How to Mount a Bar Clamp
Bar clamps or parallel-jaw clamps have one fixed jaw or head, and a second jaw that slides along a metal bar. They are used to hold parts together parallel to one another or at right angles during assembly, before and after gluing and before securing fasteners. Before gluing, bar clamps hold pieces together during accuracy checks. Traditional bar clamps are available in 6-inch to 36-inch lengths. A new one-handed-release, 50-inch version is also available.
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Things You'll Need
- Clamping blocks
- Tape measure
- Straight edge or spirit level
- Adhesive
- Fasteners
Instructions
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1
Place the items to be clamped in their correct positions. Do not apply any adhesives at this point, because you may have to adjust angles or refashion pieces if anything is out of alignment or incorrectly cut. The process is known as dry-clamping, and will save you from having to scrap an entire project if it is assembled incorrectly or uses parts that were not cut to specifications.
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2
Slide the movable jaw along the bar until there is enough room between both jaws to fit the clamp across the items.
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3
Position the clamp so that the jaws are on the left and right side, front and back or top and bottom of the item to be clamped.
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4
Place a clamping block between each jaw and the surface of the item to be clamped if your clamps do not already have protective pads.
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5
Slowly tighten the jaws of the clamp until the clamping blocks are making full contact with the item surface and the parts to be clamped are in full contact with one another along the joint. Stop tightening if the jaws bite into the clamping blocks.
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6
Place a straightedge across the parts you just clamped to ensure that they are not being bowed by too much pressure, advises woodworker Ian Kirby. Loosen the clamps to relieve the pressure or reposition the clamps so that one faces one direction -- up, down, left or right -- and any others face an opposite direction.
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7
Perform accuracy checks, such as measuring corner angles, diagonals and the lengths of each parallel part, to ensure that all corners make 90-degree angles and all paired diagonals and parts are equal lengths.
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8
Remove clamps and apply adhesives between parts as needed. Replace all clamps and perform all accuracy checks again, adjusting clamp position and pressure as needed.
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9
Remove clamps for the final time after adhesives have dried and all fasteners have been secured.
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Tips & Warnings
Softer woods, such as black cherry, black walnut and Ponderosa pine require 250 to 300 pounds of clamp pressure per square inch, while harder woods such as red oak or sugar maple require 450 to 600 pounds per square inch, advise the editors at the Fine Woodworking website.
References
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