An old adage passed around by sage woodworkers is that one can never own enough clamps. It is quite true that a woodworker's collection of clamps increases steadily with their length of experience. It's not uncommon to see a woodworking shop with many styles of clamps, and many sizes of each. The collection can include one-handed quick clamps for securing an assembly when you have only one hand free; spring clamps that work great when steam-bending a piece of wood; and light-duty bar clamps for holding small assemblies. Each type of clamp has its advantages and designated uses.
Bar Clamps vs. Pipe Clamps
When it comes to larger jobs, such as making a glue-up for a tabletop or a raised panel cabinet door, you're probably going to need a longer clamp. Traditionally, this would be the domain of the large bar clamp—a flat, steel rod with a secured jaw on one end and an adjustable jaw on the opposite end.
But bar clamps can be quite expensive A set of two 24-inch and two 48-inch bar clamps can approach $200. That's a bigger outlay than most beginning woodworkers can afford, especially when you consider that you may well need 10 to 15 bar clamps to cover all the required sizes.
Pipe clamps offer a good alternative to bar clamps. A pipe clamp is a two-piece kit that attaches to a length of inexpensive threaded galvanized pipe or black pipe in whatever length you want. There are clamp sets designed for both 1/2-inch diameter and 3/4-inch diameter pipes. With two to four clamp kits and a large handful of pipes in various lengths—a total investment of less than $75—you can be ready for almost any clamping duty.
How Pipe Clamp Kits Work
Each pipe clamp set contains two parts: a stationary foot that includes an adjustable clamp plate, and an adjustable foot with a flat plate that adjusts along the length of the pipe. After adjusting the clamp so the workpiece is loosely clamped between the foot and the adjustable head, the clamp plate is screwed down, applying enough pressure to hold boards securely in place as a glued-up joint hardens. The most common use for pipe clamps is to glue up individual boards to form a large table-top or another flat surface.
Pipe clamp sets can be cost as little as $7 each when purchased in bulk, but even the best pipe clamp set rarely costs more than about $20 each.
Galvanized vs. Black Pipe
There are two acceptable types of pipe you can use with pipe clamps: galvanized pipe and black steel pipe—the same type traditionally used for gas lines. Either will work fine, but the black pipe is less expensive, which makes it the preference for woodworkers on a strict budget. That being said, be aware that black pipe can leave stains on the surface of your boards, so you'll want to take some precautions if you are planning to sand, stain, and top-coat the wood.
Avoiding Common Problems With Pipe Clamps
While the cost savings and versatility of pipe clamps certainly are an advantage over bar clamps, there are some drawbacks:
- Pipes may bend under pressure, particularly at lengths over 4 feet. You can minimize this problem by using 3/4-inch rather than 1/2-inch pipes, and by using multiple clamps on both sides of the glue-up to distribute the pressure.
- Another problem, particularly on multi-board glue-ups, is that applying too much pressure can cause the boards to deflect, creating bowing. To solve this problem, alternate clamps on both sides of the workpiece to spread out the pressure and keep the workpiece from bowing one way or the other. Use just enough pressure to tighten the joint, and try to tighten all of the clamps evenly as you go.
- Black pipe can sometimes stain the wood that it touches. There are several possible solutions. First, you can simply leave space between the pipe and the boards in the glue-up. While this space keeps the pipe and boards from contacting one another, it can lead to bowing. A second method is to place a scrap piece of wood between the boards and the pipes. This idea works well as long as the scrap is of a similar species to the boards being clamped, but it can be problematic if the scrap board becomes glued to the assembly. A third option is to slide a sleeve of 1-inch-diameter PVC pipe over the black pipe. Since PVC doesn't bond well to wood glues, this is an inexpensive and effective option.