Surface planer designs that hold double edged knives

[Stephen Tashiro]

How do the knife holding assemblies on surface planers avoid dulling the unused edge while the other edge is being used?

The only surface planer that I have is an old Sears 12 inch Craftsman model 351.23373. Delta 22-547 knives that are easily available at Lowes are double edged and match those in the planer except that the old ones are single edged. The knife holding assembly on my planer has two screws with flat heads and the back edge of the blade rests against them. The screws are used to adjust the depth and angle of the knife before a plate is tightened against the knife to hold it permanently. I'm wondering if the unused edge of the blade would be damaged by these screw heads (which I don't mind) or whether the blade would shift because only a thin part of it is resting on the screw head (which I would mind).

[Jamie Buxton]

Generally, the knives have holes through them. There are studs in the cutter head which go through the holes, and a keeper bar which prevents the knife from coming off the studs. So there's nothing touching the knive edge which is not in use.

[Stephen Tashiro]

Yes, I've seen planer knives with holes in them and I see that modern planers advertise that their knives are easy to change because of systems of pins that locate them precisely. But the Delta double edged blades that I am tempted to use don't have any holes in them. So some Delta planers must have a different scheme.

What I am agonizing about is whether the double edged blades would stay in place in my planer.

[Stephen Tashiro]

I found a post (http://www.sawmillcreek.org/showthread.php?t=78430) where Eddie Darby gives a link to the Delta 22-540 planer that uses the double edged knives that would fit my planer. That manual shows the same general type of knife holding assembly as on my planer except there are no depth adjusting screws that contact the unused edge of the knife. Instead of screws, the planer comes with a jig and the user must set the knives without the aid of adjusting screws. So my current guess is that the double edged knives would work in my planer and that the bar that presses against the knife will hold a double edged blade. The manual also says to tighten the seven screws that hold the bar starting with the end-most screws. This surprises me. I'd think that starting with the middle screw and working toward each end would best relieve stress. Perhaps the idea is to build-up stress.

The internet is certainly a wonderful source of information. In the old days, you had to take the personal approach and ask the local expert in town. in my home town , on most mechanical matters, this was "Mr. Mead". Of course , one cannot expect a complete or certain answer either from the internet or Mr. Mead, so I'll just have to try this idea out. I'm inclined to put small disks of cardboard or some soft material over the head of the adjusting screws to try to preserve the unused edge of the knife.