Clamping and Fastening Mitered Cabinet Corners

      Advice on tape, clamping jigs, and the like for holding mitered corners in place for careful, accurate fastening. July 13, 2010

Recently, I began to incorporate 3-7/16" wide mitered corners with applied reeded and roped half columns and capitals into my bath vanities. They look great and customers usually opt for this style. However, the usual methods (two 45's on the mitered board, or four 22.5's on both board and stiles) are difficult to keep aligned with traditional corner miter clamps.

Screws counter-sunk through the adjacent stiles usually don't have enough purchase (3/4" stock) in the 45 degree miters unless the edges are left proud and planned fair after. And while the 22.5 degree miters are relatively better in this regard, there are extra cuts involved along with the usual clamping difficulties.

Has anyone had any suggestions that would save time (and aggravation) constructing this type corner? I haven't tried the locked miter 90's or 22.5's bits or splines yet, mostly because while helping to keep the joints aligned, the clamping issues remain problematic.

Forum Responses
(Cabinet and Millwork Installation Forum)
From contributor R:
Scotch or 3M #355 V-fold tape works wonders. You can apply it to a finished product, it is very strong and won't stretch. To remove after the job is done, use naphtha; it won't affect your finish. Naphtha dissolves the adhesive.

Put wood pieces face up and butted together, put a couple of small pieces across the joint to hold together, last put a strip down the entire joint. Flip over, put glue in the open joint, and fold. The use of corner blocks will keep the angles true while drying.

From the original questioner:
Thanks! You gotta love a good, strong adhesive tape! The method you describe is similar to what I have been doing. Although I have been using turners tape instead and making several small tape hinges across the joint and not vertical to the seam, as you suggest, and tacking the very edges with glue.

Ironically, the last two cabinets currently under construction, I had run out of turners tape, and substituted duct tape. (It is truly amazing how much I rely on turners tape and how much of it I use!) These have proved the most problematic... Mostly the tape I guess, but also the boards were slightly bowed.

In the past I had constructed a back-bracing of sorts, so that I could pull the joints in tight with screws. However while working well, the time and materials spent on constructing the bracing led me to find a more efficient way.

I'll give your method a try on the next units. It seems that the quality of tape used is critical and I suspect this might work even with slightly bowed stock.

From contributor D:
If this is something you're going to do a lot of, you should make some type of form to clamp to. How about trying some 23 ga. pins too?

From the original questioner:
Thanks! I've mulled over some possible clamping forms, ala Andy Rae's plywood 22.5 degree clamping cauls, for instance. But just about everything I've seen has relied on having access to the stile from a face frame or side stile. While my usual glue-up method has completed raised panel sides rabbited to the cabinet bottom before gluing the mitered columns on.

I shot some brads into the tops and bottoms of the mitered column where they would be hidden by trim molding, say, but I shy away from having to use wood filler in visible locations (small though the brad heads be). And brads generally work better if the joins are pulled up already.

The mitered corners tend to be popular right now, especially in kitchen islands, corner cabinets and such. It's hard for me to believe that someone has not developed a good 22.5 miter clamping system. Someone suggested a web clamp and gluing several joints at once. Though I question the technique on large carcass construction (I'm usually busier than a one-arm octopus gluing just a few joints at once).

I think that if I do come up with a workable jig or clamp, I'll market it and make a gazillion dollars. Then I could retire! (Just kidding... wood dust is in my blood and I probably would not survive long without it.)

From contributor U:
I use green painters tape; it has enough tack to hold and enough stretch to clamp the miters. I tape across the joint to pull it together and then along the joint to act as a hinge, glue and fold.

From contributor K:
Have you tried strap clamps? Or quick-dry (30-60 seconds set time) glue?

From contributor S:
For the 45 deg corner, I cut one side at 45 and the other at 90 and use pocket screws and line up the inside edges and screw it, then plane off the overhanging 45 degree miter's point.

From contributor J:
Try some commercial grade contact cement. Spray glue in an aerosol can. I use WhisperCon. Gets used for crown, lightrail, skins, etc. Holds great, no wait time, and a few 23g nails and you can keep rollin'.

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