it provides a zero relief angle.
the jointer will still cut as long as the face is very small. because the relief angle is zero, there is more support behind the edge, so it will last a little longer before it needs sharpening. since the blades are now all cutting at exactly the same height you may actually get a better cut than you would have with the sharper blades before.
at least that's the theory....
I'm sure you will take your preconceptions to the grave.
In the meantime, I'll continue to get EXCELLENT results from my long lasting edges on my Powermatic jointer, YOUR NAY SAYING NOT WITHSTANDING.
Dave
Ahh, thanks for that, both of you. I was scratching my head trying to figure out what CW meant by 'clearance', but it makes total sense now. Friday afternoon brain cramp, I guess.
-John in NH
I've been fascinated by this thread, and some of the thought experiments about why this will or will not work (particularly the idea of why not just hone your plane blades the equivalent way). I note that the page from the PM manual that was posted on abpw refers to this technique as jointing the blades, not honing them. I found another source that describes the same process. Feirer's Cabinetmaking and Millwork, c 1970, follows a discussion of various alternative methods for grinding jointer knives, and how to install them, with this paragraph on page 258 (all typos mine):
********** After the jointer knives have been sharpened and reset, it is wise to joint the knives so they are exactly the same height. Cover all but about one-fourth the length of a large abrasive stone with wax paper. Place the stone on the rear table with the exposed section over the knives. Clamp a wooden stop block to the front table to help guide the stone. Lower the table until the stone barely touches the knives. [reference to illustration] Turn on the poser. When the cutterhead is revolving, move the stone slowly from one side to the other. A true cutting circle will result. Be sure to joint the entire length of the knives. The joint or land (sometimes called the heel) should not be wider than 1/32". After jointing, replace the fence and guard. *********I can't vouch for the technique based on personal experience, but I have found Feirer's book to be a pretty dependable reference. Combined with the page from PM, which is not a fly-by-night tool company either, I tend to think there may be merit to trying this.
The blade 'jointing' technique has probably fallen from favor by the proliferation of both homemade and commercial magnetic blade setting jigs that are pretty capable of getting blades accurately aligned to each other and the out-feed table - dependant, of course, on the user's skill and determination. Some of those suckers are really aggravating to align. And personal injury law suits have probably helped push it along. Some folks can break an anvil in a sandbox.
Greg G.
I'd buy that, except that Feirer's book discusses using a magnetic jig to align the blades when installed.
True. But while I've been happy with my success in aligning my knives and the resultant cut quality, this does make me wonder...
I suspect that had a lot to do with the change in the PM manual.
LOL!
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