PM 100 planer knives: 12" instead of 12 1/4" ?

[Allan Speers]

I'm trying to get my 1980's PM 100 running. I was going to get a Shelix head, but I really can't afford it right now, so I want to get carbide-tipped straight blades instead. (This planer gives such a good finish, the only real advantage of a Shelix head is low noise.)

Infinity tools has one heckuva' deal right now: $129 for a set of three ! Except these are 12" long. While the 1960's (Green era) manual specs 12", The 1980's (Gold era) manual calls for 12 1/4" blades.

I don't know if Powermatic actually changed the head. most likely they just realized that the extra 1/4" allows some wiggle room, especially if you get a nick as you can then move that blade sideways a bit to offset it.

American National has the correct 12 1/4" blades, but they want $242. That difference in price would by a lot of coffee & donuts.
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So, would I be foolish to get the 12" blades? What would you do, if money was really tight?

[Mike williams54]

Take some measurements, as long as the knives are the same or very close to the same height, and the exact same thickness, I doubt 1/8" overhang on each end will cause any problems. Just look around your cutter head to make sure though.

[Steve Peterson]

Planer knives don't seem overly complicated. Look at the existing ones to see if there are any holes. If there are holes, then you need to make sure the new ones have properly spaced holes. Otherwise, they are just hunks of metal that need to be bolted in place. Slightly narrower might allow a bit more wiggle room if you hit a nail and need to slide a blade sideways.

Steve

[Bruce Wrenn]

Global Tooling has a set of 12 1/4 for $156.51. They list both lengths for Powermatic.

[Allan Speers]

Global Tooling has a set of 12 1/4 for $156.51. They list both lengths for Powermatic.


Sweet ! - thanks.

[Dan Hahr]

Every now and then a wide board gets right up against the guide rail. If the blades didn't get all the way over to the sides, you could have a high spot along the edges.

Dan

[David Kumm]

You should be able to shift one blade 1/4" and one the opposite and not muck up the balance. Dave

[Curt Harms]

You should be able to shift one blade 1/4" and one the opposite and not muck up the balance. Dave


Exactly. When I bought my Jet "12" jointer/planer I bought an extra set of 12" knives. I didn't discover until some months later when it was time to sharpen the orignal knives that the cutterhead is really 12 1/4". Offset one knife and I can't tell the difference.

[Mark Wooden]

12" knives are just fine, offset them as David suggests if needed. I have 12", 12-1/8" & 12-1/4" knives for mine, no difference with any really.