Jointer cutting a taper or a dip

What you see

1. The jointed edge or face comes out hollow or off straight along its length, often worse at one end, instead of flat.

   4 sources agree , sources [1, 2, 3, 4]

Likely causes

Most-agreed first: the more makers name a cause, the higher it sits.

1. The outfeed table is not level with the knives at the top of their arc: a little high or a little low.

   4 sources agree , sources [1, 2, 3, 4]

2. The infeed and outfeed tables are out of parallel with each other.

   Two sources: Grizzly Industrial and RIKON Power Tools , sources [1, 2]

How to tell which

1. Hollow at the trailing (back) end of the board: the knives are set higher than the outfeed table.

   Two sources: RIKON Power Tools and JET (JPW Industries) , sources [2, 3]

2. Hollow at the leading (front) end of the board: the outfeed table is higher than the knives.

   Two sources: RIKON Power Tools and JET (JPW Industries) , sources [2, 3]

3. Hollow along the length, or in the middle: the tables are out of parallel.

   Two sources: Grizzly Industrial and RIKON Power Tools , sources [1, 2]

What to change

Change one thing at a time, so you know which change fixed it.

1. Set the outfeed table level with the knives at top dead centre, as your jointer’s manual describes.

   4 sources agree , sources [1, 2, 3, 4]

2. Bring the tables back into parallel.

   Two sources: Grizzly Industrial and RIKON Power Tools , sources [1, 2]