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
It sounds like your a little confused about the outfeed table. Both tables should be parallel (in plane) with each other. I think that you are talking about the dovetailed ways which are on an angle which is what the table raises and lowers in, but always in the same plane. At the same time it raises/lowers the table it moves the table towards/away from the cutterhead to allow for the radius in the cutterhead which keeps clearance consistent as you adjust height.
"the back half of the bed raises on an angle, the blades with it" Now that has me a little confused. The cutterhead should not move at all. It is the only part that is fixed to the base of machine and does not move. If it does it will be the first time I have come across it. If this is the case it would be good if you could post a photo somewhere so we can see how it is set up.If you have any info on brand/model number of machine someone may know the machine and able to help a little more.
The only time the outfeed table should need adjusting is after installing knives. As a general rule the outfeed table should be set to level with knifes or sometimes some set it anything up to .015" higher. Most jointers have some sort of locking mechanism on the outfeed table gibs (usually centre bolt) to lock table once set. The infeed table height is the one that controls cutting depth.
AS for flattening technique it depends if you are talking about a bow or a twist.
If its a bow ( looking along edge of board it curves up or down) It is usual to surface with bow facing up (high part in centre). Feed through in direction of grain. Do not place pressure in centre of board to force it flat, just a gentle touch to guide it through.
If its a twist/wind (both ends of board out of parallel with each other) Place pressure on the corner that has contact with table. Feed through keeping pressure on this side after passing to outfeed table. All the time trying not to rock the board. On infeed table move feed pressure to opposite corner at rear of board (also in contact with table).
It may take a number of passes depending on how bad the bow/twist is before you straighten it.
In summary ... don't place any pressure on board where it has no contact with table.Let the jointer do its job (straightening) and you do yours (feeding).
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