Best fastener to use when mounting sub drivers to MDF? - Page 2 - AVS Forum
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Old 03-31-2013, 05:25 PM
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Another option is to drill the hole, coat it with epoxy or polyester resin and then heat with a heat gun or hair drier.

This makes it watery and the MDF will suck it up; repeat to saturate and/or until the resin cures.

Then you can tap it and use socket head screws.

Probably easier, and certainly cheaper, but sometimes there's not enough edge distance.

Noah
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Old 04-01-2013, 05:33 AM
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Just use T-Nuts.

I've never had a T-Nut fail and you don't have to drill as big a hole in the wood as you would with a threaded insert.

Using CA (cyanoacrylate or "Crazy Glue") will greatly strengthen the wood around the hole, but you need to use the correct type for the best results. You should use "Thin CA" It's a very low viscosity liquid that wicks right into the wood. Normal Crazy Glue or Super Glue are much thicker than thin CA. You should be able to get thin CA at any good hobby shop or online.

If you chose to use CA to strengthen the hole, I would recommend drilling the hole, setting the T-Nuts in the holes by installing them and tightening them to set the teeth in the wood, then remove the bolts and apply the CA to the wood.

I'd also recommend "button head cap screws" over "socket head cap screws" whenever possible because button head cap screws typically have a larger diameter head for a given screw size.

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Old 04-01-2013, 06:07 AM
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I've never had any sub come loose only using wood screws into MDF. I've used everything up to and including the 21" Maeltrom and never had one come loose.

Pre-drill and tighten properly and 3/4" of wood screw X 8 screws will hold just about any subwoofer in place. If you think you'll remove and tinker a whole lot I would recommend t-nuts. I wouldn't want to re-use screw in MDF holes more than a couple times as their holding power diminishes each time they are used.

T-nuts can also be a pain if they are a little out of alignment after installed and cause the bolt to be crowded in the hole. Take particular care to make sure the t-nuts are centered in the mounting holes of the driver as a misaligned t-nut will ruin your day.

I use the Heavy duty T-nuts from PE when I do, and 10/32 rack mount screws for big sub drivers. With the big mounting holes of the SI these might be just the trick.
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Old 04-01-2013, 10:13 AM
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Quote:
Originally Posted by noah katz View Post

Another option is to drill the hole, coat it with epoxy or polyester resin and then heat with a heat gun or hair drier.

This makes it watery and the MDF will suck it up; repeat to saturate and/or until the resin cures.

Then you can tap it and use socket head screws.

Probably easier, and certainly cheaper, but sometimes there's not enough edge distance.

Kind of OT, but this sounds interesting. I have a door that the previous homeowner tried to rip off the hinges. One of the hinges on the top is loose and the hole is stripped. I've been trying to figure out how to fix the "loose hole". Maybe I should try shooting some glue or resin into the hole and using a heat gun.

My contribution to this thread: I've used screws and I've used T-nuts. Hard to say which I like ... worse. T-nuts are a pain, stick out too far into the cutout, don't pound well into MDF at all, hard to align, can come loose when you loosen a tightned-down driver. Screws chew up the hole and can strip the hole if you tighten it too much.
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Old 04-01-2013, 12:31 PM
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Quote:
Originally Posted by djkest View Post

Kind of OT, but this sounds interesting. I have a door that the previous homeowner tried to rip off the hinges. One of the hinges on the top is loose and the hole is stripped. I've been trying to figure out how to fix the "loose hole". Maybe I should try shooting some glue or resin into the hole and using a heat gun.

I've had a flag pole mounting bracket where the threaded hole in the wooden support was stripped. I tried stuffing the hole with wood glue and tooth picks, but it didn't hold the screws for long on a windy day.

Epoxy putty worked well. Loctite, J-B Weld, and maybe others make it. Drill out the stripped screw hole so its large enough (at least ¼") to easily fill with the putty. When its cured, you can sand, drill or tap threads into it. Its always held.



For threaded inserts in MDF or plywood, I like using the knife-edge inserts. I've had poor results with T nuts.

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Old 04-01-2013, 12:57 PM
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I have taken to cutting out a ring of ply and splitting it. Feed it through and glue and clamp. Just use standard 2" wood screws after that.

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Old 04-01-2013, 01:50 PM
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Quote:
Originally Posted by djkest View Post

Kind of OT, but this sounds interesting. I have a door that the previous homeowner tried to rip off the hinges. One of the hinges on the top is loose and the hole is stripped. I've been trying to figure out how to fix the "loose hole". Maybe I should try shooting some glue or resin into the hole and using a heat gun.

CA is great stuff, but it's no good at bridging or filling gaps (by itself). If you're filling a hole, you're much better off using an epoxy. If you can, get 30 minute 2 part epoxy because the longer it has to set, the deeper it can penetrate the wood. Heating it with a heat gun will also thin it out, but keep in mind that heat does tend to accelerate the curing process.

John
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Old 04-01-2013, 02:32 PM
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A quick fix is just to stuff the hole with toothpicks and put the screw back in.

