strongest joints for box making

[Bruce]

Re: strongest joints for box making

A simple rabet joint will work well with MDF or plywood. Modern glues (e.g. Titebond) are really, really good. -- Doug

I too use rabbet joints extensively for a number of good reasons:
1. An advantage over but(t) joints is that there's no slipping or sliding of pieces because you can clamp along two planes.
2. The inside measurement of the enclosure between the rabbet joint at the top and bottom allows precise assembly of parts resulting in perfect vertical and horizontal spacing.
Here's a layout of Modula MT components prior to gluing and clamping.
(The port has previously been glued onto the interior brace & the lines on the inside of side pieces are to help position braces during glue-up):

(Note: the baffle won't be glued on at this time)
3. Corner joints are exceptionally strong because the parts are glued along two planes.
4. During assembly it's easy to focus on squaring up the corners by simply using bar clamps across the diagonals.
In fact, with rabbets, I found it possible (and easier) to assemble and glue the whole enclosure (sans baffle) in one step ;)
like here:

5. They're very easy to make using a table saw or router.
6. Finally, there's no need to use screws - ever.:D
HTH,
Bruce

[dwigle]

Re: strongest joints for box making

Geez Bruce, I have clamp envy.

[Jason]

Re: strongest joints for box making

I wonder if some of the more elaborate joint types (dovetail, box/finger, etc) are actually less strong than regular old but† or rabet type joints if you are using MDF. It's been shown that the glue is actually stronger than the wood, and MDF is considerably less strong than just about any solid wood. So while you may be getting more glue surface, you may be reducing the MDF's structural integrity at the joint. I think as long as you keep the dovetails or box joints spaced appropriately they would be adequately strong, but I can easily envision some scenarios where they could be very fragile.

That said I normally do rabet joints like Bruce. I've never had a joint failure with that or even old crappy but†joints (I built a sub box in college and the edges were all cut with a junky old jig saw). As long as you put enough glue in the joint it will hold itself together! My personal opinion is that unless you are using solid wood and you'll actually see the "fancy" joints, it's probably going to be more work than it's worth and won't really give you an appreciably stronger box.

[badman]

Re: strongest joints for box making

I wonder if some of the more elaborate joint types (dovetail, box/finger, etc) are actually less strong than regular old but† or rabet type joints if you are using MDF. It's been shown that the glue is actually stronger than the wood, and MDF is considerably less strong than just about any solid wood. So while you may be getting more glue surface, you may be reducing the MDF's structural integrity at the joint. I think as long as you keep the dovetails or box joints spaced appropriately they would be adequately strong, but I can easily envision some scenarios where they could be very fragile.

That said I normally do rabet joints like Bruce. I've never had a joint failure with that or even old crappy but†joints (I built a sub box in college and the edges were all cut with a junky old jig saw). As long as you put enough glue in the joint it will hold itself together! My personal opinion is that unless you are using solid wood and you'll actually see the "fancy" joints, it's probably going to be more work than it's worth and won't really give you an appreciably stronger box.

Mostly true. The rabbets definitely help in aligning. Done right, they also can allow you to use the veneer on ply as your only finish. You rabbet one piece the width of the material, and leave 1/8" or so of thickness. Then you only have a 1/8" exposed edge.

[ktaillon]

Re: strongest joints for box making

Spline joints work well and are easy to do. If you look hard you can see the spline at the joints..

[Knowsknone]

Re: strongest joints for box making

Ive always used ****-joints. Just for some extra strength, coat some finishing nails in loc-tite and hammer em in, then take a nail punch and get them below the surface, take and wood friendly filler cover, paint/vinyl ect.

My center channel is done this way, although its 3/4 mdf with 45 degree **** joints, I have sat on it while it was vertical and it didnt even complain..
Im about 190lbs soo even with just glue and a few finishing nails they can hold up. I cant guarantee it will always hold up, but mine did lol.

Also another way is to drill holes, and stick dowels in them with some wood glue or better, works well and is very strong.

[dryseals]

Re: strongest joints for box making

This is my favorite bit for square corners. I use a shaper but have used the router version too.