I got another note from Drew Langsner this morning; here it is.
Here’s more on riving. This photo is of a gentleman who demonstrates riving shingles at Hida Folk Museum, near Takayama City in the Japan Alps. You can easily see that he’s been doing this for hundreds of years. He is riving chestnut.
It’s not shown in this photo but he will often rive a billet into thirds. Here’s the technique. He starts a split 1/3 of the way across the width. Shortly after the froe enters the billet he removes the froe. He then drives it half way in the remaining two-thirds of the billet. Immediately the froe is removed, replaced into the first opening, and driven down some. Then removed and replaced back into the second split. This continues until one of the side boards pops off. Then he finishes riving the other piece into halves. Very neat trick. I think the chestnut makes this somewhat easier than other woods because it is more bendy and therefore doesn’t pop apart as fast as a wood like red oak.
Also note his riving brake. I’ve been riving wood for shingles, chairs, fencing for 40 years now but had never seen anything like this. The brake not only holds the wood in place. It also puts pressure (tension) on the outer side of the curve and this causes the fibers along the curve to come apart as the split opens up.
One other trick. The master warms the wood over a small fire before riving. In winter this defrosts it. But I think that all year around it makes the wood a bit more bendy.
The froe is almost identical to the ones we use.
(Photo by Drew Langsner from the 2010 Country Workshops Japan Craft Tour)
Thanks, Drew. We’ll see more about the CW froe soon.