Troubleshooting an Out-of-Whack Jointer

      Woodworkers discuss what could make a jointer create taper on boards. January 10, 2006

The Powermatic 8" jointer seems to taper boards. Anybody have tricks to get this machine to do what it should? As you make a pass, the board contacts the outfeed for the first few inches, then lifts off the end of the outfeed. I have been messing around all morning with the 4 allen screws on the dovetail ways. Nothing seems good.

Forum Responses
(Cabinetmaking Forum)
From contributor R:
Typically, this is caused by your outfeed table being a few thousandths higher than the knives. Drop your outfeed table, which will cause snipe and slowly raise it up until the snipe disappears. Been working on machines for over 20 years.

From contributor F:
Yeah, what he said. You don't want to mess around with the gibs unless your tables are out of parallel. Sometimes, if you had it set up correctly to start and then the dulling of the knives changed how straight you can joint, moving the outfeed table will correct it.

From the original questioner:
Thanks for the input. I have dropped the outfeed and it seems better (on the left). Right side still not that great.

From contributor F:
You will need to reset those knives if they won't machine properly over the full width.

From contributor B:
The problem is your infeed and outfeed are not parallel. The wood touches the outfeed side after the cut and then loses contact and rises off the outfeed table as you feed. This means the tables are configured (barely) like a hill that the wood climbs up at infeed. I do not know if one or both of your tables is adjustable to correct this, but you can do it. You may also have a table out of plane left to right, which is equally adjustable. These are adjustments that should have been made at the factory, and may have been missed, or they might have been knocked off spec during shipping.

From contributor F:
About contributor B: He is jumping to conclusions about worst case scenarios that could be causing your jointer to act up.

About contributor R and I: We think the simple fix is where you should start. At first it appeared the knives were set below the outfeed table height and the fix was to lower the table a few thou.

Since that only worked for about half the knife width, I'll jump to the easiest to fix conclusion: The knives need to be completely reset. If you set the knives as close as humanly possible to the height of the outfeed table all the way across and then you still have trouble that cannot be cured by a slight adjustment of the outfeed table, look into contributor B's suggestions.

From the original questioner:
Thanks all. I think the answer lies somewhere between contributors F and B. I did get where contributor B was coming from, I just don't want to go there if I don't have to.

From contributor T:
My 8" General wouldn't cut right when new, no matter how carefully I adjusted it. I bought a 40" straight-edge and found that the tables were not parallel. General replaced the jointer, since the fix for that problem ain't pretty. It's easy to see if your tables are coplanar with a very accurate straight-edge.

From contributor B:
The worst case scenario would be warped tables. That is another possible source for this problem, but getting on plane is easier. As contributor T wrote, a good straightedge will find the truth. It's true that I probably assumed too much about the knife set, and even the outfeed height setting, as that is basic stuff. It all should be checked because any one of these problems throws off the whole balance of performance.

From contributor F:
All true! We once had an 8" Delta with a warped fence. When we talked to the company, they said to take it off, lay it on the concrete floor and stomp on it to straighten it.

From contributor T:
That should get it within a thou or two, eh?

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