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Old 04-01-2013, 03:52 PM
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Quote:
Originally Posted by djkest View Post

Kind of OT, but this sounds interesting. I have a door that the previous homeowner tried to rip off the hinges. One of the hinges on the top is loose and the hole is stripped. I've been trying to figure out how to fix the "loose hole". Maybe I should try shooting some glue or resin into the hole and using a heat gun.
J-B KwikWood is an epoxy putty that you stuff in the hole. It is hard in 1 hr. Works great.

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Old 04-01-2013, 04:17 PM
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I forgot to mention that I recently noticed this at Home Depot

http://www.homedepot.com/p/t/100376253?productId=100376253&storeId=10051&langId=-1&catalogId=10053&cm_sp=BazVoice%2d%5f%2dRLP%2d%5f%2d100376253%2d%5f%2dx

Simpler, but if you're in a hurry using the method I described above with fast-setting epoxy would be quicker.

Another way is to drill the holes oversize and glue in hardwood dowels, which can also be tapped.

Noah
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Old 04-01-2013, 04:46 PM
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Quote:
Originally Posted by desertdome View Post

J-B KwikWood is an epoxy putty that you stuff in the hole. It is hard in 1 hr. Works great.


That stuff is so good it should be in everyone's tool box. It works great for repairing a stripped screw hole in both MDF and plywood, had my fair share over the years. So many uses and a little goes a long way, I even reshaped a corner in MDF that got crushed when the cabinet fell, could not even tell after it was sanded and painted.

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Old 04-02-2013, 12:17 PM
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The last time I used epoxy paste was decades ago; it didn't adhere well.

The KwikWood does?

Noah
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Old 04-02-2013, 12:26 PM
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in my general expirence yes it does, you can make it adhear better by drilling some very small finger holes into whatever you are patching to get it to grab better. We used it all the time when i used to work for a furniture manufacturer. comes in a variety of colors and you can kinda mix it to get it darker or lighter. sands great when dry and finishes just like normal wood
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Old 04-02-2013, 03:24 PM
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You guys are awesome. My wife is going to be thrilled when I fix the door. We've lived with this crappy door (that we use all the time) for far too long! (3 years)

Okay /hijack
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Old 04-02-2013, 09:43 PM
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In a pinch, break a couple of wooden toothpicks to correct length, stuff in stripped hole, and the screw will likely hold for a good while. Tossing some wood glue, super glue, epoxy or whatever you have in there with the toothpicks helps even more.

I actually prefer this for anything but heavy duty use over wood putty as it is quicker and less cleanup.

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Old 04-10-2013, 06:59 PM
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Just wanted to add I finished my 2nd box, a 18" sub box 4 cu ft flat pack, and again used these.
photo%25201a.jpg

Like I posted earlier, I used a 3/8" dia drill not a 11/32" drill, as 11/32 is not a std drill size in many drill bit sets.
This time, no glue.

IMO I'd always use these, quick, easy, robust.
Bites into the MDF, solid there.
photo%25202b.jpg

photo%25204b.jpg
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Old 04-19-2013, 11:27 AM
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Thanks for all this good fastener info Mike.

I'll be doing 4 sub boxes and I thought I'd look around to see if I could find these or similar inserts for cheaper (since they're about a buck apiece at Home Depot). It seems the hammer-in types are a bit harder to find online than the screw-in ones, but I finally found some at Parts Express here (part number 081-1096 if the link goes bad). These are $11.95 for a package of 50. Amazon also sells them here, and they seem to charge a bit less for shipping than PE does for some reason.

Anyway, I just thought I'd pass that along.
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Old 04-19-2013, 01:56 PM
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Hate to hijack a thread but on a related question, how do you guys get your bolt holes straight and lined up with the holes in the driver on a sub. I have tried doing it with my drill press and free hand with the hand drill but always end up with one bolt that doesn't line up right or won't thread in properly/cross threads.
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Old 04-19-2013, 02:08 PM
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Google "centering drill bit". Cabinet makers use them.
bluer101 likes this.
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Old 04-19-2013, 02:11 PM
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Quote:
Originally Posted by mtbdudex View Post

Just wanted to add I finished my 2nd box, a 18" sub box 4 cu ft flat pack, and again used these.
photo%25201a.jpg

Like I posted earlier, I used a 3/8" dia drill not a 11/32" drill, as 11/32 is not a std drill size in many drill bit sets.
This time, no glue.

IMO I'd always use these, quick, easy, robust.
Bites into the MDF, solid there.
photo%25202b.jpg

photo%25204b.jpg

Do you put these on the outside of the double baffle? Seems like you could do it on the inner one and then sandwich it in and only drill a hole big enough for the bolt .. that would make it permanent.
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Old 04-19-2013, 02:56 PM
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Quote:
Originally Posted by blah450 View Post

I am working with 18" Dayton drivers and MDF cabinets.

I saw SPAX #10 by 1.5" somewhere.
Anyone else have some really solid suggestions?
Predrilling is fine with me if needed.

Quick and dirty.

Drill oversize screw holes and fill them with plumber's epoxy.

http://www.lowes.com/pd_23533-138-31270_4294822081__?productId=3132883



Drive the screws most of the way in after the epoxy has partially hardened. Cinch down when it is really hard.

