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(Part 1 of 2)

Even with the expensive jigs on the market, setting jointer knives has never been something to look forward to. To make the job easier, I developed my own approach. If you fully understand the directions given below, you should be able to set all of your knives accurately in 20 minutes. This method is based on the traditional "plate glass" method but with a slight twist. With this method, you don't need a fancy store-bought knife setting jig. A bit of common sense and these common woodworking items are all you will need:

  1. 12" steel ruler
  2. Piece of hardwood - 10" long by 1" wide and about 3/16" thick
  3. Standard woodworking clamp or magnetic hold-down jig
  4. Piece of flat Plexiglass, Lexan, or Lucite - 6" x 10" x ½"

This process works on my 8" JET jointer because of the knife lifting springs on the cutterhead. If your jointer does not use lifter springs, this article will not work. It might be advisable to read this article completely before you begin to work on your machine.

A Strange First Step

The first step is to find the sharpest area of the blades and set your fence to make a cut over this area. Set the jointer to take the lightest cut possible. Next, turn on the jointer and run both long edges of the Lucite across blade as you would with a piece of lumber. Make as many passes as needed until the edge is true. There is a logical reason for this which will be explained later.

 

 

Finding the "Top Dead-Center"

Next, unplug the jointer. Now press the start button on the jointer a couple of times to be sure it is off. Now you need to find the maximum height of the knife during its rotation. This is often referred to as "top dead-center." This precise measurement can sometimes seem impossible to find, but don't worry about getting it absolutely perfect.

To find the top dead-center (or some place reasonably close), lower the outfeed table about 1/16". Then place a flat, steel ruler on the outfeed table and partially across the cutterhead. Rotate the cutterhead backward until the knife does not contact the ruler (photo 1). Using a pencil, make a mark on the jointer fence just above the front edge of the ruler. Now slowly rotate the cutterhead forward until the knife touches the ruler. You will notice that the ruler rides with the knife (moving towards the right).

Continue rotating the cutterhead forward. When the knife stops moving, place another mark on the jointer fence at the top edge of ruler. Now, remove the ruler and measure the distance between the two marks. Place another mark on the fence in the center of the two lines (photo 2).

Now, rotate the cutterhead backwards so that the knife edge is not touching the ruler. Place the edge of the ruler on the left most mark. Now, rotate the cutterhead until the ruler is moved to the centerline. This should be reasonably close to top dead-center.

Use light finger pressure to prevent the cutterhead from moving as you remove the ruler and place it against the fence on the infeed table of the jointer (photo 3). Slide the ruler up to the knife edge and use the magnetic hold-down jig to keep the ruler from moving (photo 4.) Note that the ruler should not be pinched between the fence and the magnetic jig or clamp. The ruler should be in front of the jig.

If you don't have the magnetic jig, clamp a block of scrap wood to the fence against the rulers edge (photo 5).

Now you should raise the outfeed table by 1/16" (back to its original position.)

Remove the ruler without disrupting the magnetic jig (or clamp). Remove the knives and sharpen them. Don't misplace the springs.

 

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Photo 1


Photo 2


Photo 3


Photo 4


Photo 5

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