Clamping Mitered Joints

[George Bokros]

I am working on a project that will have an inset glass top. I plan to have a wood frame around the glass like building a picture frame. I am planning to put tenons in the joint for strength and alignment. I have considered using those clamps with the pins that hold the joint together. I am wondering if the little divots are an issue to sand out. In the past I have used band clamps but the joint tends to slide out of alignment and is a pain to get perfect.

Questions;

Are those divots very deep?

Recommendations for clamping the joint?

Thanks

[Jebediah Eckert]

I have used those clamps and they do leave a very visible divot. For a picture frame I would just plane the divots out and they were fine, but the final dimesions didn't really matter. I'm guessing it would with your table top.

I mostly use "pinch dogs" for miter glue ups from the back. The "pinch dog" idea was picked up on SMc, but I forget from who. Since then I use them for miters if the project dry fits nice, and the back side doesn't matter, take a look at those.

One I thing I really liked with the pinch dogs is it leaves the ends and face completely exposed so it can be easily checked and glue squeeze out cleaned up.

[Lee Schierer]

I use a picture frame clamp that is similar to this one.
354268
You can accommodate any size rectangle by adding lengths of threaded rod with coupling nuts. For taller structures than a picture frame you might want several clamps of this type. You will also want to check the diagonal measurements as you tighten the clamps to insure that your assembly stays square and to keep the corners aligned.

[Mark W Pugh]

I use a picture frame clamp that is similar to this one.
354268
You can accommodate any size rectangle by adding lengths of threaded rod with coupling nuts. For taller structures than a picture frame you might want several clamps of this type. You will also want to check the diagonal measurements as you tighten the clamps to insure that your assembly stays square and to keep the corners aligned.

What Lee said. I have used the one from Lee Valley numerous times. Easy to set up, and holds the frame together perfectly.

http://www.leevalley.com/us/wood/page.aspx?p=31162&cat=1,43293,31162

[Marty Schlosser]

I use band clamps which have 4 corner blocks to assist in aligning everything. They can also be used with 3, 5,6 or more cornered mitred frames by making custom corner blocks - or by leaving them off entirely. They're the best solution I've found to this challenge.

[Jim Andrew]

I just use my parallel clamps, let the jaw extend past on one side of the joint, and use another parallel clamp at 90 degrees. You can adjust the tightness to flush the corners. Keep a rubber hammer handy. Put 2 clamps on the table, then the frame, then 2 clamps on top.

[Bill Adamsen]

I always think of the Hartford clamps for painted trim. The hardened steel pins really penetrate - the clamping pressure is significant. I only use for clear wood trim if assembled separately and the assembly (I use lamellos) is strong enough to plane the mitered corners. That said, if the clamped surface can be machined afterwards, they would be a good choice. They are a significant investment if you don't already have them, and I rarely see them sold anywhere used.

[George Bokros]

I always think of the Hartford clamps for painted trim. The hardened steel pins really penetrate - the clamping pressure is significant. I only use for clear wood trim if assembled separately and the assembly (I use lamellos) is strong enough to plane the mitered corners. That said, if the clamped surface can be machined afterwards, they would be a good choice. They are a significant investment if you don't already have them, and I rarely see them sold anywhere used.

Whoa, they are a significant investment. $93.50 on Amazon

[glenn bradley]

I use the ones Lee shows for smaller items. For larger frames I use some shop made blokkz.

354277 . 354281 . 354282

354279 . 354276 . 354278354283 . 354280

The last example pic is not a miter but, you get the idea. I just make them out of scrap.

[Phil Mueller]

Maybe I'm just miter challenged, but I haven't found a perfect solution yet. Webs and corner blocks keep me from being able to check the corner and they can get smeared with glue. I've found I can just hold the corner together for a minute or two and slowly release...if it doesn't move, I'm good to go...then carefully apply clamps to hold in place until the glue cures. I usually do the first two corners one at a time, then the last two need to be done together. Not a perfect solution, by any means.

[Bill Adamsen]

Whoa, they are a significant investment. $93.50 on Amazon

Most trim carpenters I know have at least 4 (a fully mitered window) ... locally we get them at Tools Plus which has a box of them near the cash register. With tax they come out to $75 each, $300 for a set of four. By no means the most expensive tool in the quiver, but also by no means an impulse buy.

[Eric Schmid]

I use spring miter clamps mostly. I found a set with suction cups that you put over the prongs, but I usually use the prongs and just clean up the surfaces after. They penetrate more in soft woods, as you would imagine. For most projects these are the fastest, easiest way to align a miter.

Will your tenons not align the joint?

[andy bessette]

I just use my parallel clamps, let the jaw extend past on one side of the joint, and use another parallel clamp at 90 degrees. You can adjust the tightness to flush the corners. Keep a rubber hammer handy. Put 2 clamps on the table, then the frame, then 2 clamps on top.

This is how I do it, using Pony or bar clamps. Simple. Use soft wood pads, if necessary, to prevent divots.

[George Bokros]

Will your tenons not align the joint?

I am thinking they should keep it aligned and a band clamp will pull it tight.

[Edwin Santos]

For picture frames and smaller boxes I use the clever Lee Valley clamp that Lee referenced. In fact, there was a recent entry in FWW on how to make such a clamp very inexpensively if you were so inclined.

For larger items that could benefit from a clamp with more strength, I am a big fan of the Merle clamp from MLCS. If you are installing tenons, the joint will self align. Even if you are not, I have found the MLCS clamp to pull the assembly into square although you could use some tape on the outside of the joint to assist with keeping it from sliding out of place while clamping.

[Bill McDermott]

George,

If your tenons are of the floating variety and are going in perpendicular to the miter faces, rather than parallel to the posts or rails, you will be in luck. I use Dominos that way sometimes. It makes it easy to clamp without things moving around.

Otherwise the suggestions above where you tighten and loosen clamps that oppose one another until everything is held in the proper position works fine. Ooops. Tightened it too much that way. Let me back off on that one a bit and tighten up the other side to push it where I want it... the dance.

[Paul Bent]

Rub blocks with hide glue is a quick, strong method. Knock off when done and clean up with warm water. Easy peazy.

[George Bokros]

George,

If your tenons are of the floating variety and are going in perpendicular to the miter faces, rather than parallel to the posts or rails, you will be in luck. I use Dominos that way sometimes. It makes it easy to clamp without things moving around.

Yes they will be loose (floating?) tenons and will be perpendicular to the 45* angle. You have confirmed what I was believing to be the case. Band clamps will work for me them. Thanks

[John Gornall]

I use stretch film around the frame and across the sides if necessary. No scratches - very gentle on the wood. The band clamp hasn't been used in years. I join a lot of frames.

[Dick Brown]

Masking tape and surgical tubing are my friend on 12 sided boxes

[Andrew J. Coholic]

I just use my parallel clamps, let the jaw extend past on one side of the joint, and use another parallel clamp at 90 degrees. You can adjust the tightness to flush the corners. Keep a rubber hammer handy. Put 2 clamps on the table, then the frame, then 2 clamps on top.

This is exactly what we do as well.