stevenbunn Fri, 06/17/2016 - 07:34
Bending Jig for a Tracy Sack-back back bow
An ash bow steamed and bent around the bending jig for a Tracy Sack-back
I am currently working on several Tracy pattern Sack-back chairs. As I work, I have been snapping pictures for a book on the subject of making a Tracy Sack-back. My wife, who now does my photography, deserves my  thanks fo her willingness to put up with my demands to go out to the shop to take just "one more picture".
In the past, I have used a strap from a band-clamp to act as a backer to help prevent tear-out as I bend a steamed blank of ash around a jig. The flexible strap did a good job of reducing grain tear-out. However, I still had a higher failure rate than I would like, because in the process of bending the wood, the bending force on the outer face of the hot blank cause the grain to stretc. (The wood on the inside face against the jig is compressed.) The outer grain if overstretched can let go and tear. The band clamp strap I have been using does help suppport the grain as it is bent, but didn't counter act the stretching, which is the major cause of tear out. Somewhere, I wish I  could give credit here, I saw a picture of another chair-maker using a flexible metal band with fixed stop blocks. The stop blocks limit the stretch forces on the bow as it is bent. It looked like a good idea, so I tried it out. The results are pictured above. A successfully bent bow. I used an inexpensive strip of aluminium carpet molding as my flexible backer band. To save valuable time trying to fit a hot bow blank in the backer, I tied the dry bow to the metal band with twist ties. This allowed me to get the grain orientation right. No fiddling around with a piece of hot wood fresh ut of the steam box. Then I put the whole thing, bow and banding, in the steam box and steamed it as a unit. It worked beautifully.
In other news, I was once again juried into the Early American Life Magazine's 2016 Directory of Traditional Craftsmen. This is their list of the top two-hundred traditional craftmen which they publish yearly. I have been fortunate to be chosen for EAL's Directory a number of times over my career. It is a great honor.
Thanks for dropping by. STB