Clamps & Cramps

Clamps, also known in traditional carpentry and cramps, are a range of tools that are designed for holding and aligning components together during carpentry operations and glue ups. They can also be used to push or pull components together. There are a variety of different styles of clamps that are available for use in construction, with an infinite number of possibilities for their use. More than just a clamping tool, these clamps can be used as an extra pair of hands when working alone, with their utility being limitless. Here is a rundown of the most common styles of clamps used in woodworking and site carpentry, focusing on their construction and intended use.

Sash/bar cramps

Sash cramps are long clamps that are used for clamping together large workpieces. The cramp is made from a long “T” shaped rod with a fixed, screw-actuated pad at one end. An adjustable stop can be moved up and down the bar, being held in place with a pin at incremental holes drilled along the bar. A workpiece is placed between the two secured points, and the screw is tightened to clamp the material in between. Many different lengths of cramps are available for use in a variety of applications. These large cramps are used for gluing together wide boards, or many boards, as well as pulling together the joints of wide components such as doors, and sash windows.

Mitre clamps

Mitre clamps are a category of clamp that are used for holding two components together at right angles, typically whilst they are being glued together. Some styles feature a solid body with two screw actuated clamping surfaces fixed to them. The components are inserted into the body and the screws are turned to tighten them in place. Other styles feature a single screw with a 90-degree jaw that pinches both components together. Once the components are securely held together, nails, screws, dowels, and other hardware can be installed to keep them together.  

F clamps

“F” clamps are smaller, general-purpose clamps that are useful in most lightweight clamping applications. The construction of the clamp features a bar with a fixed stop at one end. Held captive on the bar is another sliding stop that also features a screw actuated jaw. To use the clamp, the item or components being clamped are placed between the jaws. With the fixed jaw tight against the workpiece, the sliding jaw is slid up the bar to meet the component, and the screw is advanced to tighten the clamp. As the clamp is tightened, the sliding jaw is offset slightly, with the bar also flexing a small amount, locking the sliding jaw in place with friction. The basic mechanics at play in the design of these clamps allows an incredible amount of pressure to be exerted between the jaws, in comparison to other styles of clamps.  

C clamps

C clamps are fixed jaw clamps that feature a single screw actuated jaw. The clamping width of each clamp is determined by the distance between the C shaped frame. Whilst they can be used for most general workshop activities, as well as in woodworking, these clamps see most of their use in metal fabrication and welding.

Floor clamps

Flooring clamps are specially designed clamps that are used for installing traditional floor boards. The clamps feature rotating, toothed, circular grippers that are placed around the floor joist perpendicular to the floorboards. A screw actuated jaw can be advanced out the face of the clamp. As the screw is advanced and the jaw meets the floorboards, the force created causes the rotating gears to pinch the sides of the joist and exert pressure onto the boards. This clamp is therefore used to tighten the gaps between multiple rows of floorboards before they are fixed, in the typical event that the boards are not perfectly straight along their length.  

Trigger actuated clamps

Trigger actuated clamps are “F” style clamps with a moving jaw that is actuated by a trigger. When the trigger is pulled, the moving jaw advances up the length of the bar towards the fixed jaw at the end. With a workpiece in between the jaws, the trigger can be pulled until the jaws are securely tightened. To release the moving jaw or move it freely up the length of the rod, a spring release tab is pushed, freeing the friction-based mechanism.  

Whilst these clamps are very handy in their design, they are not able to exert as much force as other screw actuated clamps. The one-handed operation of these clamps allows them to be used as holdfasts when installing timber components in site applications. They can be used as an extra pair of hands. Some brands feature a removable jaw that can be flipped around to the other end of the clamps. This reverses the direction of the jaws and trigger pull, allowing the clamps to push components apart as opposed to pulling them together.  

Spring clamps

Spring clamps are lightweight, spring powered clamps that behave in the same way as a washing peg. When the handles are squeezed, the jaws open, allowing small workpieces to be placed between them. When the pressure is released, the spring inside the clamps pushes the jaws back together again, exerting force onto the workpiece. They can be used for many general purpose clamping and holding applications. Due to the limited strength of the spring inside the clamp, they are not able to exert an extreme amount of pressure like other clamps can. That being said, they are perfectly apt for holding small components together during glue ups.  

Band clamps

Band clamps are ratchet style clamps that operate on a long synthetic band. In short, a fixed mechanism features a receptacle for a long synthetic belt. As the mechanism is actuated, the belt is fed through it, shortening the circumference of the belt. As it comes tight, components inside the loop are squeezed. Four right angle attachments are typically located freely on the belt and can be moved to apply pressure to the corners of square components that are being clamped.