Joint construction

[stevem]

I've always made enclosures out of MDF and used but joints with wood glue and sheet rock screws. Is there a better way? I'm considering using tongue and groove joints, but should I stay with screws? Has anyone used pneumatic nail guns, either brads or finish nails? This is really easy, but I wonder if it won't hold well. Any thoughts or experiences?

[Joe Alesi]

Hello Steve

Recently I purchased a mitrelok bit in order to make seamless corners for boxes.



He are some links:
http://stusshed.wordpress.com/2008/09/06/carb-i-tool-mitre-lock-bit/

http://www.timbecon.com.au/details/l...its-11515.aspx



Knowing me it will be many moons before I get around to trying it though.

Best
JA

[grumpy]

Those work great, if a bit fussy to set up. Worth putting a sled/jig together
for the panels that have to be run vertically (hard to keep a straight/true edge,
otherwise). Having a router table (or shaper) is really helpful.

Simpler dado/rabbet combination works well too, and can be done on a
tablesaw.

[SMKSoundPro]

Here's the joint that JBL shows in there SR brochure. I have used it many times. Pretty foolproof. I have a Unisaw and a Jesada stacked and packed dado set.

[Ducatista47]

I built a pair of cabinets using the method set out so clearly by Macaroonie in this thread: http://audioheritage.org/vbulletin/s...ad.php?t=17238 It does look something like the method in SMK's post above. I used MDF and went with 50/50 dimensions for the grove/lands, and employed a screw on back, it is very adaptable.

As a result I have some of the most solid cabinets ever built for the speaker design I made from plans. I went with a double thickness front baffle (thanks to Ian for that great suggestion) and no rocket science was required to figure out the new dimensions, just addition and subtraction. Whenever I was particularly stumped by the exact configuration of a panel, I just drew a few sketches and it popped right out. The top and bottom pieces go in like a jigsaw puzzle and are a thing of beauty. It is almost a shame they have to be glued up and hidden.

I can take none of the credit but I enjoy all of the rewards. I was new to routers, but it was really easy. Just buy or borrow a lot of clamps if you have 48 inch seams like I did!

Highly, highly recommended. Thanks, Macaroonie.

Clark

[Mr. Widget]

Has anyone used pneumatic nail guns, either brads or finish nails? This is really easy, but I wonder if it won't hold well. Any thoughts or experiences?

All of my "utility" enclosures are butt jointed using a Senco SKS narrow crown staple gun... the staples will not pull out without a hell of a fight so put them where you want 'em.

The method I like for strong mitered joints only requires a table saw and a blade that cuts an 1/8" kerf. You cut a standard miter, flip the board over to the opposite side of the blade and lower the blade then cut a slot... then you slip a narrow strip of masonite in the slot and glue up your joint... super easy and very strong.


Widget

[macaroonie]

Its good to know that you got a leg up with my method. Mac

[stevem]

Did you just use wood glue and clamps? Did you use screws?

\

I built a pair of cabinets using the method set out so clearly by Macaroonie in this thread: http://audioheritage.org/vbulletin/s...ad.php?t=17238 It does look something like the method in SMK's post above. I used MDF and went with 50/50 dimensions for the grove/lands, and employed a screw on back, it is very adaptable.

As a result I have some of the most solid cabinets ever built for the speaker design I made from plans. I went with a double thickness front baffle (thanks to Ian for that great suggestion) and no rocket science was required to figure out the new dimensions, just addition and subtraction. Whenever I was particularly stumped by the exact configuration of a panel, I just drew a few sketches and it popped right out. The top and bottom pieces go in like a jigsaw puzzle and are a thing of beauty. It is almost a shame they have to be glued up and hidden.

I can take none of the credit but I enjoy all of the rewards. I was new to routers, but it was really easy. Just buy or borrow a lot of clamps if you have 48 inch seams like I did!

Highly, highly recommended. Thanks, Macaroonie.

Clark

[stevem]

I have a narrow crown staple gun as well as a brad nailer. Those staples really are hard to get out. Do you glue and clamp first, and then staple? When I use screws, they pull the joint together like a clamp, but I don't think the staples would. It really would be a lot easier to use staples instead of screws, but usually with things like this there is no free lunch.

I've always heard that a wood glue only joint is as strong as the wood itself, and I think using lumber or plywood is probably fine with just glue. I really wonder about MDF because its not fibrous, and the glued area will rip right off when stressed. Any thoughts?

All of my "utility" enclosures are butt jointed using a Senco SKS narrow crown staple gun... the staples will not pull out without a hell of a fight so put them where you want 'em.

The method I like for strong mitered joints only requires a table saw and a blade that cuts an 1/8" kerf. You cut a standard miter, flip the board over to the opposite side of the blade and lower the blade then cut a slot... then you slip a narrow strip of masonite in the slot and glue up your joint... super easy and very strong.


