lock miter glue ups

[jim sauterer]

i normally glue both sides on glue ups.my question is the lock miter joints i am gluing are tight when they are just fitted together. when i glue both sides i end up with gaps along the out side miter.because of the large surface area with this joint would it be strong enough with just gluing one side of each joint.any input appreciated.

[Mark Rakestraw]

Hi Jim,

I've started putting a small bead of glue on the outside edge of one piece (about where the 45 degree surface meets the lock finger) and another bead in the groove of the other piece. I then clamp them together without bothering to spread it out. A bit of experimentation with the size of the beads, it's pretty small, and you can get minimal squeeze-out and it's fast. My joints do seem to come out tighter now that I've given up on spreading the glue onto both pieces. Given the mechanical locking of the joint and the surface area I don't think there's much danger of failure if coverage isn't 100%.

[Lee Schierer]

The joints are still basically end grain joints, which tend to soak up more glue than face grain. You need to apply enough glue so that both surfaces are wetted for proper joint strength. This can be done by applying glue to one side only and then assembling the joint. Excess squeeze out would indicate you used too much glue. Applying thin layers to both sides will result in a time delay which will allow the glue on one side to start drying before the joint is assembled which could be creating your gaps.

However, your gaps may also be due to out of square joints. If your fence is not perfectly 90 degrees to the table you may not be getting 45 degree cuts on each half of the parts. Check your set up carefully to insure you are at a true 90 degree angle on the vertical cuts.

[Mark Rakestraw]

Hello Lee,

Hmmm, I guess it would be end grain joints if you used the lock miter as a drawer lock bit to make a box...hadn't thought of that. I use the lock miter bit to join a face frame stiles with an end panel stiles, so it's still a face grain joint.

good catch about checking the fence for square.

[Larry Edgerton]

I have found that too much glue makes it hard to pull the joint together. I thin the glue out a bit and apply it in one side with a brush, and the other side I spritz with a water bottle so I have time to get it clamped well.

Lee, you must be thinking of that drawer joint, can't remember the name?

[Anthony Whitesell]

Lee and Larry, you're both right. I just got finished using both bits (lock miter and drawer lock) and in both of my cases (and I suspect in most cases) the cuts were made in the end grain.

As you can see in a similar thread I started. I had problems with gluing both joints together. I suspect the loss of moisture from the glue being a year old and almost empty in conjunction with the end grainmade it terribly difficult (actually impossible) to adject the pieces once they touched. The glue dried only slightly slower then typical CA super glue.

On the OP originial topic. I have been only applying glue to one side of the joint. If the joint if really good, most of the glue will end up squeezed out, IMNO (in my novice opinion). I'm going to try dampening both sides and then applying the glue on my next glue-up, although the next glue-up is not end grain not lock miter or drawer lock joint.