For those not aware
Denis Ch�nard, Orl�ans, Ont.
>Preiss (the author of the scathing letter) used to be an editor of Fine Woodworking 20 or so years ago. Just so that you know... I think he was "over the top" in his criticism of Charlesworth, but like anything there's no black or white, only shades of gray...
WARNING: enlightened rank amateur here...
Last week I would have called myself a pure rank amateur, but for the last four days I've been taking a Craftsmanship class at Rosewood Studio. The owner, Ted Brown, was a student of James Krenov at CR, so I would call his credentials pretty solid...
Preiss has a major issue regarding the use of cambered irons. I used to think that way. I thought that easing off the corners was sufficient with a flat blade. The teaching I received this week has had me re-thinking that point of view.
This week, as part of the curricullum (sp?) we had to make the "perfect board". One perfectly flat face (no plane tracks or any other blemish), with an edge at a perfect 90 degree angle to the face, then the edge both at 90 degree to the face and the edge. ABSOLUTELY no room for error. Half a thou off was "fail".
Before getting on that exercise we were taught the fine points of grinding and honing a slight camber on the plane blade. We were told (and demonstrated) the reasons as to why we should use a camber, and how to use it to our advantage while smoothing the face and correcting an angle that's off 90 degree on the edge. I won't get into the details here, let's just say that the approach makes sense.
I was kind of the "black sheep" of the group's students, I used flat blades and sandpaper (on granite) instead of grinders and stones. Still I tried to put some camber on my LV LA jack blade (which I love dearly). Getting a camber on a low angle bevel up plane blade is a lot more work than on a bevel down blade, so I ended up with a "thinnest shaving" much wider that what can be done with a BD blade. It ended up being a good thing, Ted actually told me that he's never seen a surface that good from someone who uses sandpaper for honing (and a bevel-up plane, for that matter). My conclusion: less camber (but more than zero) is better on the board's face. A very shallow camber does a better job, IMHO.
When it came to trueing the edge, more camber had its goods and bads. While having a camber makes it relatively easy to correct the edge's angle (run the plane off on the high side of the edge, with a final pass in the middle when the edge is at 90 degree), with the cambers used with our planes the middle of the board's edge would be a couple thou or so shy of flat. Fine if you are trueing the edge of a tabletop, not so good for edging boards for glueing (especially with non gap-filling glues like PVA) IMHO. The end was trimmed with a block plane, flat iron, that made for more work.
After all that work, they had us rip that board in two (on the principle that if you have a narrow jointer you will need to split the board up so that you be able to joint each part), but it had to be done in the least visible way, and then glued up back together. That meant cutting the board along a grain line as straight as possible, whick was inevitably not in line with the board's length. Jointing the edges individually with cambered blades to then glue the two parts back together was a major PITA, somehow I couldn't get the whole edge right. Out of frustration I went to the Rosewood store, purchased a LV BU jointer, re-ground the blade to a flat 34 degree angle, clamped the two pieces together and jointed the edge. 3-4 passes and that was it.
Bottom line, the cambered iron approach has benefits, but is not a panacea. In certain situations a flat iron is best.
Regards, from an "enlightened" rank amateur,
DC
