Superglue for mitered joints

[rdesigns]

I recently needed to glue the  mitered halves of ogee bracket feet. It's awkward not only because of their shape (no flat surfaces), but also because you have just the two pieces to try to clamp, instead of four.

I used a medium-set superglue from a (3 oz.?) bottle I got at Woodcraft. I did a trial using pieces of 1" Eastern White Pine.

The key to success is to lightly mist the mating surfaces with a water spray and then apply the glue to one of the surfaces. I used only hand pressure to press the halves together for about 30 seconds.

In about 2 minutes, I tried to break the joint apart (the sides were about 6" long and 4" wide, so I could exert a lot of force, both pulling and pushing the ends of the pieces. I could not break the joint.

With that successful trial, I glued all four sets of bracket feet in very short order. No clamps needed. Or nails. Or screws. Or Dominoes. Or lengthy clamping time. Just perfect, knife-edge, air-tight miters.

BTW, my Kapex did an admirable job of cutting glass-smooth perfect 45-degree miters prior to the glue up.

Maybe this has been told here before, but it was a real eye-opener to me.

 

[neth27]

The same as this http://www.tooled-up.com/product/evostik-rapid-mitre-fix-trade-351882/2533/?Referrer=googleproductlisting&gclid=CKbn06fA7LkCFQ1L3godb34Aiw  [big grin]
It's been used for years to fix mitres

John..

 

[John H]

FastCap has a pretty decent kit
http://www.fastcap.com/estore/pc/viewPrd.asp?idproduct=103&idcategory=48

or you can buy the products individually
http://www.fastcap.com/estore/pc/viewCategories.asp?idCategory=48

 

[junk731]

The only problem with Superglue and wood joints is that glue is very brittle and will not expand and contract with the wood. I our experience its not a long term glue and the joint will fail unless secured with an additional method.

John

 

[semenza]

There are some super glues with added rubber or other ingredients to make them somewhat flexible and have some give.

BSI (Bob Smith Industries) has a couple , and also some for use on foam.

Seth

 

[rdesigns]

The only problem with Superglue and wood joints is that glue is very brittle and will not expand and contract with the wood. I our experience its not a long term glue and the joint will fail unless secured with an additional method.

John

Since both halves of the miter joint are oriented the same with regard to grain, they should move together. Do you think it's still likely the joint will fail?

If so, I have the option of using a couple of glue blocks on the inside, hidden corners or the bracket feet.

 

[Michael Kellough]

The only problem with Superglue and wood joints is that glue is very brittle and will not expand and contract with the wood. I our experience its not a long term glue and the joint will fail unless secured with an additional method.

John

Since both halves of the miter joint are oriented the same with regard to grain, they should move together. Do you think it's still likely the joint will fail?

If so, I have the option of using a couple of glue blocks on the inside, hidden corners or the bracket feet.

A very small amount of glue can give the appearance of great strength and you never really know how much glue is needed until you've stressed a few similar joints to failure. Your mitered ogee bracket feet should be fine as far as shrinkage but I'd go ahead and add some discreet glue blocks to the back.

At first I thought this was a general question about flat miter joints so the following doesn't apply to the ogee bracket feet.

Yes, but failure is a matter of degree. If the only thing keeping the pieces of stock in place is the glue in the miter joint then failure will be complete. Most likely the stock is also fastened to something else so failure will be limited to a gap opening on the inside of the joint.

How much gap depends on grain orientation and how much bending force was used to close the joint initially.
Some guys bend the stock quite a bit instead of going back to the saw but if the molding is well nailed they can get away with it.

Flat-sawn stock will shrink across the stock not in line with the joint so as the stock shrinks the outside corners of the joint will remain tight and the inside corners will draw away from one another slightly. The wider the stock the larger the gap.

A glue block across the back of the joint will reduce the gap but in the case of flat molding it's seldom possible.

Quarter-sawn stock shrinks mostly in thickness rather than width so the joint will open significantly less.
Rift-sawn stock will be somewhere in-between.

 

[wascallyrabbit]

nexabond 2500 is supposed to be similar to super glue but has engineered flexability into it.  its pretty new so not sure how it holds up long term.