Friday, August 22, 2014

Travisher is finished

After a couple detours, I'm done making a travisher. The lack of one was the last major impediment to moving on with my chair project, so I'm excited to start carving the seats.

There is not much info on the web about making travishers, so some pics and explanation may be helpful for folks who want to try rolling their own. There were two sources that were invaluable to me, however. The first was Peter Galbert's blog, of course. There is a ton of great information and many pictures of Pete's travishers, and I based mine pretty closely on his design.
The other source is Claire Minihan, who actually makes the travishers that Pete sells. She answered some emailed questions for me, and even better, sent me some photos of the construction process. Than you, Claire! Claire's and Pete's blogs are linked in the blog roll--check 'em out.

OK, so the first step was forging the blade. I had some odd-shaped scrap pieces of O-1 tool steel, so I hacksawed to shape and drilled a couple holes. Then, I heated the blade to red in my forge and hammered it around a 7" diameter piece of pipe that I scrounged from a local construction site. Then I "normalized" it (heating it past the magnetic point, about 1500° F, and then cooling it slowly), heat treated it, and tempered it. Here is the finished blade:

Above, you can see there is some pitting in the center of the blade, which is mostly due to my inexperience at forging. This is just cosmetic though; the edges cleaned up very nicely.

This photo shows the blade after grinding; I did not grind it until after it had been hardened. Look at Ms. Minihan's blog for an excellent description of how to do the grinding. She bevels the blades at 27°. I went a couple degrees higher than that, I think, but it's pretty close.

With the blade finished, I started on the body, using some nice quartersawn beech I recently acquired. There was was lots of drawing to come up with a shape I liked, then I made a cardboard template.

After that, I bandsawed the blank to shape, followed by lots of tedious planing, chiseling, rasping, and scraping. I spent a great deal of time making sure the bottom conformed closely to the curve of the blade, and I think this was time well-spent.

Then I forgot to take photos for a while. Oh well. In the pic above, two 8-32 threaded inserts have been installed to hold the blade, and the escapement (where the shavings go) has been marked out. After cutting along all the vertical lines with a backsaw, I broke out the waste with a chisel, then chiseled a smooth surface, finishing up with a mill-tooth file at the end. This was really easy--beech works like butter. I can see why it was the traditional wood for handplanes; it is dense and hard, but very easy to work with hand tools, and not prone to tearing or chipping.

Galbert travishers have a brass sole. I didn't have any brass on hand, so I decided to make a glued-on sole out of cocobolo. This presented some interesting challenges. For one, I needed a perfect fit between the cocobolo and beech to get a good glue joint. To do this, I started with an oversized piece of cocobolo. After getting the curve as close as I could by eye, I shot some spray adhesive onto 100-grit sandpaper, glued it to the bottom of the beech blank, and carefully molded the cocobolo until I had a perfect fit. Afterwards, the sandpaper just pulls off, and the adhesive is easily cleaned off with mineral spirits.

Then I glued it up:

Above, you can see the virtue of saving your leftover bandsaw cutoffs! There is also a stack of cardboard shims to help take pressure off the ends of the travisher.

Then I cleaned everything up and marked out the blank for sawing. This pic also gives a good view of the escapement. Sorry about the Chuck Taylors  :)

After bandsawing, there was more planing, rasping, and scraping until I got an even reveal on the sole. It needs to be about 1/64" below the cutting edge, and the inside needs to be beveled at around 45° to form a smooth transition to the escapement.

 The most important information I got from Ms. Minihan was regarding the shaping of the sole. She specified a 6° bevel, with a 1/32" flat directly in front of the blade. I got pretty close:

The only worrisome thing is that the cocobolo gets very thin at the bottom of the bevel. But it seems fine for now, and can always be replaced.

Finally, I cut the rather exuberant chamfers on all the long edges with a chisel, then scraped and sanded them. And that's it! Here are a couple more finished shots:

Oh yeah, it works:

The pic above shows that the tool cuts really well, but I badly need experience using it. So far, I'm able to hog off thick shavings, which is great, but I haven't yet acquired the touch for a fine finish. But with 4 chair seats to shape, I will get plenty of practice.

Monday, August 4, 2014

Making a Tapered Chair Reamer

One of the time-consuming things about making chairs for the first time is the never-ending list of specialty tools one needs. And if I don't want to go broke, I need to make, rather than buy, most of these. So, I am making incremental progress on that front. This week, I finished up a tapered reamer, used for boring the tapered sockets for the legs.

To the best of my knowledge, the design of this reamer was invented, or at least popularized, by Jenny Alexander; there's also a good article by Peter Galbert. One starts by making a blade from an old compass saw blade. These are harder to find than 'd imagined, but I eventually found a whole box of nice ones on Ebay for really cheap. I cut the blade down to 10", ground off the teeth on the 6" bench grinder, filed the edges straight, and then ground a 70° bevel on both edges. Below shows one of the saw blades next to my finished reamer blade.

The finished blade tapers from 1 3/16" to 5/16", over 10" (more on that later).

After that, I turned the shaft of the reamer on the lathe, drilled a hole for the handle, and cut a slot for the blade. The finished tool:

I tested the reamer out on some pine. It works as advertised!

OK, so here's a slight conundrum. Nearly every chairmaker who builds these call them "6° reamers." But if you do the math on the dimensions they use, the angles are actually in the 4°-5° range. I decided to be practical about this and use the dimensions that experienced chairmakers use, rather than worry about the angles. So, this one is a 5° reamer. I think it will work very nicely.

Next up: a travisher.