MDF, GLUE and nails

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Project Subwoofer for 15 inch driver

Tools. Jigsaw, hand saw, straight edges and 90 degree rulers

steps

  1. Cut the 4 outer panels.
  2. cut the top and bottom + extra baffle for rebatted driver installation
  3. drill holes using jigsaw for plate amp and driver
  4. Glue 2 baffles together, i can put weights here
  5. pre-drill holes for nails or screws for outer panel
  6. assemble 4 outer panels and bottom cover with PVA glue and screws
  7. cut braces
  8. install brace Do i still need to nails/screw the braces ?
  9. Install top cover with pva glue


questions

  1. what kind of nails or screw do i need ?
  2. how long should they be ? Diameter ?
  3. if the lenght of one side is 18 inches , how many nails/screws would this require ?
  4. Would i just need a couple of nails to hold the panels while the glue dries ?
sounds good ?
 
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I use an 18 gauge nail gun. These nails are coated with a glue. The heat from friction when fired into the wood melts the glue so the nails slide in, then re-hardens making a very tight bond.

When I nail wood it is to act like a clamp until the glue dries. I put in enough nails to make the wood bind tight together and squeeze out any residual glue.

Screws into MDF do not bite well. You can cross drill a larger hole in the MDF, then glue in a hard wood dowel peg into the wood, then drill the hole for the screw. This works much better and both ends of the dowel can be sanded flush with the MDF.

Be sure to wear a mask when cutting MDF. The dust is not good for you.

Another thought is to use a hardwood in all the interior corners as a brace between connection MDF boards. I use 1 X 2 or smaller with copious amounts of glue.

Many people use large clamps to assemble their cabinets. If you can borrow clamps it is a very good idea.
 
I use inside cleats and install them on one panel first. Then I glue and clamp and fire the Brad nails on the inside, release the clamps and go onto the next panel. Super fast, easy, very strong, self aligning and no exposed fasteners.

Use plywood.

Get a circular saw and a straight edge or sawboard you can clamp in place for cutting. Nice cuts, relatively inexpensive and easier than a table saw which can be somewhat tricky if your experience is limited, not to mention expensive.

Cheers
 
I think those screw in T-nuts are nasty, and no use for good prescision.
The proper fixture for wood is barrel nuts, also called cross nuts.
The only downside is that it leaves an exposed (screwtop, the top of the nut, used for alignment).

I attach two images of how they are used normally...
 

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I thought the OP was looking for a way to Make a box he could open and close. I reccon with some gasket material, it may be good enough for a airtight seal, as you could tighten the nuts way beyond what you could do with one of those T nut jobbies.
 
I second Cal's suggestion to purchase a circular saw and guide. Presumably your cabinet is large, and long straight lines with a jigsaw are impossible. Even with a guide, the blade will bend. Thrift stores are good places to find used tools. I've always used 1.5" or 2" flat-head wood screws - #8 or #10 I think - on MFD. You'll need to pre-drill and counter sink the holes to keep the wood from splitting. As Loren42 said, screws do not "bite" well in MDF, which means you'll need a lot of them - like one very 3-4 inches. And it's easy to overtighten and strip the wood. I hope you have strong wrists! I've never taken the screws out.

Cal: I just so happen to have spent the day cutting boards for my big subs, and I want to not use screws for the first time. I'm using 3/4" oak plywood. I'm not clear on your suggestion. What is a cleat and what is a brad nail? When you say "fire the Brad nails" does that mean you use a nail gun? Do I need a nail gun? Any info would be helpful.

Thanks, Byron

And good luck qguy.
 
Cleats are the small strip of wood on the inside corners. See pic. They could be called inside corner blocking but that takes too much time to type.
Brad nailer is a small nail gun for finish work. The nails have almost no head.
Fire means use a gun yes.
Use 1 1/4" nails on 3/4" material and clamp (sometimes you can use straps) before you nail where possible.
Put braces (either stick braces or shelf braces) in front to back and side to side spacing them unevenly to break it up into different panel sizes
 

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I am planning to round off the corners. What if I add glue and put 3 regular nails to hold the pieces together until the glue sets and then remove the nails ?

Can someone explain to me e why I need to put several dozens screws when the glue would be enough ? unless I am wrong about the glue.

Thanks
 
Cal: Thanks, I'll try that, though I don't think I'll buy a nail gun.

qguy: I don't know that you'll need a wood screw every 3-4 inches in addition to glue. I mentioned it because it's what I've always done and you won't need clamps and it has always worked well with MDF. You stated in your first post you planned to use wood screws and didn't mention clamps. If you go with wood screws instead of nails or clamps, you will need a lot of them because each one will be weak. Also, if your cut is not super straight, the closely-spaced screws will pull the other board along the crooked cut's profile, reducing gaps.

It sounds like others have had good results using nails and/or clamps, so the screws are just another option.
 
What if I add glue and put 3 regular nails to hold the pieces together until the glue sets and then remove the nails ?

Sure but space your nails no more than about every 6 inches. No need to remove them unless you are planning to nail on the outside. Removing nails can damage your wood so most will use screws.

Can someone explain to me e why I need to put several dozens screws when the glue would be enough ? unless I am wrong about the glue.

Yes the glue is all you need but it has to be clamped. An excess of glue in a joint that is not tightly butted is weaker not stronger than a light film of glue squeezed tightly between boards. The screws are there in place of clamps. You can remove them later if you want to. In fact it will make filling the holes easier as filler often delaminates from the screw head.

I would think you still want to buy or even rent a brad nailer system. It really cuts down on the work assembling the boxes so you get to this stage much faster: :D
 

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clamps, cross-linked PVA

Many people use large clamps to assemble their cabinets. If you can borrow clamps it is a very good idea.

Clamps are not expensive, compared to the overall cost of cabinets and drivers. If you are going to build more that one set of speakers its worthwhile investing in a set.

Clamps can be adjusted to provide the just the right amount of pressure and the panels can be aligned perfectly (which is much harder to achieve with nails or screws).

I always use cross-linked PVA glue as it sets quickly and is thicker than normal PVA, so it is able to bridge and fill any gaps (unlike normal PVA which just soaks in or runs out the tiniest gaps, and requiring multiple reapplications to fill it up).
 
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