How to assemble mdf?

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I second that. I built a set of cabs from MDF...then decided to do the cabs out of ply. After removing the drivers from the MDF...I picked up the cab and SMASHED it onto the concrete outside to do an "impact" test. Those E'fers broke everywhere else first before the butt joints were damaged. I just simply used carpenters glue and had clamped the panels together during construction.

I completely agree with you.
I've done the same as you too, same construction and destruction. Throwing them up in the air as high as I could and watching them bounce. Darn things wouldn't come apart. I found it was far simpler to just run them through the table saw, cut them into pieces!
 
No quotas only files size limits (test attachment). Sometimes image upload gets balky, i just keep stabbing the upload button till it goes.

Don't know...

It's baffling me. . . .
It lets me select and upload pics as usual, but then the "Manage Attachment" window comes back blank! No error or warning messages or file size complaint, just blank, stuck, doing nothing, going nowhere.
Weird.
 
Building with MDF

I have had great success with a furniture gun firing 1.5 and 3.0 inch straight brads into pre-glued joints (not u-brads but straight wire nails). They have no heads to break the surface, they bury themselves 1/8 deep and as long as you fire them straight I've never had a problem. Glue the cabs, clamp them and fire brads every 1/2 inch and leave them clamped then for a day or two. The cabs wind up strong as hell and have never split or buzzed.

MDF is a bummer because it sucks water like a sponge but sealing them first with multiple coats of sanding sealer, sanding between coats, works nice.

[edit] They take finish nicely too if you sand carefully each time after the sanding sealer is *well* dry. That is, between coats and a final after you're done...

Regards,
Tom
 
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I hate screws in MDF

I've found that screws in MDF weaken the material and have a tendency to pull out and make a mess. MDF isn't stable under that kind of load. It is essentially glued powder and has no real strength like wood. The brads don't stress the structure of the MDF like screws do under differential loads, instead they produce a friction load that keeps the glued joints from moving instead of trying to hold two pieces together with force like screws.

Regards,
Tom
 
I have had great success with a furniture gun firing 1.5 and 3.0 inch straight brads into pre-glued joints (not u-brads but straight wire nails). They have no heads to break the surface, they bury themselves 1/8 deep and as long as you fire them straight I've never had a problem. Glue the cabs, clamp them and fire brads every 1/2 inch and leave them clamped then for a day or two. The cabs wind up strong as hell and have never split or buzzed.

MDF is a bummer because it sucks water like a sponge but sealing them first with multiple coats of sanding sealer, sanding between coats, works nice.

[edit] They take finish nicely too if you sand carefully each time after the sanding sealer is *well* dry. That is, between coats and a final after you're done...

Regards,
Tom

What is your preferred sanding sealer for MDF? I have some MDF enclosures that need more sealing.

I like using a nail gun, comes in handy when attaching moldings and casings and such.

I built some display boxes out of pine and quite a lot of my nails ended up piercing out through the sides!
 

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I was thinking of using interior bracing, and screwing Into the mdf from the inside.

Take that a step further and eliminate the screws, they are slow and unnecessary. Use brad nails and full length cleats. The first time I did a box like this I thought what in the **** have I been doing it any other way for? A huge lightbulb came on.
 

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I respectfully disagree...Fine Woodworking did extensive destructive testing of a wide range of joint constructions a good number of years ago (Testing Joints to the Breaking Point by Bruce Grey FWW #148).
Unless you're dropping your speaker cabinets off of 20' rooftops or having your 320 pound brother-in-law use them as chairs, I can't imagine that screws and glue wouldn't be plenty strong for a speaker cabinet's intended use.

See also aptquark's post:

I second that. I built a set of cabs from MDF...then decided to do the cabs out of ply. After removing the drivers from the MDF...I picked up the cab and SMASHED it onto the concrete outside to do an "impact" test. Those E'fers broke everywhere else first before the butt joints were damaged. I just simply used carpenters glue and had clamped the panels together during construction.

