutter head needs to be parallel to the out feed table and not the other way around. Which is one of the reasons I do not have carbide cutter head. Due to metal movement and machining tolerances the cutter head may or may not be parallel to the out feed table. Another other reason is nothing is prefect, except for a datum and that is assumed, so all of the pockets on the cutter head will not be prefect. Wear in machine slides and cutting tool wear will make changes in pocket depth and size . An imperfect surface really shows up when milling metal with an inserted cutter. If I was to buy an inserted cutter head, then I would have to check and see if the cutting edges of the insert cutter were parallel with the out feed table.

If the cutting edges are not parallel with the outfeed table then I would have to shim the cutter head parallel with the outfeed table and not the other way around.

The out feed table is the datum which is assumed to be prefect, not the cutter head or the infeed table. The fence should be is set square to the outfeed table but the cut is determined by the cutter so if when you move the fence forward or backwards and your wood goes out of square it is because of the cutter head is not parallel with the out feet table.

And the fourth reason I will not switch to an inserted cutter head is I that have used my jointer for well one over forty years. (Long before inserted cutter heads) and I am comfortable with it. And since I am on a fixed income, $400- $500 is a lot of money.
I have been married to the same woman for 53 years and I see no need to switch to a different model now either. Did I mention than high speed cutters are sharper than carbide inserts.

My disclaimer is there is a difference between need and want and if you want an inserted cutter head and have the money, by all means go for it. To stay with steel knives is my choice, for me and me alone and not part of the reason for writing other than to say I would check and see if the cutter head is parallel to the outfeed table.

I have a lot more to say about datums so come back and check out what I am saying. I think I can save you some money down the line.

Also latter this afternoon I will get some pictures taken you you can see how to fix cutter problems.

[Tom Bussey]

I unplugged the jointer for the photographs even though it has a magnetic switch and can not restart until the on button is pushed.

The gauge I used is a direct reading gauge. Each line is one thousandths of an inch. I can turn the dial anytime I want to back to zero so I don't have to keep track of numbers as I progress. I start in the back because that is where I start, no other reason. I pick a blade and rotate the cutter head until I find top dead center. I use the belts the rotate the cutter head and I have very light clamping pressure on the knives. I do not have jacking screws so with a piece of wood( I like to use hard maple) I tap down on the knives and try to get all three knives with in about .005. It is not real important right now. Then I slide the one way gauge ( I think that is what it is called and it was purchased from Wood Craft.) And repeat the process. And it is backanf forth until all are the same height, I like to be with in .002 total indicator run out ( TIR)

Remember it is direct reading so what you see is what you get. Very gently tighten the screws because to much to fast will move the cutters. You can find out in a hurry if they move. And that is why magnets don't work. Even after it is indicated in, the twisting action of the screw can and will change the setting if you let it.

For me when all the cutters are the same height. (I want each cutter cutting the same amount off) and tightened down then I move the indicator to be completely on the out feed table and set zero. Now I slide the indicator it over a cutter, find top dead center.
and adjust the out feed table up or down until it reads zero. And you are good to go.

I have more to say on the subject but I am out of time.

[Tom Bussey]

Indicator at the back bringing in all three knives. second picture indicator at the front of the cutter head.

DSC03982.JPG DSC03984.JPG Next setting out feed table height to cutter head. DSC03981.JPG and lastly setting infeed table .015 ( 1/64th below ) cutter head. DSC03988.JPG
I will have more to say about the infeed setting later.

[Andrew Hughes]

I also use a dial indicator Tom. But with a button tip I find the highest point on the body of the head. Holding the indicator I roll the head backwards until the knife tip is on the small flat on the button tip.
On my jointer I lock the head in this position. I set all the knives out of the head equally within a thousands.
I set the outfeed height by lowering the outfeed below the infeed. Turn on machine make a cut on a fairly straight board until 4or 5 inch hangs over the outfeed.
There will be a gap raise outfeed until gap is gone. This something needs to done once sometimes twice to get it perfect.
I know there’s a few videos out there describing this method. I found a good video at 7:30 mark Patrick’s describes setting outfeed height. Have a look if you dare.https://m.youtube.com/watch?v=ob3V5SVrqAw&t=123s
Here my setup. Dig my Federal indicator smooth as silk.
Good Luck