Sunday afternoon I'm going to be demonstrating how to be UNSQUARE with handtools. We spend a lot of time and effort trying to make everything square and true, sometimes it is a nice break to fool around with some curves.
Decided to post this under "Hand Planes" because the spoke shave is really the primary tool here for getting a decent edge on the ellipse. Really don't have a catch-all area for hand tool techniques except maybe the Play-by-Play.
As a quick demonstration I'm going to show how one could make an ellipse using only basic tools:
* Small rip or tenon saw
* couple of chisels
* straight edge
* #49 cabinet rasp
Add to that a few handplanes for clean up along with a bench hook and you are all set. But I'm also bringing along a turning saw for people to play with because it would go quicker if you could saw away most of the waste in an ellipse shape. Or any shape. Another bit I'm bringing for people to try their hand at is a template for a porringer tea table top.
Anyway, here are a few shots from a practice session this afternoon.
1) Lay out the ellipse. This is the usual method where you make a cross on the piece, locate the push pins at distances 1/2 the major radius axis from the center and a third temporary pin at the minor radius. Tie a string, remove the temporary pin and trace the ellipse. My knot wasn't quite tight enough so you see a bit of a spiral. I'll fix that later.
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2) If no turning saw or coping saw is handy, just use a small rip or crosscut to kerf in all the way around the ellipse. If you can remove a chunk or two now, go ahead.
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3) Get out the chisels and mallet and start removing the bulk of the waste. But be a little more careful than I was because I split a piece out where the mineral inclusion in the poplar made it brittle. Oh well, a lesson in stock selection!
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4) Now would be a good time to touch up the chisels because it is time to go back around and pare to the line. Works best if you work from the narrow ends out toward the wide end. This is the beginning of treating the ellipse as a shape with four quadrants and reading the grain to make the paring easier and minimize the chance the grain will run when you try to pare nearly parallel to the grain. Adding a clamp to the work might be a good idea too.
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5) And now it is spoke shave time! In a few places I had to resort to using a #49 cabinet rasp because this particular piece of poplar has a very brittle area near an edge as a mineral inclusion exits. Again, an object lesson in stock selection! Also, you may notice that my ellipse line is cleaner. I did a quick surface plane and then re-drew the line so it wasn't looking like a spiral any more!
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6) Keep working round and round the edge to the line. Each quadrant will want to work differently as the grain switches. By switching directions with the spoke shave you can always (or nearly so) work with the grain rising up into the blade and minimize the tearing and chatter. I used my thumbs down against the work as fences to help me keep the edge square (or squarish since we are being UNSQUARE today).
7) To smooth off the marks and layout lines, I set up a little cradle using a bench hook and two extra boards. The boards on the sides are clamped and keep the piece from spinning around.
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8) Pretty much done. Here you can see the little bit of tearout that happened on the other face due to the mineral inclusion. And perhaps a bit more work is needed at the apex because you can see some chatter marks. These could be worked out with the spoke shave set finer.
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All in all, the practice session went well. I'll probably make up a couple more models tonight, each stopping at a different stage so I can demo faster. I think this one took me about 45 minutes. I'd like the demo to last no more than 15 minutes so people can have time to "play" with the extra pieces I bring along.
I believe there is a video in the LV YouTube stream that demonstrates some of these things. I worked this stuff out from a few old books and fiddling about and asking some questions. Doubtful there is anything revolutionary here.