Best fastener to use when mounting sub drivers to MDF? - AVS Forum
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post #1 of 60 Old 03-19-2013, 05:17 PM - Thread Starter
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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.
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post #2 of 60 Old 03-20-2013, 10:44 AM
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I'm going to Home Depot later. Can someone confirm that spax#10 are the way to go?
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post #3 of 60 Old 03-20-2013, 11:46 AM
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I would get a panhead/buttonhead screw. I would be worried about the tapered flat head expanding the screw holes in the driver frame.

I normally use cap screws and hurricane nuts or threaded inserts for heavy drivers like subs. For smaller drivers like mids, tweeters etc. I just use a black oxidized panhead screw like Parts Express sells.
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post #4 of 60 Old 03-20-2013, 12:13 PM
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Well I used some screws and that was a bad idea on my 18Subwoofer.. I am going to replace the screws with t-Nuts..

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post #5 of 60 Old 03-20-2013, 03:50 PM
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I like threaded inserts and socket-cap machine screws. The reasons are that they look cooler, and provide fewer opportunities to puncture the surround and cone than a screwdriver with a sharp edge or a pointy tip do.
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post #6 of 60 Old 03-20-2013, 05:00 PM
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Quote:
Originally Posted by djarchow View Post

I would get a panhead/buttonhead screw. I would be worried about the tapered flat head expanding the screw holes in the driver frame.


I ended up getting some #10 pan head screws. Thanks.
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post #7 of 60 Old 03-20-2013, 05:58 PM
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as i said in your other thread i used 1.5" #6 wood screws on my 18s, I know others have used the #10 1.5" Spax Screws as well

i predrilled for mine and they are in tight i really don't think they are going to have issues
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post #8 of 60 Old 03-20-2013, 06:54 PM
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You didn't mention what sub your using but if it is one of the Stereo Integrity 18" subs make sure you check first if the head of the screw is big enough. Some subwoofers like the SI 18" have a little bigger than normal bolt holes so the head of the screw will need to be a little bigger or you will have to use washers. There are some others subs like this as well but the only 2 I have ever encountered was the SI 18" and the discontinued Maelstrom-X 18" and 21".

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post #9 of 60 Old 03-21-2013, 04:02 AM
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I am curious to know what is the best method of mounting a driver into MDF if you know that you are going to have to take it out of the box a few times? Wouldn't it be best in that situation to use threaded inserts as opposed to just plain old screws because if you go with regular screws that are just screwed into the MDF then won't the screw holes waller out and make it harder to get them to stay in tight?
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post #10 of 60 Old 03-21-2013, 04:28 AM
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I used Spax #14 by 3 inch in my MDF. Course, I don't plan on taking the driver out unless something goes wrong. If you plan on mounting and unmounting your driver more often, then threaded inserts or some other type of fastener would be more appropriate.

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post #11 of 60 Old 03-21-2013, 04:48 AM - Thread Starter
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In my case, I am working with an 18" Dayton sub driver.
I would like to make sure the head overlaps the driver flange enough...that is the right way to mount it, yes?

If that is the case, it always seems like bugle-head screws (drywall screws) can widen a hole if torqued too much.eek.gif

Would be cool to see some macro pics of the screws on DIY 18"/21" mounted drivers.
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post #12 of 60 Old 03-21-2013, 04:59 AM
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I used these;


Here was my method/process;
Quote:
Originally Posted by mtbdudex View Post

What's a build w/o some actual pictures?

Here is the 15" D2 Drwg:


step 5a: Dry fit front baffle inner and outside piece, put 15" driver in place, use 3 thin items to position driver centered


step 5b: Pre-drill front baffles for 1/4-20 screws and thd fasteners, using box as a holding jig and the 15" driver holes as drill template - be careful when doing this, here you see some sawdust from drilling

Outside front

and the inner front all done same time and line up nicely


step 5c: carefully remove 15" driver - do this by pulling up outside front piece with one hand and then remove driver
step 5d: remove both outside and inner front baffles,
Lesson learned: Watch where your braces are...I had my screw holes lined up at 12/3/6/9 o'clock....and they each went into the brace end just slightly.
I had to open them up just a tad.


step 5e: drill 3/8 hole just 1/2 deep in the "inner" side of the inner front baffle, this is where the 1/4-20 thd fastener will go next step
I used these from Lowes, The Hillman Group 4-Count 1/4"-20 Zinc Plated Standard (SAE) Wood Insert Lock Nuts http://www.lowes.com/pd_148251-37672-881674_0__?productId=3013891&Ntt=the+hillman+group+1%2F4%22-20+wood+insert&pl=1&currentURL=%3FNtt%3Dthe%2Bhillman%2Bgroup%2B1%252F4%2522-20%2Bwood%2Binsert&facetInfo=


step 5f: install thd fasteners into inner front piece, use 1/4-20 screws with washer to pull the thd fastener into the inner baffle from outside baffle side, put small amount of glue into each hole before doing this
>>This will ensure the 1/4-20 thd fasteners are perpendicular to the front baffle assy and also exact alignment to driver

All 8 done

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post #13 of 60 Old 03-21-2013, 05:49 AM
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Quote:
Originally Posted by blah450 View Post


Would be cool to see some macro pics of the screws on DIY 18"/21" mounted drivers.

i can get you these when i get home if you really want them
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post #14 of 60 Old 03-21-2013, 06:44 AM - Thread Starter
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Many thanks Mtbdudex (missed your thread with these!) and others so far.
Have appreciated the dialogue with Sibuna:cool:.
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post #15 of 60 Old 03-21-2013, 09:13 AM
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actually there are lots of options, this thread is good to collect them - with example/pictures to guide fellow DIY'ers, then it should be added as a link to the DIY FAQ sticky here.

