Features and working of a woodworking clamp

The jaws of the woodworking clamp form the actual clamping components of the tool. All hardwood jaws are designed for uniform distribution of pressure over the entire workpiece. These jaws are versatile enough to be able to firmly grip even non-parallel surfaces and irregularly shaped objects. The size of the clamp varies from around 3 to 10 inches. The jaws are most often 90 degree parallel contraptions. The location of the jaws, the rail and the length of the handle derives maximum efficiency from the tool to generate the largest torque possible.

Certain heavy duty woodworking clamps have an approximately 12 inch throat depth, a 20 inch opening and can generate a clamping pressure of around 1550 pounds. A clutch action enables automatic gripping of the object. Poly-clad steel jaws coupled with large sized acme thread provide adequate gripping action with a lower number of turns or cranks required. The clamp moves over a serrated steel rail especially designed to minimize flexing. The tool is designed to ensure that the jaws are always oriented at right angles to the rail. A swiveling rear jaw enables quick adjustment depending on the material thickness. Most clamps have a variable pressure feature which allows the user to adjust the clamping power of the tool depending on the nature of the workpiece and the intended task.

The tool may have a glass fiber reinforced polymer housing which combines light weight with sturdiness. Angle clamps are designed to always align the workpiece at 90 degrees. Miter clamps help in creating angled joints ranging from around 45 to 120 degrees. 

What to look for in a woodworking clamp

The individual clamps are constructed to minimize marring of the workpiece even when the jaws are taut over the object. The jaws are usually glue resistant. Some woodworking clamps can double up as pipe clamps that are used to grip pipes when they need to be either threaded or cut. These clamps usually have plated spingles to minimize formation of rust or other corrosions. Corrugated jaws are stronger and a uniform powder coating eliminates the possibility of corrosion.

A larger clamping surface ensures positive pressure gripping. For added stability, generally a jaw locking system is incorporated (molded) into the sliding arm. A ratcheting clamp minimizes vibrations. Sometimes the die cast jaws are plastic coated to prevent marring the surface of the workpiece. A large diameter pad surface helps to lower the chance of dimpling. A long handle increases the leverage effect and enhances the comfort for the user. The handle is ergonomically contoured, with a soft rubber grip, to provide the user with a comfortable grip, ensuring that the tool can be hand tightened to the maximum pressure the clamp is capable of.

Clamps that have a wider and higher mounted base offer more stability and greater handle clearance for easier maneuverability.  Bar clamps usually are of two types; a balanced T-handle and a sliding pin handle. Some clamps use high tensile strength nylon bands to facilitate the clamping action. One hand edge clamps use a compound screw mechanism to allow single handed use of the tool.

Some reputed manufacturers of woodworking clamps include Bessey, Jet, and Wilton.