Finger Joint help

[LowellH]

Hi,

I'm building a pine cabinet for my 5E3, and encountered a problem this weekend - with glue in the joints, I couldn't get the boards to fit together. The dry fit seemed perfect - snug but not too tight. With a little tite-bond II glue (supposedly slow-setting) in the joints, I couldn't for the life of me get them to seat. Finally, I took the two boards apart and cleaned off the glue.

Are there any tricks for this, like a low-viscosity glue or something? Should the joints be snug before gluing? I've never made finger joints before. Can someone help me out?

Thanks for your help.

[Tom Phillips]

I have seen this issue discussed in woodworking articles.
Titebond II is 48% solids and the “Open assembly time” is specified at only 5 minutes. The moisture in the glue also makes the wood swell a little. All this adds up to cause the problem you are having. IMHO it sounds like you need to allow more dry fit room in joints.

How you correct this is another issue. I assume that, if you use a jig with matching router bits, the tolerance is taken care of. Otherwise, I guess it takes experience to get it right which you are now acquiring. Hopefully, someone will be able to provide some accepted guidelines.

Regards,
Tom

[LowellH]

Thanks for the reply Tom. I didn't use a router, but that is a good idea. It never occured to me, and it probably would have made cleaner cuts. We used a 3/8" dado blade (actually it measured a few thousandths over 3/8"), and made a finger joint jig.

Here's a picture of the jig:


Here's a picture of some corners we mocked up with the same glue. No problems - but they're a lot smaller.


I figured I might just need to sand the joints down a small bit.

Any other suggestions?

Thanks.

[Tom Phillips]

Your mock up joints look really good. I don't have any specific suggestions but if I was doing it I'd try to adjust to give a little looser dry fit and experiment with some mockups of the full width of boards that you will be joining.
Regards,
Tom

[John_H]

Are there any tricks for this, like a low-viscosity glue or something? Should the joints be snug before gluing?

Where I come from that's called a box joint. Your joints should fit together freely before gluing, and clamping. There needs to be room for the adhesive. Titebond II is great glue, but probably not the best choice for your application. It's pretty thick right out of the bottle. That's fine for a small glue joint where you don't want it to run, but difficult when you're working on something large. Waterproof glue isn't needed. I'd use Titebond Original thinned a little, and applied with a small paintbrush so you can work fast. A couple pieces of paper as shims in your dado pack is probably all you need. G/L

[R.G.]

Do a google for "Lynn's Jig", possibly tossing in "finger joint". This thing is best I've ever seen for finger joint making. It lets you selectably make the joints tighter or looser, and any size you like. It naturally thinks in 1/16 inch increments, so making Imperial sized joints is a breeze. You could turn it into a naturally-metric unit by changing out the leadscrew and two nuts.

[John_H]

What is the best way to thin it?

Thin it with water. It doesn't take much. Stirred, not shaken.