Jointer making convex cuts
I just haven't been flatten boards that are sufficiently long and I'm about to give up and reach for the hand tools, but my workbench project uses a lot of ironbark, so that's not very feasible.
Firstly, to make sure I have the terminology correct when I joint 2 boards, the middles touch and the ends are apart.
My jointer is an old wartime Delta that I had quite some issues setting up, but I've gotten it to a point it's satisfactory. To get the tables parallel, I shimmed up the outfeed table, but the infeed table has one corner closest to the cutterhead slightly low, but only ~0.1mm. It's the best I could do, as I can't shim the infeed table.
To set the blades, the blades in the cutterhead will stay in place without tightening screws, so I stuck the blades in there with an engineer's square over the outfeed table, and rotated the cutterhead so the square pushes the blade down to the correct height by itself. I did this with a piece of masking tape under the square, so that after I removed it, rotating the cutterhead over the square gave me the slightest bit of audible and tactile feedback that the blades were touching.
I lowered the infeed table to set the cut depth to 1mm.
When I cut, I pressure the infeed until enough has gone through that I start pressuring the outfeed. The feedback I get is that it takes a deep cut at the start, but after I transfer pressure to the outfeed and start trying to pull the wood through, I don't get much of a cut and towards the end it's like the rest of the board has lifted off the infeed table.
This tends to happen with boards over 1.5m long
Any idea what I'm doing wrong?