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Clamps, specifically hand-screw, bar, spring, strap, pipe, and C-clamps remain the basic tools on which any workshop relies, used to hold assemblies in position while glue cures or while nails or screws are put in place.
Clamps are immensely helpful – even essential – in performing certain tasks. Yet they aren’t foolproof. Clamps can be tightened too tightly, exerting so much force as to mar or even break elements being assembled. And some clamps are just right for some jobs, but ill suited to others. Plan ahead and select your clamps carefully.
When acquiring clamps, you might also consider some of these possibilities, as well as the more traditional ones mentioned earlier.
Frame Clamps. As the name suggests, picture frames are the usual use for these clamps. Yet other clamping and gluing work that involves fastening mitered corners is also performed with frame clamps – tasks like making windows and cabinet doors.
The frame clamp consists of four brackets that are positioned at the corners of the frame or other object to be clamped. These brackets or corner blocks hold the adjacent pieces of the frame perpendicular to one another and are then tightened. The tightening mechanism varies: It may be a cord or web with a lever and ratchet device like that on a strap clamp. Or it may consist of a more elaborate steel mechanism of threaded rods and nuts.
Corner Clamps. Miter clamps, as corner clamps are also known, allow you to glue a single miter joint (rather than four, as with a frame clamp). The corner clamp has a fixed right-angle fence that will hold pieces on the inside of the corner. On the outside are adjustable screw- driven “feet” that are tightened to hold each piece in place.
Lever Cam Clamps. These have wooden jaws with cork faces. They are gentle but surprisingly strong, relying upon a cam action to tighten the sliding lower jaw to the fixed upper jaw. Lever cam clamps are suitable for veneer work and general light-duty gluing, as their frequent use by makers of musical instruments suggests (as a result, they are also known as instrument-maker’s clamps). Their light weight and cork clamping surfaces make them suitable for quite delicate work. They’re sold in a range of sizes, with maximum jaw openings that range from just under eight inches to as much as thirty-one inches.
Grip-Drive Clamps. Also called quick-grip bar clamps, these feature a relatively new design and are very easy to use. A trigger lever releases the bar so that the mouth of the clamp can be slid open or closed; the handle is squeezed to tighten the clamp. Removable pads on the jaws protect the workpiece being clamped.
Trigger clamps come in a variety of sizes, ranging from six-inch to thirty-six-inch jaw openings. They’re very handy all-purpose clamps: With their padded jaws in place, they can do delicate work; without the pads, their grip is solid and direct.
Clamping Techniques. With most kinds of clamps, the same rudiments apply. Starting by setting up your work on a flat, level surface. And always do a dry run first, without glue. Go gently as you clamp: Make sure the workpieces are square (if you’re using more than one clamp, lighten them alternately). Use leather or hardboard pads to protect your work from metal clamping surfaces. Don’t tighten too much.
Apply the glue to both surfaces to be glued. Enough glue should be used to coat the joint area thoroughly. When the joint is clamped, a little glue should be squeezed out (if none appears, there probably isn’t enough glue for a strong bond). Too much glue doesn’t make the joint stronger, but it does add the time required to clean up the mess. Wipe off excess glue immediately. Use a paint scraper to get most of it, and follow with a damp cloth. After the glue dries, a hand scraper is the best choice for removing the dried residue.
Clamp Care. Most clamps are sturdy, utilitarian tools, and a minimum of care is necessary to keep them functioning at their best. When not in use, clamps should be stored, preferably on a rack away from dampness. To prevent rust, rub them occasionally with a rag dampened with machine oil.