Planer problem

[Dick Van Ness]

I have a Delta 22-540 12" planer. I'm trying to plane 11-1/2" cherry boards. I wasn't able to joint them because of my 6" jointer, so I put them through the planer directly, because they are high quality figured boards from Irion Lumber and are very flat. I figured if I took 'baby steps' in planing them, I would knock off the high spots and gradually get the top reasonably flat and then flip them and plane conventionally. Everything went very well, the boards are beautiful, but they have a slight crown across the width. I'm still 1/4" away from finished thickness, so I can probably experiment a little bit. The gap is probably 1/32" at each edge. Does anyone think I have to take the knives out and check them, or sharpen them, or replace them, or is something else wrong? I tested the planer on another perfectly flat and planed board, and it did the same thing. I've never planed a board so close to the maximum on the planer. Does anyone have any suggestions? I'd appreciate any help I can get.
Thanks.
Dick

[glenn bradley]

The feed rollers press the crown out of the material prior to reaching the cutterhead and then the crown returns once the material is past rollers. This is why reports of success at flattening a surface with a planer using light cuts have to be taken with a large grain of salt. So many variables come into play that will effect your success, or lack thereof, in doing this . I'm sure plenty of people will chime in with how they do this all the time but, the physical process and cutting geometry of the machine do not support this. Soft feed rollers might contour to an irregular feed path but, again, success may be elusive or happen just enough to keep you at it (like when I golf) ;). A planer sled would help you produce predictable repeatable results.

[Judson Green]

Sounds like you could make quick work of the slight convex with a good old hand plane. After you've gotten rid of the convex with a hand plane, carry on as you were dimensioning your lumber.

Just my 2¢

[Andrew Pitonyak]

Have you considered using a sled and then using shims so that the planer does not push the board flat? This is how I do it and I use hot melt glue for the shims. Well, that is what I used last time anyway.

[Dave Cullen]

If the planer is making a perfectly flat board convex then something is wrong with the planer. Definitely check the knife alignment.

[Bob Lang]

The feed rollers will squeeze the crown flat as the board passes through the machine. However, your knives may have worn in the middle if you don't normally feed stuff near the edges, making that effect worse. If that were the case it would be easy to check by taking the cover off and holding a straightedge against a knife, and the knives would be pretty dull. Even with brand new, super-sharp perfectly straight knives, you need a flat surface to get over the feed roller effect.

Bob Lang

[Steve Kohn]

A lot of guys on this forum have 12 inch jointers. What is your location and maybe someone would offer to run your wood over their jointer to flatten it for you. If you're in the Chicago area send me a PM.

[Josh Doran]

I had the same issue. I discovered the planer bed was humped along the middle. Is your bed flat?

[Lee Schierer]

I have a Delta 22-560 and I don't get a crown on my wide boards. Check to insure your lower table is flat. While the cutter head is raised wax the table with Johnson paste wax so the boards will slide more easily. Then remove the cutter head cover and remove one of the knives. Check to see is the knife is straight. Most likely the knife is dull particularly in the center, because most folks naturally run the boards down the center of the planer. Fresh blades are fairly cheap and easy to install. Your knives may be reversible. Just make sure you get the new knives in straight and even in height. When cutting wide boards, it is important to take very light cuts to keep the cutter head speed up. I take no more than 1/4 turn of the height adjustment handle at a time, which removes about 1/64.

[J.R. Rutter]

I'm not saying that it isn't a planer issue, but just keep in mind that most lumber has a different MC on the surface vs. the middle of the thickness. As you remove material, you release some tension. If the center is drier than the outside, the growth rings will try to straighten out. Likewise if the center is wetter, the growth rings will become more concave. And if one face ends up drier, then it will cup in that direction. Sometimes things will even out again as the wood reaches new equilibrium, sometimes not...