And AEIOU's post:

I completely agree with you.
I've done the same as you too, same construction and destruction. Throwing them up in the air as high as I could and watching them bounce. Darn things wouldn't come apart. I found it was far simpler to just run them through the table saw, cut them into pieces!
 
AEIOU

To tell you the truth I just grabbed a generic sealer from the Home Depot, it was a thin water-based sealer that I applied in thin coats, sanding in between. I found the water-based sealers, applied very sparingly because MDF eats water, worked very well. It might have been Enduro, but I have used several. The urethane ones seemed to get gummy and were a pain...

Regards,
Tom
 
Take that a step further and eliminate the screws, they are slow and unnecessary. Use brad nails and full length cleats. The first time I did a box like this I thought what in the **** have I been doing it any other way for? A huge lightbulb came on.

I've found that everyone seems to have their own way of doing it, that is they eventually find/develop a comfortable and repeatable technique.

I like using rabbets on plywood, that way the end grain gets covered up, is less visible. You can get an idea from the way I made these enclosures. I had wanted to make them entirely of plywood, but I didn't have enough scrap material, so only the sides and top are plywood/wood grain. No nails or screws, just Gorilla Glue and clamps.
 

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Yes I guess I was speaking of my style as I really only make test type boxes that can be finished later or sometimes starting again so I was really thinking about time conservation. I really like to be able to continue the project right after gluing as I am rather impatient and doing it with Brad nails on the inside means no exterior fastener holes to fill except the back panel. Go for lunch, come back and pop in the drivers 🙂
 
I made this cabinet 1990 (although not MDF) using lots of carpenters glue and individualy countersunk wood screws every 4" to 6".

It has been dragged ,rolled and knocked over and been through 4 moves and seen many shows with a large stack of amplifiers on top of it.

I never once had an issue with the butted seams coming apart.

One time I had to get inside of it for a modification and had to take out the driver to do it.
Otherwise I would have destroyed it trying to get one of the end caps off. jer


P.S pics were taken with a 10.1 mega pixel camera ,resized and posted in less than 5 minutes using a free program called "IrFranview", cheers!
 

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don't invent excuses.
Learn how to post pics that show what needs to be seen.

Nothing needs to be seen, however a picture is worth a thousand words.
If you don't like my pictures don't look at them.
As far as my pictures being too large or whatever, they look fine to me on my screen. But if it doesn't agree with you, or some how bothers you, please report it to the Moderators instead of being rude to me.
 
Nothing needs to be seen, however a picture is worth a thousand words.
If you don't like my pictures don't look at them.
As far as my pictures being too large or whatever, they look fine to me on my screen. But if it doesn't agree with you, or some how bothers you, please report it to the Moderators instead of being rude to me.

HERE IS WHAT i DO, I open the pic in MS Paint...and then resize the pic with % increments. Look for the tab or option to resize...simple.
 
I made this cabinet 1990 (although not MDF) using lots of carpenters glue and individualy countersunk wood screws every 4" to 6".
I feel for you. That's how I used to do it too.

I never once had an issue with the butted seams coming apart.
Butt joints are not really the issue. The glue, if used properly will work just as well and the screws become redundant. Tacking with Brad nails allows you to continue and eliminate waiting for the glue to dry. No screw holes to fill. If you have done this a number of times, you will understand.


P.S pics were taken with a 10.1 mega pixel camera ,resized and posted in less than 5 minutes using a free program called "IrFranview", cheers!
Oh man, I feel for you again. On a mac, in iPhoto, you simply click on export and up comes a screen requesting input on the size and type of file you wish the final product to be. 5 minutes sounds terribly labourious. Maybe you meant 5 seconds? 🙂

As far as my pictures being too large or whatever, they look fine to me on my screen.

You are missing the point. Keep in mind that not all of us share the wonder that is high speed. I am guessing you have no idea how frustrating it is to wait when you don't have that advantage. We ask that you show courtesy and minimize the size of your files. Disregard for this leads to contempt. I believe this is what you are experiencing now.

Here is a 2MB shot reduced to 111k with a couple clicks. Do you need more than that?
 

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