Specialty Clamps for Tricky Glue Ups
Bringing flat, square edges and faces together on a woodworking project isn't rocket science. A collection of bar, pipe and screw clamps can accomplish these sorts of day-in-and-day-out shop assemblies with ease. But what about those circumstances where you need a secure hold on curves or angles, or a clamp must push rather than pull? Here's when a few specialized clamps are not only practical at glue-up time but could even prevent a trip to the emergency room. Consider the following woodworking scenarios and some handy clamp variations that'll do the job when others don't.
Covering the Spread
While you probably spend most of your time assembling projects, sooner or later every woodworker encounters the occasional repair job — and quite often that involves some creative disassembly. A common furniture failure involves broken joints where stretcher spindles separate from chair legs. Tension and racking from use is tough on these cross-grain glue bonds. But, if just one stretcher breaks free and not the others, how do you separate them all to make the fix? Here's where knowing your glue chemistry can really help — and so can having a few bar clamps that act as spreaders. Bessey's Revo Junior clamps, for example, have a removable clamp head that can be reversed on the bar to direct pressure away from the fixed head (see Photo 1). A uniform and controlled application of pressure, parallel to the chair stretcher, will often separate the joints neatly and without resorting to pounding, twisting or other brute force.
Applying solid-wood banding to the edge of a narrow piece of sheet material is a simple operation with conventional straight clamps. The circumstances become more complicated, though, when that melamine or plywood sheet is 6 ft. long or has a curved edge. Sometimes your bar clamps just won't reach, or a parallel grip is compromised, and that's when three-way edge clamps really shine. Rather than needing to span a panel's width or length, they grip it through the thickness, then enable you to apply lateral pressure with a third screw head to press banding securely against the substrate. While you probably won't need edge clamps on a regular basis, the light-duty varieties are quite affordable — and you'll appreciate having at least a half dozen or more of them at the ready for that tricky glue-up situation.
If cutting perfect miter joints isn't difficult enough, a poorly devised clamping strategy can still leave you with a gap along the seam and — equally frustrating — an out-of-square assembly. There are clamps made to help you draw these persnickety joints tight and perfectly square. Some feature a single screw that draws an angled inner head against a fixed outer head, to accommodate workpieces of various thicknesses. Other styles use a pair of screw jaws instead. These specialty clamps will help close a variety of miter joint styles, but they're most beneficial in "glue only" situations when the joints aren't interlocking and self-aligning.
Angled joints that don't form a square corner present their own assembly challenges — and you'll learn this the first time you need to glue up a closed shape having more than four sides. You need a clamp that can surround the figure and draw it together with pressure equally distributed at every corner. Here's where a couple of band clamps are not only helpful but practically essential to taming these non-square joints. Band clamps are also useful for drawing four-sided, mitered frames together when the edge thickness is reduced by substantial contouring and the clamping surfaces are diminished. Most strap clamps have quick releases or a crank to draw up extra strap length; a screw handle controls the final clamping pressure.
Of course clamps aren't just for glue-ups. They're equally vital at the router table, shaper, table saw or virtually any machine tool where cutters pose the risk of serious injury. A pair of toggle clamps, for instance, can turn a potentially dicey tapering operation into a safe, controlled technique. Any time you need to both immobilize a workpiece and present it to a spinning cutter, you should be thinking about workholding options first. Toggle clamps can direct force either downward or forward, depending on the style. Consider them when designing your workholding jigs, and they'll help you keep all ten fingers where they belong ... on your hands.