Thread: Jointer making convex cuts

Originally Posted by havabeer69

get this man a vaccuum.

Just out of curiosity, how are you checking the flatness? engineers square?

I may not be correct but if you're adding shims to the top of the table there must be something quite skew-iff with your jointer

also what are the bearings like?

I do need to clean up my shop haha! but I can't work out the dust extractor and keep putting it off

yea I'm using engineers square. but the boards are more than just a little bit cupped. after a few passes they rock on the jointer beds.

the jointer tables are very badly off, and with gib screws untightened, it moves in every dimension, and it's very hard to shim because when I tighten the gib screws it moves back. it's hard to explain, but it's a very old machine that's no doubt had a ton of wear. I'll persist with it, though because it has a smooth and reliable (albeit slow 3500rpm) 2HP induction motor.

the cutterhead is very smooth and quiet, so I don't have any issues with the bearings.

I don't think shims on the top surface of the tables is the answer. If you can't get the tables sorted then maybe a new machine is in order. Not necessarily brand new, but another one that works (all my machines are second hand that I've fixed up a bit). The whole point of the jointer is to get one face flat and an adjacent straight, square edge. If your current machine can't do it, then I'd be getting another.

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A jointer that is not coplanar is an absolute PITA. An easy way to test is with a long straight edge that is at least the length of the machine. Drop the infeed table below the outfeed, set the straight edge down the centre of the tables and weight the outfeed side. The straight edge should now be riding flat on the outfeed and not touching the infeed at all. Place two small pieces of paper under the straight edge, one close to the cutter and one at the tail of the infeed, raise the infeed until one or the other of the pieces of paper just pinch between the infeed table and the straight edge. If both pieces pinch at the same time your tables are spot on. If not, you need to adjust the tables until they do.

Originally Posted by Fergiz01

I don't think shims on the top surface of the tables is the answer. If you can't get the tables sorted then maybe a new machine is in order. Not necessarily brand new, but another one that works (all my machines are second hand that I've fixed up a bit). The whole point of the jointer is to get one face flat and an adjacent straight, square edge. If your current machine can't do it, then I'd be getting another

yea, it's like the wood gods just want to let me know that it's not happening

You don’t need a new machine. Even after 60 years of continuous use, the tables on our old Pioneer jointer were perfectly aligned. The dovetail ways don’t wear at all because the infeed table only moves half an inch, maximum. Keep working on tuning it, work methodically, make notes if you have to, for each step. start by getting the outfeed table rock solid and perfectly in line with the cutterhead, without knives in it. Then move onto the infeed table, adjust the gibs on the dovetails so they have only oil clearance then you can check for parallel along the length of the two tables, then use winding sticks to check for twist between the two. Then put your knives in and set them to the out feed table. I’ve adjusted plenty of jointers at places I’ve worked, they’re not hard to get running well.

Thanks for the tips folks. I've been having the same problem of the jointer cutting the board convex along its length, and I've suspected my technique first. The board ends up cut skinny at the front, and not touching at the back. Based on what I'm reading here, I'm needing to push down earlier and harder on the outfeed table.

So, I haven't been able to resolve the slight cup across the width, but by lowering the outfeed table slightly I've managed to get rid of the convex bow. Boards are flat enough that I can put it through my thicknesser and then dress the other side. Not quite the precision instrument I was hoping for but I'll persist with it