Plane cutting edge shape

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Forum topic by BJODay posted 03-19-2014 02:49 AM 1186 views 0 times favorited 4 replies Add to Favorites Watch
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526 posts in 1971 days

03-19-2014 02:49 AM

Topic tags/keywords: plane

Hi all,

I was following links about Stanley replacement parts. I came across a diagram showing the recommended shape of the blades cutting edge.

The diagram showed a smoothing plane as having a straight edge with a slight radius at the corners. This makes sense to me. Round the corners slightly to reduce putting a line in the work.

The Jack plane edge was curved. An 1/8” from center to edge. This seems a bit much to me. This sounds like a scrub planes edge. Am I mistaken? Should a Jack plane, (Stanley #5), be curved that much?

The third image shows a slight curve for a jointer plane. Would this also be correct?

Thanks for any information. I enjoy learning something everyday.


4 replies so far

View DocBailey's profile


584 posts in 2388 days

#1 posted 03-19-2014 03:04 AM

Those are correct indeed
In a three plane setup, the 3 planes correspond to coarse, medium and fine (jack, jointer & smoother, respectively)
Consider the rough dimensioning of a piece of wood. One would begin by flattening a face.
In this scenario, the jack is not unlike a scrub. One would diagonally traverse the cupped or twisted face and hog off the high spots. Then follow up with the jointer, then the smoother.
The Jointer, when cambered as shown, makes edge jointing a lot easier too.

View jmos's profile


840 posts in 2398 days

#2 posted 03-19-2014 12:07 PM

While I agree with Doc’s assessment of course medium fine, there are different thoughts on blade shape. I agree on a cambered Jack, but I wouldn’t camber it that much, seems excessive. It does seems more like a scrub plane. That being said, I usually use a powered jointer and planer, so they are doing my rough work. If I was starting with unfinished lumber I might go to that much camber.

I agree with the jointer, a slight camber is a good thing, especially for edges. This allows you to take a heavier shaving on one side or the other, depending on how you position the plane on the work. With a straight blade, how do you fix an edge that is not square, short of being able to hold the plane exactly square to the edge?

I like to put a very slight camber on my smoother (~1/64th), rather than just rounding the edges. I’ve had better luck eliminating the plane tracks that way; but as shown it should work.

-- John

View JayT's profile


5679 posts in 2239 days

#3 posted 03-19-2014 12:58 PM

Oh boy, you’ll get a lot of different opinions on this one.

The above setup is pretty common. Personally, however, I do not camber my primary jointers—they are straight with eased corners. I also have a cambered one, but it hardly ever gets used for jointing.

My fore plane and one jack plane are cambered at least as much as what is shown for the jack. These are the ones I use for scrubbing off rough lumber, initial flattening and dimensioning. That dramatic camber allows you to remove a lot of material quickly. The surface will get evened out with the jointer and smoother.

Most of my smoothers are straight with eased corners. The diagram above show a really drastic radius that isn’t necessary. Five strokes for each corner on the final shapening stone putting pressure on just the corner is enough. If you put a straight edge on my smoothers, the corner relief is barely visible—a few thousandths of an inch. Just enough to not leave tracks.

-- In matters of style, swim with the current; in matters of principle, stand like a rock. Thomas Jefferson

View Roger's profile


20929 posts in 2832 days

#4 posted 03-21-2014 11:58 PM

Thnx for those drawings. I don’t know anything about planes, except for the fact that I don’t like to fly. OH, wait, that’s another kind of plane. Anyhoo, thnx.

-- Roger from KY. Work/Play/Travel Safe. Keep your dust collector fed.

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