john wrote:
I bought an old cast iron Craftsman 6 1/8" planer jointer (three blade)
last week. I bought new blades and installed them. I have them set to be
the same height as the bed. Now, at the blades, the back half of the bed
raises on an angle, the blades with it. The front stays level. I figured
why the back bed has to rise, to keep the cut level and not get
constantly deeper, using the front of the bed as the guide. Why is the
back bed flat if it raises on an angle? Why not raise and remain level?
How do I feed a board across the bed properly, to flatten the high part
of the wood? Is the flat surface of rear bed (angled during
cutting?)used for anything?

John,
One of us is very confused . . .
Unless your jointer is some peculiar child of questionable parentage,
both the infeed bed and the outfeed bed should be absolutely parallel
to each other in both planes - front to back and side to side. The
outfeed bed should be adjusted to exactly the height of the knives and
left in that position. The cutterhead should not move up or down, but
should remain in the same vertical position with the blades the same
height as the outfeed bed. Its only movement should be 'round and
'round. The infeed bed is raised and lowered to adjust the depth of
cut.

If your jointer is different from what I described, you're on your own.

DonkeyHody
"If your only tool is a hammer, you tend to see every problem as a
nail." - Abraham Maslow