Thread: jointer knife problems

Possibly a silly question, but have you checked that the infeed and outfeed tables are coplanar? Or that the cutter head is running truly parallel to the table surface?

If they're not, then you cannot use the ruler method or a setting jig where both end-heights are the same and realistically expect a good set. You either need to be able to re-adjust everything square or, if that's not possible, need a jig where you can adjust the two ends slightly differently... ie. you need to fudge the knife settings to cater for the machines' faults.

For your sake I hope this isn't the problem but, given the symptoms, it's the first thing I'd check...

First up, check that the fence is actually square to the tables. Secondly, when you set the knife projection by measuring the travel distance that the knife carried a ruler, did you do this to both ends of the knife? Operator end closest to you and the fence end furthest away from you. An easy test is to find a 6" wide board that sits flat on the jointer table and measure the thickness of the board at both sides of the leading end. Mark the thicknesses on the board so you don't forget and then surface joint the board. Now measure the thicknesses on both sides of the leading end. With a bit of luck, the thickness will have reduced the same amount on each side and then you will just have to square up the fence and you will be good to go again.

Something else to check. I have a 6" long bed CT jointer, and noticed that as I move the fence in or out, it can become out of square. So you might set the fence square at the front of the table, but then move the fence back to joint a wider piece of timber and the fence would be slightly out of square to the table. I know that each time I move the fence, I need to re-check it for square. It's not ideal, but I live with it.

When surfacing the face of a board, as far as I know the fence only serves to keep the board tracking in a straight line.
In theory you could surface the board with no fence, but safety would be an issue.
The fence really comes into play when jointing the edge to an angle, usually 90deg.
Could a blade be lifting slightly as it is tightened ?
It may be just one blade that is lifting slightly on the fence side.

Regards
Keith

Set tables before setting the knives. Tables must be coplanar. Once done, blades are set to outfeed table not the cutter head. Fasten blade with the two outer screws only and only tight enough to hold the blade in position but loose enough to allow the blade to be pressed down or lifted. I still prefer the two bits of wood method rather than gauges. Place the two pieces of trued timber on the outfeed table, one at each end of the knife, projecting to just engage the cutting edge of the knife when the knife is top dead centre. Set the knife to just touch the underside of the timber. Hand rotate cutter head. Knife will move timber strips forward slightly. This timber movement should be equal, if so all is well. If not recheck knife is level at both ends to the outfeed table leading edge. Once happy, tighten all screws from centre out alternating each side of centre screw. Do not tighten the two outer screws at this stage. Check blade heights again before final tightening of the outer screws. By leaving these two screws as they were allows the others to be released right off if final blade adjustment is still required, without the blade going out of position. Final job, tighten down the two remaining outer screws on each blade.

Oh, the fence. Once the tables have been set up, the fence can be set square to the tables.

Hi guys so update
I checked cutter head and tables. After checking all I decided to get a dial indicator from a mate and found that the cutter head was raised at the back so I shined the cutter head and shimmed the out side of the outfeed table as that had dropped as well( freighted over from WA with everything else). Then tried the knife setting jig and run a board thru with the same results only not as bad only a very small gap on the inside corner

Thinking I will check the blades and see if I may have over tightened one but not sure how tight is enough

Can I also suggest that the part of the outfeed table closest to the blade is check for flatness across the table. I've got an old Wolfenden 12" jointer that has a slight depression near the operator side. In practice is presents no issues, but I know I can't use that spot to set the blade using the method suggested here.

Originally Posted by Trent14977

Hi guys so update
I checked cutter head and tables. After checking all I decided to get a dial indicator from a mate and found that the cutter head was raised at the back so I shined the cutter head and shimmed the out side of the outfeed table as that had dropped as well( freighted over from WA with everything else). Then tried the knife setting jig and run a board thru with the same results only not as bad only a very small gap on the inside corner

When you say you checked head and tables and then say that with an indicator they were out doesn't make a great deal of sense. They are either right or they are not. When you say the head was raised, in relation to what? Normally all adjustment would be in the tables, the head remains on its bearing beds.