Jointer accuracy question/poll

[Allan Johanson]

Hi gang,

I'm trying to set up my new jointer and am wondering how accurate it should be with regards to knife height (esp side-to-side), table parallelism, etc.

My test is as follows:

1) Take a board about 6" by 24" and face joint it to get a flat surface.
2) Run it through the thickness planer to get a consistently thick board
3) Double check the thickness at the four corners with a dial calliper
4) Set your jointer to a light pass, maybe 1/32"
5) Run the board through the jointer, jointing the same face 4 times in a row
6) Measure all 4 corners with a dial calliper again

What do you see? The same thickness at all 4 corners? Or are you out side-to-side and/or front to back? How much are you out? I suppose if your machine is perfectly set up and your technique is perfect, you'll get the same numbers at all 4 corners.

I realize this is wood, and not a high-precision machine shop making engine parts, but how far off would you be comfortable with?

Thanks!

Allan

[Todd Burch]

Hi Allan. I would never do this test. If I needed a thinner board, I would keep running it through the planer!! LOL!!

I guess the proper test would be to make sure that no matter how many times you ran it through the jointer, was it still flat on the one side? If the answer is yes, who cares about how much it will screw up a perfectly good board?

[Allan Johanson]

Thanks Todd. :p

For 99% of the time you'd use a jointer, I suppose you'd get the face flat, then one edge and then go to your planer and tablesaw to deal with the other face and edge. Mulitple passes aren't an issue so my error magnification test would be unfair.

Doing a tapered leg on the jointer is the only case where I could see multiple passes occuring where the error could add up.

Unless anyone else can think of other situations.

Maybe I should stop worrying and start making sawdust? :D

Allan