Widget

[Allanvh5150]

MDF will rip when stressed. The cabinet material is very dependent on what you will be doing with the cabinets. If they will be moved around a lot you should use plywood. MDF is a good cabinet material because of it's density. It is reasonably resiliant to handling. Chipboard is also very good and it is my prefered product if the cabinet will be built in. I always, unless they will be visible, screw and glue my boxes. If you are using a nail gun you can put 2 nails in the hold in place and then put your clamps on, then finish the joint with tha nail gun. You woant have a problem with the joint not pulling up.

Allan.

P.S. JBL have used MDF, chipboard, plywood and probably solid timber. Each has its own merrit.

[macaroonie]

Did you just use wood glue and clamps? Did you use screws?

\

Both but I was post veneering. Very few screws are needed , just enough to hold it all together until the adhesive sets . If you wade through the thread you will see a pic of the box assembled with no glue or anything and it is solid as is. Nice simple DIY method but strong also.

Oh I do not use MDF for anything anymore !! In spite of its workability it has more downsides than up plus the dust is plain nasty. I would rather pay the extra and not suffer the grief of MDF. IMHO

[Ducatista47]

Did you just use wood glue and clamps? Did you use screws?

I used screws to put even pressure on the two 3/4 inch panels I glued together to form the double thickness front baffle. I didn't have the necessary bench and weights to do it the old fashioned way, just clamping the edges instead. I also screwed & glued the wood cleats for the removable back. On the regular joints, no. In other words, I used screws to clamp, not to fasten. They would not have added anything to the joinery. Any screw going through the end (edge) of plywood or MDF is nearly worthless anyway. Gluing dowels or Widget's pieces makes a lot more sense there. With Macaroonie's joinery the entire joint is self-dowled.

About those joints:

I've always heard that a wood glue only joint is as strong as the wood itself, and I think using lumber or plywood is probably fine with just glue. I really wonder about MDF because its not fibrous, and the glued area will rip right off when stressed. Any thoughts?

I used MDF for this project for its superior sonic properties. Macaroonie's joinery makes a rugged mechanical "fastener" of the rabbets before they are glued, so the box is more like a solid piece of MDF than a bunch of panels. I did not have to compromise the sound for the convenience of plywood. That is the beauty of it. It is so true and tight, and you will see that it must go together in one particular order. It really does lock up like a puzzle box, so when it is glued it is as stiff as a seamless piece. At least the way I used it, these boxes hold together without glue when you dry run the assembly. No panels can fall over or out. It is quite remarkable. When you put the top on nothing can move, even with no back in place.

Most remarkably, if you thump the top with your fist nothing rattles - with nothing glued and one side missing!

Clark

[Mr. Widget]

I have a narrow crown staple gun as well as a brad nailer. Those staples really are hard to get out. Do you glue and clamp first, and then staple? When I use screws, they pull the joint together like a clamp, but I don't think the staples would. It really would be a lot easier to use staples instead of screws, but usually with things like this there is no free lunch.?

Depends on the geometry and the fit up. With warp free stock that is well cut I can simply lean on the stapler and the joint is tight... if there is a warp in the wood or some other reason that the pieces don't want to fit snugly with minimal pressure, I break out the clamps... I have dozens and dozens. (Don't buy wood from Home Depot... it is terrible crap that is typically warped and very poor quality.)

I've always heard that a wood glue only joint is as strong as the wood itself, and I think using lumber or plywood is probably fine with just glue. I really wonder about MDF because its not fibrous, and the glued area will rip right off when stressed. Any thoughts?

If you have structurally sound wood that fits well, a simple glue joint can be surprisingly strong... however chip board, particle board and MDF are not very structurally sound except in compression.

Oh I do not use MDF for anything anymore !! In spite of its workability it has more downsides than up plus the dust is plain nasty. I would rather pay the extra and not suffer the grief of MDF. IMHO

I hate it too, but I haven't found an affordable alternative to MDF wrapped in birch plywood...


Widget

[DavidF]

I've always made enclosures out of MDF and used but joints with wood glue and sheet rock screws. Is there a better way? I'm considering using tongue and groove joints, but should I stay with screws? Has anyone used pneumatic nail guns, either brads or finish nails? This is really easy, but I wonder if it won't hold well. Any thoughts or experiences?

Screws and butt joints can really expedite your project. Saves a lot of extra cuts and alignments. But it really takes some precision cuts to get a good tight fit on the pieces.

I only use "buried" screws as a clamp alternative and then pull them out of the finished project. Just do not like the thought of leaving them in the work in case they loosen and rattle around.

A good and tight joint held by glue is very strong and durable. The more wood-to-wood glued surfaces you can lock together the better (butt joints provide minimumal contact of course). I have used simple rabbets without problem. They offer a good compromise of time/effort, make up for minor slop in the joints, minimize air leak potential and provide a good long lasting joint. I will take extra steps for the baffle and use dados to lock in the side pieces to the baffle.

I too have used Widget's method he described above but only on smaller projects. You (well, I for certain) need precision tools to help get those nice fitting mitre joints. I do have such tools but if you have them this works very well and you can move along fairly quickly.

[UreiCollector]

I like to use biscuits, glue, and air nails. A smear of liquid nails on all internal joints ensures air tight seal.

The biscuits really help to align the joints, and the air nails leave small holes that can easily be filled and sanded. This is now my preferred method.