Old-world meets new as a timber frame master goes high-tech.
Tedd Benson is a timber framing pioneer. As a modern builder practicing an ancient craft, Benson applied modern shop equipment and efficiencies to this old-world trade 30 years ago. It was not only the first such innovation in the United States in 75 years, it was the only innovation. And now the ultimate example is standing in one of Bensonwood Homes' huge New Hampshire shops: a 60-foot-long, computer-driven, $400,000 timber framing mill made in Germany by Hundegger. This thing is awesome to watch. It handles heavy timbers like they were matchsticks, and churns out fully milled posts and beams in the time it used to take to lay out a tenon.
Timber framing has traveled a long, grueling path to reach this point. After all, this is a 2,000-year-old craft practiced around the world. Throughout history, it has taken strong backs and lots of sweat to shape these frames with axes, adzes, chisels, mallets, draw knives, hand saws, and hand-cranked mortising machines. Most framers, including Benson, still use these tools today. An 800-year-old cathedral in Eastern Europe is held up with framing geometry that still befuddles experts, and a temple in Japan is torn down and rebuilt every 22 years so that each generation is exposed to its forefathers' craft.
In America, timber frames still support many of our old barns, churches, and colonial buildings. By 1900, however, the efficiencies afforded by wire nails, dimensional lumber, and balloon framing became standard in American architecture, and timber framing went into deep hibernation. In 1974, when Benson erected the first functional American timber frame in nearly 70 years, he applied modern tooling and shop advantages to the ancient craft and it woke up to a changed world.
New-Age Timber Mill
Not surprisingly, Benson's office is a timber frame structure, and it's here at a computer terminal that this high-tech timber milling process begins. Before a carpenter touches a saw or hoists a timber, designers plan and lay out the frame's elements--right down to the joinery--with Cadwork software. After completing this step, a "job captain"--a veteran timber framer--makes sure the CAD details are correct, feasible for the shop, and realistic in the field. Once approved, the program is translated from Cadwork to K-1--the timber frame machine's computer language.
Timber species and sizes are specified in the design stage. Timbers are rough-planed at the mill and delivered to the shop, then onto the Hundeg-ger's racks, where they're staged before milling.
This incredible device is a fully-automated joinery machine. It has a 750-mm--that's 29-inches--diameter blade, two 11/2-inch mortising bits, and four auger bits. Its universal mill drives a 50-pound, 5-inch-wide, 13-inch-diameter drum with 42 blades that cut tenons in seconds. Hoppers mounted beneath the machine pour snowstorms of sawdust into Dump-sters waiting a floor below. Each tool on the Hundegger follows a computer-program that manages each function--cutting timbers to length, slotting out mortises, and shaping near-perfect, rounded-over tenons on huge timbers' ends--all in a cloudburst of chips.
The Hundegger can mill a timber with relatively simple joinery quite easily and quickly. It can even do some compound work. I watched the Hundegger cut two mortises, two pockets, a tenon, and four peg holes on a 14-foot, 8x8 fir timber in 25 minutes. It would have taken one carpenter about 4 hours to accomplish the same thing.
The Hundegger looks like it belongs in a giant factory churning out oil-bathed auto parts, but it was inspired by the European timber frame industry to speed up roof- and floor-system work. After a job captain loads the Cadwork program into K-1, the operator orients the timbers' bad sides to where they'll be hidden in the finished building and coordinates that information with the Hundegger's program. The operator then grabs the timber with the machine's positioning wagon and manually aligns it for cutoff. After it cuts the rough-planed timber, the machine takes over and indexes every measurement it takes from the left side of its giant blade. The milling-operation measurements are referenced both mechanically and electronically, then simultaneously double-checked against the machine's computer program. This results in furniture-grade cuts.
Things get really exciting once the positioning wagon grabs a timber with its pneumatic knives. I'd swear the timber goes about 30 mph on the rollers as it is slides between operations, but Benson says it's really going about as fast as he can jog: 5 to 8 mph. The saw blade comes up, cuts off the timber, and disappears in about 2 seconds. The next stop is the universal mill, a precise and powerful cutterhead. It carries 34 teeth that are more accurately described as miniature planer blades. Eight perpendicular edge-cutting blades are positioned around the perimeter to get the cut precisely square. The mill's 11/2-inch tenon cutters are fluted drill bits that drill and cut on an X and Y axis. They allow the machine to make slots for mortises and pockets to accept timbers. Finally, auger bits drill holes for hardwood pegs that will ultimately hold the new frame together.
The Hundegger's cuts are surgically precise--so precise, in fact, that changing the saw blade can throw off all the other cuts if the blade kerf changes. The mortising operation, however, leaves a rough finish that requires a second surface planing. But the Hundegger is programmed to remove wood based on the timber's ultimate dimension. After it's milled, a belt drive off-loads the timber from the cutting racks and sets it on the planer tracks for its final machining.
Handwork by Craftsmen
Benson and his team have embraced technology and apply it where it makes the most sense. Technology guides repetitive cuts, the kind of work machines do best. That frees the company's craftsmen to focus on their specialties and work better, faster, and safer. The Hundeg-ger can't make complex, compound cuts like hip and valley rafters. It can't cut curves, it can't carve and embellish, and it can't work hand-hewn beams. These fine details are left to the Beam Team.
These workers use the same tools timber framers use across the country and around the world--huge circular saws, portable band saws, slicks, and chisels. You'll see a lot of Japanese-style blades on the chisels and slicks in Benson's shop. These tools are made with softer steel layered over harder steel. The hard-steel chisel backs are fluted, and the flutes' high sides are polished perfectly flat so the tool will be trustworthy and straight when used to pull up a curl. Timber framers care for their own hand tools. Framers use ball-peen hammers, grinding wheels, and honing stones to bend the soft metal's front side over the harder steel on the back. This forms a new edge that is honed scalpel-sharp and put back into use. Many average carpenters will get a new chisel rather than take time to sharpen a perfectly good old one. Things are different in Benson's shop.
Many of his frames are ornamental as well as structural. Their joinery is designed, cut, and assembled to furniture-grade tolerances--every joint fits perfectly, stock imperfections are removed or hidden, and smaller timbers are pocketed where they meet larger ones. Timber edges are often chamfered or rounded over with a chamfer plane or router. A chamfered edge is often terminated with a carving called a lamb's tongue.
For doing fine scrollwork on the end of an 8x10, a timber framer makes a wooden jig on the stationary band saw. He clamps the jig to the work and follows it with a router. To cut a scroll off a full beam thickness, he draws the profile on the timber and cuts it with a Mafell portable band saw. A carver takes over after all the mortises are cleaned, the compound joints laid out and cut, and scroll cuts adorn the timber ends. Hammer beams, prominent areas in a beam's mid-span, or king posts often receive intricate carvings, rosettes, gargoyles, or house names, details that surely make for a custom home.
In 30 years of leading the timber framing revival, Benson has managed to reincarnate a lost craft in America and master it as a designer, builder, and timber framer. Yet he's smart enough to "know what he doesn't know," so he surrounds himself with high-caliber people like designers, architects, engineers, and, of course, his Beam Team framers. He puts the best tools to work in the most efficient surroundings he can, and has managed to automate and streamline what has historically been a slow, muscle-bound process. In the end, Benson has improved quality, increased productivity, and enhanced the lives of his long-time framers without compromising the craft.
Mark Clement is senior editor of Hanley-Wood's Tools of the Trade.