FWIW, also works with cement, drywall, plaster, etc.
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Old 04-19-2013, 03:08 PM
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Originally Posted by pauleyc View Post


Do you put these on the outside of the double baffle? Seems like you could do it on the inner one and then sandwich it in and only drill a hole big enough for the bolt .. that would make it permanent.

Look at post 12 here,I have more details pictures

I used the actual speaker as jig for holes, drilled thru with 1/4" drill, then on the inner baffle I drilled 3/8" 1/2" deep coming up from "inside the speaker box.
All holes line up perfectly that way.
Further, I then used each screw to pull the fastener into the hole, so simple and easy.
It is then 90deg and square.
http://www.avsforum.com/t/1464218/best-fastener-to-use-when-mounting-sub-drivers-to-mdf#post_23106584

Of course I did this before the baffle was glued/attached.
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Old 04-19-2013, 04:25 PM
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Quote:
Originally Posted by pauleyc View Post

Google "centering drill bit". Cabinet makers use them.

I think he is asking how to drill the hole a perfect 90 degrees into the wood. Get a BIG GATOR drill guide, you can find them at wood craft. If you have a drill press, get a piece of wood, drill a hole in it and use that as a guide.

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Old 04-19-2013, 08:36 PM
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Quote:
Originally Posted by pauleyc View Post

Google "centering drill bit". Cabinet makers use them.

I have a set and didn't get the best results the one time I used them as the driver mounting flange was thin and the center of the bit guide bottomed out on the wood.

Thanks
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Old 04-20-2013, 04:06 AM
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Quote:
Originally Posted by Jon S View Post

Quote:
Originally Posted by pauleyc View Post

Google "centering drill bit". Cabinet makers use them.

I think he is asking how to drill the hole a perfect 90 degrees into the wood. Get a BIG GATOR drill guide, you can find them at wood craft. If you have a drill press, get a piece of wood, drill a hole in it and use that as a guide.

A simple DIY 90deg jig to keep holes square when drilling by hand:
(via member d-c)
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Old 04-20-2013, 04:19 AM
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Quote:
Originally Posted by djarchow View Post

Quote:
Originally Posted by pauleyc View Post

Google "centering drill bit". Cabinet makers use them.

I have a set and didn't get the best results the one time I used them as the driver mounting flange was thin and the center of the bit guide bottomed out on the wood.

Thanks

I use a pilot point drill bit when drilling the initial hole into the wood.


If I want to drill a bigger hole into existing hole I then use the traditional drill bit, it's chamfer will help you self center
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Old 04-21-2013, 06:03 PM
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Quote:
Originally Posted by blah450 View Post

I am working with 18" Dayton drivers and MDF cabinets.

I saw SPAX #10 by 1.5" somewhere.
Anyone else have some really solid suggestions?

T-nuts inside the cabinet. You can epoxy them in so there's no way they can come loose.



Attractive button head (or socket head) cap screws on the outside.

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Old 05-22-2013, 12:49 PM
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Quote:
Originally Posted by 14U2NV View Post

Just use T-Nuts.

I've never had a T-Nut fail and you don't have to drill as big a hole in the wood as you would with a threaded insert.

Using CA (cyanoacrylate or "Crazy Glue") will greatly strengthen the wood around the hole, but you need to use the correct type for the best results. You should use "Thin CA" It's a very low viscosity liquid that wicks right into the wood. Normal Crazy Glue or Super Glue are much thicker than thin CA. You should be able to get thin CA at any good hobby shop or online.

If you chose to use CA to strengthen the hole, I would recommend drilling the hole, setting the T-Nuts in the holes by installing them and tightening them to set the teeth in the wood, then remove the bolts and apply the CA to the wood.

I'd also recommend "button head cap screws" over "socket head cap screws" whenever possible because button head cap screws typically have a larger diameter head for a given screw size.

John


This is exactly what I've used on every single one of my builds. Works perfectly although alignment can be a bit tough on occasion if you aren't perfect when doing your initial tapping but otherwise its great. Sucks the driver to the wood and the t-nut isn't exactly going to suck through the MDF or plywood from the back! I have had hurricane nuts pop out and that's just not fun!

Scott
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Old 05-23-2013, 11:20 AM
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Hurricane nuts ime work much much better than the t nuts. I've had too many t nuts have the forks fold over and spin too many times. With some epoxy on the hurricane nuts they hold very well.

One other note. Whether using hurricane nuts or t nuts make sure to run a tap through them before final driver installation to ensure that the threads are cleaned out. This is not an optional step.
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Old 05-23-2013, 12:41 PM
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Install closed cell foam in the recess, set the driver on top of the closed cell foam gasket, pre-drill the holes using the right diameter drill and insert #10 pan head machine screws using a cordless drill that has an adjustable clutch feature.

No need to critically center pre-drilled holes and/or pre-install T or hurricane nuts.

A #10 machine screw in a pre-drilled hole through 19mm of MDF has a withdrawal capacity in excess of 300 pounds. Multiplied by 8 of them, the driver is going nowhere and the installation is air tight.
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