A glue-up can be ruined by two perfectly aligned boards slipping out of a square position at the moment you reach for the next clamp. While corner clamps may seem like a handy tool to have in your shop, corner clamps solve a frustration that is very old in the world of woodworkers; the frustration of getting the corners of a joint to stay tight, square, and not come apart while the glue works to secure the two pieces together. If you get the right corner clamp, you will have zero fuss in your glue-ups and your finished projects will feature crisp, even corners.
However, if you use the wrong corner clamp or a corner clamp constructed with cheap materials, you will spend more time fiddling with the wood you are joining than you would of like to spend building the project altogether. There are a few different styles of corner clamp, and some is used for more delicate woodwork than others. For instance, there are corner clamps that are used for more delicate picture frames and others that are very strong and used for heavy cabinetry work.
There are even a few clever designs that allow one person to complete the job that would otherwise require two people to gain the proper leverage to clamp the corner of a project. The following sections describe the different corner clamp styles and the use of each in the workshop. These descriptions range from the corner clamps that you will use the most to the more specialized corner clamp designs that help you solve the most difficult problems with your glue-ups.
Different Types of Corner Clamps for Woodworking
1. Screw-style Corner Clamp
The screw-style corner clamp is likely the first clamp that most woodworkers will purchase. These clamps come as a set of four, with each set including two screws. The screw-style corner clamp features cast iron jaws to ensure that the joint remains square even under heavy pressure.
Additionally, one screw will even the thickness of the wood and the other to clamp the two pieces together. While it is a slow process to even the wood with the clamp, the control that the woodworker has gives this clamp a reputation for even the most difficult projects. The screw-style corner clamp is notable for being able to clamp on wooden stock of different thicknesses.
By placing the deeper jaw against the thicker stock of wood, the shallow clamp will naturaly even itself onto the other, thinner piece of wood. This evenness of the clamp will prevent the headache of one piece of wood riding up from the other. However, there is a tradeoff in using this clamp, time.
There is no rush in using a screw-style clamp because it requires so much careful positioning of the wood. Where production woodworkers or those building larger projects may turn to the ratcheting band clamp. With four separate clamps, woodworkers can save time.
2. Ratcheting Band Clamp
The band of the clamp can be made out of nylon or fabric and features plastic or metal corners that protect the edge of the wood. The ratcheting clamp allows for even pressure around the clamp and allows one person to clamp a project of any complexity without the need for another individual to assist in the clamp placement. Ratcheting band clamps are especially helpful for woodworkers who require even pressure on the joint rather than brute force in each corner.
Additionally, bands of the clamp will even a joint that is slightly out of square before the glue hardens. However, care must be taken when using a ratcheting clamp because the band may mar the finished wood if it is used too tightly. A layer of masking tape or cardboard can be used under the wood to protect it.
A woodworker who has used a ratcheting clamp for picture frames will find there love for the clamp hard to kill. Pipe corner clamps may look crude, but they offer woodworkers very accurate results for a low cost. Made up of two right angle brackets that are placed on black iron pipe, the two ends of the clamp can secured with bar clamps or pipe clamps.
3. Pipe Corner Clamp
The benefit of the clamp is that the woodworker already owns the metal pipes that are required for this clamp setup so the cost to upgrade a woodshops tools is minimal. Woodworkers who create many large boxes or who perform carcass work with their projects will find that the pipe clamp allows them to place the corners of the clamp wherever the woodworker would like the clamp to be positioned. The pipes allow unlimited reach for the clamp.
The one downside for pipe clamps is in the setup of the clamp. It is necessary to cut a piece of black iron pipe to the proper length and thread the end. Alternatively, woodworkers can purchase pre-threaded sections of pipe.
Once they have a few lengths of pipe that they know they will need, the clamp setup becomes addictive for woodworkers. The next style of corner clamp to discuss is the aluminum alloy clamp with quick release levers. These clamps feature two adjustable fences and a trigger clamp that can be closed in a few seconds.
4. Aluminum Alloy Clamp with Quick Release Levers
The best aluminum alloy corner clamps also feature a few small pads of nylon material to avoid marring the wood, and an adjustment screw for each fence so that the clamp can be set to a perfect 90-degree angle. Speed is the most important feature of these clamps. The clamp can be positioned in the corner of a joint, and the clamp can be opened and closed before the first piece of wood begins to move.
These clamps are used for small production runs of boxes. However, most clamp designs have a limit to the thickness of the wood they can handle. Most aluminum alloy corner clamps has a maximum thickness of two inches.
A final design for corner clamps are the specialized miter clamps with cam action jaws. Unlike corner clamps that push on the inside faces of the wood, the specialized miter clamp design grips the outside corner of the joint. Additionally, these clamps pull the two pieces of wood together from the show face.
5. Specialized Miter Clamps with Cam Action Jaws
The best miter clamps feature hardened steel pins that grip the wood without marring it. These types of clamps are used when the outside corner of a joint must be perfect, such as for a high-end picture frame. The cam action of these clamps means that a small turn of the clamp produces alot of pressure.
However, when the clamp is closed, there will be tiny pin marks on the wood. These marks will dissapear when the wood is finished. However, on raw wood, a few extra minutes of sanding will be required.
The next corner clamp that will be discussed is the parallel jaw corner clamp. Though they may look like ordinary bar clamps, these features two wide jaws that will remain parallel to each other even with heavy pressure on the clamp. Many of these clamps have a T-track on the clamp that allows other accessories to be added to the clamp.
6. Parallel Jaw Corner Clamp
Because the clamp has such wide jaws, the clamp will distribute the pressure on the joint rather than applying it to a single point of the joint. Cabinetmakers who often work with face frames or web frames will find that the clamp allows one clamp to even a joint while leaving the woodworker hands free to drive the screws or apply glue to the joint. Additionally, because the clamp features such wide jaws, it will not create a problem with thin stock of wood cupping under pressure.
If you have the budget for only one clamp that will pay for itself over many years of use in your shop, the parallel jaw clamp will be the best purchase. Vacuum corner clamps are used in the high-tech workshop and solve problems that the mechanical corner clamps cannot solve. Rather than metal jaws, the corners of the clamp feature suction pads that are connected to a vacuum pump.
7. Vacuum Corner Clamps
By removing the air from the clamp, the pad features hundreds of pounds of pressure that will clamp the two pieces of wood together. Vacuum corner clamps are of most assistance to woodworkers who work on projects with curved or irregular joints since a mechanical clamp cannot find anything square to push against. While the setup for a vacuum clamp may take more up front planning, vacuum corner clamps will create excellent results for woodworkers who work on delicate veneered or complex picture frames.
Additionally, because the clamp does not feature any metal in the clamp in the way of the wood to clamp, a router or sanding clamp can be used on the joint without moving the clamp itself. While vacuum corner clamps may feature an additional cost for the clamp and the vacuum setup, any production shop or woodworker seeking perfect results will appreciate the clamp purchase. No matter the corner clamp you choose, the best results will be had if the woodworker can anticipate problems with the joint.
A dry run of the glue-up with the actual corner clamps will reveal any problems with the joint. The best woodworkers will own a few different corner clamp brands and will know which brand to use for what project. These woodworkers will find themselves using the corner clamp without thinking about it and will always have tight, even corners.
Such a skill will change the way that the woodworker looks at wooden stock.
