MDF

[krbass]

I am starting my tuba HT build this weekend and wondered if I can use MDF. I know it will make it uber heavy, but I have 4 1/2" 4'x8' sheets just lying in my dads barn waiting to be used. If MDF is a bad choice for any other reason then weight pls let me know and I will head over to the lumber yard for some birch ply, Just trying to save money any way I can.

[SeisTres]

I am starting my tuba HT build this weekend and wondered if I can use MDF. I know it will make it uber heavy, but I have 4 1/2" 4'x8' sheets just lying in my dads barn waiting to be used. If MDF is a bad choice for any other reason then weight pls let me know and I will head over to the lumber yard for some birch ply, Just trying to save money any way I can.

It actually can be used. But the reason almost no one here uses it is because it's heavier (as you pointed out), easily water damaged, and doesn't stand up to abuse as well as plywood. All those three things are major cons for pro sound cabs, but for home they really don't factor in.

So if you already have the sheets, that tips the scales right there. Just be careful is using screws as mdf is kind of delicate to them and also I hated the mdf dust. But of course, if you have four sheets of the stuff, I'm sure pretty familiar with that.

HOWEVER, if you're not going to be using tnuts, you might want to get some birch (or something with strength) for the driver spacer/baffle.

[Harley]

If MDF is a bad choice for any other reason then weight pls let me know and I will head over to the lumber yard for some birch ply, Just trying to save money any way I can.

You'll spend more in the long run in time and frustration using mdf and you'll moan for the rest of the cab's life about the weight. Give it a miss and get good ply.

[Gregory East]

If MDF is a bad choice for any other reason then weight pls let me know

Presumably the thing doesn't get moved twice a week. THT is gonna be one heavy mofo in MDF.

[gilscales]

I am starting my tuba HT build this weekend and wondered if I can use MDF. I know it will make it uber heavy, but I have 4 1/2" 4'x8' sheets just lying in my dads barn waiting to be used. If MDF is a bad choice for any other reason then weight pls let me know and I will head over to the lumber yard for some birch ply, Just trying to save money any way I can.

1/2" MDF is a bad choice as it will flex to much under the internal pressures of the cabinet, do not waste your time with MDF get some 12mm BB in 5' x 5' panels for abot $20 to $25 ea.

If you just happen to be local to me then I can hook you up with some 12mm BB for my cost at $20 a sheet (that price is with sales tax)

[bzb]

I just picked up a sheet yesterday - my price went up to $26!

MDF should be OK for a THT... assuming it's actually being used for that.

[Mikey]

With all of the time, effort, and money that goes into a build, I think it would be foolish to use MDF. You're just asking for problems and headaches. Even cheap grades of "acceptable" plywood has it's pitfalls. If you want the woodworking to go as smoothly as possible and the cab to be of the best quality possible, use BB. Yeah, it'll cost you, but it's SO well worth it. IMO, the wood is a bad place to skimp.

[coolhandjjl]

MDF is best installed and left unmoved. Doors built with MDF have to have a thick oak strip inlaid along the hinge side for strength.

[Zack Brock]

MDF cuts nice and works good for butt joints with glue. As far as I know, it won't impede or affect the sound in any way so if you've got it, use it. Weight is pretty much the only issue.

gilscales mentioned that 1/2" MDF might flex too much - if that is an issue you could put in some extra bracing to keep the flex down to a minimum.

[Harley]

MDF cuts nice and works good for butt joints with glue.
Weight is pretty much the only issue..

Sorry, but I have found mdf is not good for butt joints, and neither is it good when you want to screw a panel into another that is end on - it splits out.

That's why the furniture trade has special fittings for joining mdf panels, and speed has been a byproduct.

Mdf is not moisture resistant and in high humidities or damp places it can easily swell.

[gilscales]

MDF cuts nice and works good for butt joints with glue.
Weight is pretty much the only issue..

Sorry, but I have found mdf is not good for butt joints, and neither is it good when you want to screw a panel into another that is end on - it splits out.

That's why the furniture trade has special fittings for joining mdf panels, and speed has been a byproduct.

Mdf is not moisture resistant and in high humidities or damp places it can easily swell.

MDF will swell with high humidity beacuse is it pressed from wood fibers and resin and the end grain will absorb moisture like a sponge as the center of the panel is not as dense as the outer edges though with time even the face of the material will absorb moisture from the air, this less dense center of the panel is another reason the screw holding ability is weakened

Read this article and I can vouch for the irritating sawdust to inhale as I have worked with MDF for over 25 years, even some people find the sawdust bothersome to their skin!
http://www.design-technology.org/mdf.htm

[bzb]

MDF cuts nice and works good for butt joints with glue.
Weight is pretty much the only issue..

Sorry, but I have found mdf is not good for butt joints, and neither is it good when you want to screw a panel into another that is end on - it splits out.

That's why the furniture trade has special fittings for joining mdf panels, and speed has been a byproduct.

Mdf is not moisture resistant and in high humidities or damp places it can easily swell.

MDF will swell with high humidity beacuse is it pressed from wood fibers and resin and the end grain will absorb moisture like a sponge as the center of the panel is not as dense as the outer edges though with time even the face of the material will absorb moisture from the air, this less dense center of the panel is another reason the screw holding ability is weakened

Read this article and I can vouch for the irritating sawdust to inhale as I have worked with MDF for over 25 years, even some people find the sawdust bothersome to their skin!
http://www.design-technology.org/mdf.htm

The MDF I've gotten for the last few years feels like it has some sort of coating on the faces. It's incredibly smooth, almost polished feeling. It doesn't seem to take up moisture as badly as it used to (or anywhere near as bad as particle board does).

When I used to build cases and car sub boxes out of 3/4" MDF, I brushed thinned out, regular old woodworkers glue on the end grain to "seal" it of sorts. That seems to keep it from wicking up moisture as quickly, as well as paint - it's a trick I learned from a painter.

MDF has plenty of good uses, even if it's expensive as good quality plywood now... I still use MDF now for things like benchtops that will have a covering. Heavy and absolutely flat. Leftover scraps usually become jigs, story sticks, or replaceable shelving for the shed. But you're right - it doesn't hold screws well at all, and shear strength is terrible. I always have MDF dadoed/rabbeted for additional mechanical joint as well as extra glue joint.

As far as the skin irritation goes - I can attest to that. Of course, from just mosquito bites, I swell up like I need an epi pen.