Miter Clamps vs. Corner Clamps : What’s the Difference?

Many task in woodworking and carpentry require two pieces of wood to be joined at 90°. But not all corner joints are made equal and it is important to find the right tool for the task. That is where the decision between miter clamps vs corner clamps comes into play. At first glance they can appear to do the same thing, but there is an important distinction. Let’s have a look at the many options available on the market and explore how they differ.

Corner Clamps Explained

Type 1 – Corner Braces

Corner braces, also referred to as corner blocks, are useful devices that will help position two intersecting boards at 90° to allow for square assembly. Some models also allow for ‘T’ joints and cross joints in addition to corner joints. Many models are simply metal or rigid plastic L-shapes brackets that allow the user to apply separate clamps to fix the boards in place. They are essentially a square designed to clamp directly to the work pieces. These are especially useful when assembling large items with multiple joints as you can use multiple braces to position the pieces perpendicular to each other during complicated glue-ups.

Type 2 – Corner Clamps

Corner clamps differ from corner braces in that they incorporate the clamping mechanism into the tool. There are literally dozens of different models from the higher-end Bessey WS-3 Angle Clamp That allows clamping of corner, T and cross joints of varying thicknesses up to 4″ in width, all the way to the very basic models that are made from rigid plastic or stamped steel.

There is one major downside to these corner clamps; they do not apply any pressure to the joint itself. Whether it is a miter joint or a butt joint, these clamps are only effective at holding the pieces square to each other. Even the expensive models that incorporate the clamping do not apply any pressure to the joint itself. So their use is really limited to joinery where you are using another method to securely clamp the joint. That may be glue, dowels, biscuits, nails, screws or pocket holes.

Miter Clamps Explained

A miter clamp is used where a corner joint (typically 90°) is joined with a miter – that is two boards cut at 45° intersecting to make a square corner. This type of joint is often used for aesthetics because the miter joint eliminates the appearance of end grain, and creates a visually appealing corner.

This joint can often be found in picture frames or in box/case joinery. The difficulty with this type of joint is the strength. Because the joint is between two edges cut across the grain, the glue joint is considered end-grain to end-grain, and this is typically the weakest type of glue joint.

It is also often the case the due to imperfections in the wood, or inaccuracies in the preparation of the parts, that miter joints need to be clamped tightly together to remove any gaps in the joint. This is especially critical if gluing the joint will be relied upon for any strength.

This is where the miter clamp comes into play. There are actually very few commercially available options for clamping systems that apply pressure to the miter.

There are 3 main types:

Type 1 – Collins Wire Spring Clamps

• These ‘clamps’ are often used for trim and finish carpentry where tight miters are required, especially on stain-grade products where filler or caulking is not an option to fill gaps. They are made from stiff spring wire and have sharp tips that bite in to the face of the wood to apply a lot of pressure directly across the miter. They can be used on a range of miter angles, not just 90° joints.
• They require a special pair of pliers as shown below in order to expand the wire clamps, then release them them into the joint. These are typically used to apply pressure to the miter while the glue in the joint cures.

Type 2 – Pinch Dogs

• Pinch dogs (Shown Below) are a unique tool that uses two teeth that taper towards a central bridge. They work by tapping the teeth into mating boards, allowing the taper of the teeth to force the boards together. They can be useful where conventional clamps wont work due to the size or shape of the objects being clamped. They apply a lot of force with little effort, and are relatively inexpensive.
• They do have a major downside, however, and that is the holes they leave after being removed. This can often be dealt with by removing the damaged material after clamping, if you carefully plan ahead.

 

 

 

Type 3 – Clam Clamps

• Clam Clamps are unique option, unlike anything on the market. They are a 1-pc clamp typically used for trim work such as door and window casings. The design of this clamp uses four hardened steel teeth along each face of the clamp that, with the turn of the handle, bite into the edges of the wood and force it together, applying very high pressure to the joint face.
• This clamp will also leave small marks in the surface of the wood, so it’s preferable to use them on paint grade trim. But even on stain grade material the holes are usually inconspicuous and can be filled with color-matched wood fillers/waxes. The original inventor of the clamp still sells them directly from his website, although they are also now available through Wood River.

A 3rd option: Frame Clamping Systems

There is another option, which is somewhat limited in use to assembling frames, where there are four mitered corners making up a square or rectangular frame. These are called Frame clamps and rely on opposing side of the frame to apply pressure across the joints. One example made by DCT is shown below.

There are a few other brands available, such as Busy Bee.

The cousin to these frame clamps is the web clamp system. They work on a similar principal, but they use a strap or web that wraps around the frame to apply pressure. They are often fitted with corner braces that are either fixed at 90° or flexible to accommodate a range of angles.

As you can see in the example below – this is a Pony Jorgensen Web Clamp System, and in this case it is clamping a hexagonal form. This type of clamp is very versatile in that it will conform to just about any shape, can apply a good amount of pressure, and can clamp very large objects with very little cost. The downside is they they do not provide much as far as positional alignment or squaring of the assembly, so it is better to use something like a corner brace in conjunction with these web clamps if proper alignment is important.

The Final (and most Interesting) Option

And finally, when you are in the middle of a project and realize you don’t have the right clamp for the task, you do what all woodworkers and DIYers do – you make your own clamps, fittings, jigs etc… I show one example here in my picture frame tutorial video: https://youtu.be/KVrYVrXodow and you can find many others on YouTube. The important part here is to be creative and have fun.

I hope this help clear up any confusion about the many dozens of options and differences between corner clamps and miter clamps. Happy woodworking!

 

 

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