Wood Bending Instructional DVD
Review by Mark Gezella – July 2007
Well, I missed the last meeting, and had no chance to browse any books this past month. So, what's a librarian do when he's in a bind? Why, talk up more Adams DVDs of course! I had a chance to view several of Marcs videos over the last holiday break, taking copious notes and committing as much as I possibly could to memory for occasions such as this (my contingency plan, if you will). I've already talked about the Adams Furniture series and Marquetry DVD. This time around I thought I'd describe his video on bending wood.
Why Bend Wood? Marc asks this rhetorical question as he begins his instruction, offering several reasons why you should consider it. Many times incorporating bent wood in a project is not so much a necessity as it is an aesthetic. Sometimes it is used to elicit a response, triggering sensory reactions in a person that linear design just won't effect. It is often expressive, and used solely to make a statement through a piece of furniture or art.
To bend wood successfully, you must understand its underlying Properties. The cut of wood is paramount. Quartered stock yields pieces readily adapted to bending, whereas plain sawn wood can split or break under stress. Obviously straight-grain is most desirable, though tight-grain (especially old-growth stuff) will be much more difficult to manipulate. According to Marc, several species suited to bending are ash, oak, and walnut. A few with average bending properties are poplar, beech, and birch. Poor bending woods are any softwoods and those that are highly figured. Another factor that must be considered is the force imparted on the piece once bent. Keep in mind that inside curves are subject to compressive forces, while outside curves are held in tension - where most failures occur.
Bending Jigs are an essential component to wood bending operations. No, I'm not talking about the two-step you may do when a favorite song hits your ears! These are extremely strong, stable, durable forms employed to mold a piece of wood so that it conforms to a shape mirroring that of the form. Jigs are typically constructed of MDF or particleboard - inexpensive materials that are relatively easy to cut, and can withstand a good deal of repetitive use. They can also be laminated to form larger molds capable of supporting wide boards during bending. Marc finds it's convenient to wax forms prior to use. This tends to preserve it as sticks are clamped in place. It apparently does not adversely affect board surfaces during final finishing.
At some point you must consider which Adhesive to use; initially, for thin strip lamination, or during final assembly of thick stock. Simply put, all modern glues are far superior to those of years ago. Manufacturing processes, controlled environments, etc. contribute to formulation of excellent adhesives. However, that doesn't necessarily mean anything will work for securing bent-wood projects. Marc works from a glue-chart, which complements his explanation of how different glues are made, unique characteristics of each, open- and cure-time, etc. He often works with regular wood-glue, though Urea-Formaldehyde is his choice for laminates.
Mark uses a Steam-Box to prepare his wood for bending, but it's relegated to outdoor use only!! His setup is similar to others I'm sure you've seen. A rectilinear box constructed of plywood, with internal dowel rods that suspend stock within the steaming chamber. His source of heat is a propane tank, and steam is supplied from ordinary tap water. Factors to consider while bending are;
After his demonstration with the steam box, Marc gives a quick lesson on hot-pipe bending. This is a metal pipe, approximately four inches in diameter, which is heated with an internal flame (typically a propane torch). Considered an "old-time" technique, it leverages the apparatus to serve a dual-purpose; it conveys heat directly to thin, wet stock and doubles as the form to coax stock into a curved shape. Shaker oval boxes are common examples of products formed by pipe bending.
Though steaming may be what most think of for bending stock, several other methods can be employed. Kerf-Cut Bending is a method of cutting kerfs in the back-side of a piece to render it pliable. This has its place, though kerfs can telegraph through to the finished side, especially on tight radii. This method is best left to long, "slow" bends. And example might be to make curved sides for a sideboard table. Another technique that uses solid stock is Thin-Wood Laminate Bending. I've already mentioned this method, which eliminates both the steam-box and unsightly kerfs. Thin strips of wood (usually an 1/8" or less thickness) are glued and clamped together to form an homogenous piece of bent wood. But, this can be time-consuming since woodworkers usually resaw thick stock to make their own laminate strips.
This pretty much describes every key topic Marc selected for his instruction. Picture quality of this DVD matches that of others I've seen from Mr. Adams - pretty darn good. It runs approximately 70 minutes in length, and touches on just about everything you need to know for bending wood. As with Marquetry, I find this method of working wood quite fascinating. It breaks the boundaries of standard linear cutting, routing, and shaping, and lends a whole new realm of creativity to our craft. This video should be available for checkout at the next general member meeting.