Clamping mitered corners

[Ellen Benkin]

I'm making some bookcases with mitered corners and need to know how to clamp them. I know how to do small boxes with masking tape, but these are too big and heavy for that. I don't want to mar the wood with nails. Any suggestions?

I wanted a clean look at the corners but I don't think I'd do miters again. Everything is more difficult including keeping the edges from chipping.

[Lee Schierer]

You can use long strips of nylon strapping tape perpendicular to the joint to hold the joint together while you apply clamps in both directions at each corner. Make sure you check for square and alignment as you alternately tighten the clamps. you can also cut a slot across the face of the miters and make it a splined miter joint which will help maintain the alignment and add to the strength. Remember to use lots of glue as you will be essentially gluing end grain and the wood will soak up the glue. Some like to "size" the joint with an application of diluted glue to the miter surfaces before applying the final glue for assembly.

[Alan Schaffter]

You can do like Tommy Mac did on a recent show- glue temporary clamping blocks on each side of the corner. Once the glue-up is hard remove the blocks and plane the ends to get rid of any marks left by the glue. Though it won't hold the glue blocks as well as yellow glue, you can use hot melt glue which will pop off easily and completely when you are done.

Are your reinforcing the miters with splines or biscuits? That will strengthen the miter joint and keep it aligned.

[Ken Garlock]

Good day Ellen.

There is always a use for clamping squares. Several years ago I bought a set of machined aluminum squares from woodpecker (http:///www.woodpeck.com/clampingsquare6.html) It seems that they are one of the usual working tools when I start to assemble a project. Yes, they are a little expensive, but they last several life times.

[Matt Day]

How about a ratchet strap? I've got some little Rockler add ons that work well with the strap.

[glenn bradley]

You can do like Tommy Mac did on a recent show- glue temporary clamping blocks on each side of the corner.

This is what I do but, I use double stick tape or transfer film. The tape I use gets pretty comfortable where it is if you leave it over night so I generally set a timer to remind me to come take off the clamps and knock the blocks off after a couple hours.

For woods I don't want to glue or tape to for whatever reason, I have made up sets of these for different needs:

[Chris Padilla]

I've used glue blocks as suggest by both Glenn and Alan but I've always used a piece of brown paper bag (grocery bag) between the block and cabinet. Doing this makes knocking the the glue block off later much easier and cleaner.

I'd also suggest reinforcing the mitered joint with biscuits, splines, dowels, dominos or perhaps even pocket screws (unless they will be seen). These devices may also aid in holding the joint together as you fuss with clamping but be careful in using them as they can woefully misalign the joint as easily they align it! :)

[Carroll Courtney]

Never use them,but they sure look like they would work----Carroll
http://www.miterclamp.com/

[Paul Johnstone]

Another option is to use permanent glue blocks somewhere that is not conspicuous.
For example, under the bottom shelf. Maybe you can fit one above the top shelf as well. I will do this, and use screws to
help hold things together.



Never use them,but they sure look like they would work----Carroll
http://www.miterclamp.com/

I have these, and they are awesome for clamping up trim or "picture frame" type stuff.

[Rick Fisher]

Dont mean to segway but this is a great application for a domino.. I used to hate clamping miters, a single domino makes it a breeze..

[Steve Griffin]

Are you sure you can't use the tape method? As long as you can hold the joint open in a flat plane, you can use packing tape.

It's easiest if you can miter and glue up your corners before assembly. But there is no "size" limitation to the tape method.

Also, for some types of wood, a mitered corner isn't the always the best. Careful grain matching a perfect butt joint can often yield a more invisible joint than a difficult miter situation.

-Steve

[John TenEyck]

I built this fireplace mantel last year. Every edge/corner is mitered. I used bisquits for alignment, and it pulled together perfectly with just clamps. It took quite a few clamps, and I had to check to be sure everything was square, but it wasn't very hard, and the joints were perfect. This was the first large project I had done with only mitered joints, and I was pleasantly surprised how easy it went.

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[Ellen Benkin]

Thanks everyone for the great suggestions.

I bought two sets of these corner clamp gizmos from Woodcraft http://www.woodcraft.com/Product/2003719/1535/Corner-Band-Clamp.aspx

Since the bookcases were 8" deep I needed two band clamps. After a little testing these were easy to set up and worked perfectly and I would highly recommend them.

I also used Gorilla Glue and it allowed for a long open time to get the clamps set and the miters aligned. It was difficult to get the squeeze out off the wood, but in the end everything is even and square so I'm happy.