MDF for braces?

[bjpell]

I'm making a THT and wondered if I could make all of the needed internal braces and the speaker spacer out of MDF

[Harley]

You can but why would you want to do that? MDF is much heavier and it doesn't take too kindly to screws being drilled into the edges. Certainly not my material of choice.

Just use ply.

[Grant Bunter]

You can but why would you want to do that? MDF is much heavier and it doesn't take too kindly to screws being drilled into the edges. Certainly not my material of choice.

Just use ply.

+1

[bjpell]

You can but why would you want to do that? MDF is much heavier and it doesn't take too kindly to screws being drilled into the edges. Certainly not my material of choice.

Just use ply.

why? well, because it appears that cultist is showing that I will not have enough Baltic Birch Ply for everything with 3 sheets. It was special order and at 75 a sheet no way I'm ordering more if I can use something else. I do otoh have 1/2" MDF. The way I look at it, is that the weight doesn't matter with a THT, its a huge paper weight sitting in the coroner anyway. It's not like I'm going to be moving it around after its set in the living room. Do ya have any other suggestions? If I dont use MDF what other wood at Lowes would you suggest for the spacers?

[Bruce Weldy]

Two things....

1. use the MDF based on your situation....or any scrap ply you have hanging around.

2. find a better place to buy BB. It's less than $30 for a 5x5 down here.

[dswpro]

While it is generally void free, MDF falls apart much faster when being moved around. If it ever gets wet, it literally crumbles as it expands absorbing moisture like a sponge. It is basically sawdust and glue. It doesn't hold nails or brads particularly well, or fine pitch screws. If you are building a sub, think about the low frequency vibrations you will be subjecting the wood to. I would rather use OSB (oriented strand board) than MDF. Keep the MDF for your shop and closet shelves where you can hope they stay dry and vibration free.

From the wikipedia on MDF:
Drawbacks of MDF:
Denser than plywood or chipboard (the resins are heavy)
Low grade MDF may swell and break when saturated with water.
May warp or expand if not sealed.
Contains urea-formaldehyde which is a probable carcinogen and may cause allergy, eye and lung irritation when cutting and sanding
Dulls blades more quickly than many woods
Screwing into the edge of a board will generally cause it to split in a fashion similar to delaminating.
Subject to significant shrinkage in low humidity environments.
Painting with latex paints is difficult due to rapid water absorption.
Most finishes appear uneven and nail holes tend to pucker.

[Bruce Weldy]

It's braces for a HT sub......it'll be ok if that's all he has. As long as it's glued in good with PL - it's not going anywhere.

[Bill Fitzmaurice]

I will not have enough Baltic Birch Ply for everything with 3 sheets. It was special order and at 75 a sheet

I'm afraid you got screwed on that, and not in the good way. Real lumberyards have BB in stock. The one you went to probably drove across town to a real lumberyard to get the BB, then sold it to you at twice what they paid for it.

[bjpell]

I appreciate your responses. I guess i'll look for another supplier here in Podunk Central Pennsylvania and just buy another sheet. It took a week to get the 3 I ordered and they all came damaged on the edges where it looked like all three were dropped on an edge while loading it, so I had more waste than expected working around the bashed-in / split corners.

[Stratispho]

What about using another grade of ply just for the braces instead of MDF?

[jswingchun]

What about using another grade of ply just for the braces instead of MDF?

That will work since you are only gluing edges on the braces, not to the face of the ply.

[bjpell]

I had the opportunity to go to Lowes finally today. I found this and I'm wondering if I should I bite the bullet and buy this for making spacers:
http://www.lowes.com/pd_12227-99899-NA_ ... 856&rpp=32
It appeared to have 4 equal ply's, and free of voids from the edges I saw. I really want to use my 0.5 inch MDF I have here already, but from previous responses I get the feeling that I should only use it if its the only option I have.

[koturban]

I had the opportunity to go to Lowes finally today. I found this and I'm wondering if I should I bite the bullet and buy this for making spacers:
http://www.lowes.com/pd_12227-99899-NA_ ... 856&rpp=32
It appeared to have 4 equal ply's, and free of voids from the edges I saw. I really want to use my 0.5 inch MDF I have here already, but from previous responses I get the feeling that I should only use it if its the only option I have.

Have you asked them if they have partial sheets of 1/2" ply laying around? You might get a deal.

You don't need a lot of wood for the braces.