Thx for starting the thread.
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post #16 of 60 Old 03-21-2013, 05:06 PM
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not sure how much these are gonna help you

#6 1.5" wood screws - Dayton 18 HO



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post #17 of 60 Old 03-21-2013, 05:10 PM
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I used #6 1.5 inch threaded drywall screws as well for my SIs.
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post #18 of 60 Old 03-21-2013, 05:26 PM
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Quote:
Originally Posted by DS-21 View Post

I like threaded inserts and socket-cap machine screws. The reasons are that they look cooler, and provide fewer opportunities to puncture the surround and cone than a screwdriver with a sharp edge or a pointy tip do.

+1



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post #19 of 60 Old 03-21-2013, 05:42 PM
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Quote:
Originally Posted by bhazard View Post

I used #6 1.5 inch threaded drywall screws as well for my SIs.

Did you use washers? If not then you might want to double check if the screws are holding well since the SI 18's mounting holes are bigger than normal. I used these with the first pair of SI 18's but had to use washers as I could pull the screw heads through a few of the openings: http://www.madisoundspeakerstore.com/black-ox-wax-finish/screw-size-10-1-1/8-hex-head-black-ox-wax-finish/
I also have some TC Sounds mounting screws as well and they can go through the mounting holes as well. I just grabbed a few drywall screws and the heads on those will go through the mounting holes on the other 2 SI 18's I have that are just sitting around waiting for an enclosure.

I know check all the subs mounting holes when I first get them to make sure I use the proper screws. It happened to me when I first got a Maelstrom X 18" sub and mounted it with the TC Sounds screws. It was playing fine behind the couch I was sitting on when all of a sudden I felt the driver hitting against the back of the couch. When I looked the bottom screws had gone right through the mounting holes and half the sub came off, only being held on by a couple of screws at the top.

The Dayton RS18's are fine with any screws, smaller mounting holes. The only 2 subs I have had that have larger than normal mounting holes are the Maelstrom-X 18" and 21" and the SI 18".
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post #20 of 60 Old 03-22-2013, 05:02 AM - Thread Starter
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Found the below two items.

The bolts are from Home Depot (or many different places)...Hillman brand, 2 per pack...1/4-20 x 1" Socket Head Cap Screws. I only went with one inch on these because there's only a 3/4" baffle thickness where the driver flange is seated. You can get them in stainless or black oxide finish.
You could, of course, find coarse thread "screw-point" variants of these if you are going to screw down the driver and not ever or often see the need to remove it for any reason.

I liked the idea of being to unbolt as often as I wished anytime and not worry about holes becoming bigger flaky holes in MDF...so I am using a 3/8" pilot hole and inserting the below 1/4-20 knife thread brass inserts. You can find these for about 50 cents each at many different places including McFeely's online. You can insert these from the back or front of the work piece.



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post #21 of 60 Old 03-22-2013, 06:44 AM
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In case the site is unknown to anyone, mcmaster.com has a wide selection of threaded inserts. Here is the main category. The Tapping Inserts for Wood subcategory has most of the types mentioned in this thread. I personally prefer the hex-drive variety over the slotted for ease of installation.

In addition to staying put more reliably, these are narrower overall compared to T-Nuts. You will sometimes see the mounting holes quite near the driver cutout hole, causing the wide flange of T-Nuts to encroach on this space.
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post #22 of 60 Old 03-22-2013, 08:37 AM
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Quote:
Originally Posted by baniels View Post




That's awesome!

As for me, I ended up with 2.5" #10 sheet metal screws. My baffles are only ~1" thick, so I will be adding extra blocks of (real) wood to the screw hole locations. I wanted to try a threaded insert or something, but it seems that these screws have an odd thread type. They aren't compatible with the #10 hurricane nuts I already had laying around.
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post #23 of 60 Old 03-22-2013, 08:46 AM
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Just a tip for anyone if they are interested. Make your mounting panels out of plywood. All your mounting problems have just been solved. No need for anything but wood screws now! biggrin.gif:D

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post #24 of 60 Old 03-22-2013, 09:36 AM - Thread Starter
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N8DOGG....yeah, right on. I saw a couple of build threads where one person made the "under-baffle" from plywood and the "topper" from MDF to match the rest of the cabinet.

Of course, there's always the option of the entire baffle being made from ply as you indicated, or the entire cab for that matter, eh?

I had originally started the thread because of the interest in Erich's MDF flat packs...particularly those for heavier weight subwoofers.

If I had the aptitude and tools available, I probably would have made my two enclosures from BB ply.

Appreciate everyone's responses to date!!
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post #25 of 60 Old 03-22-2013, 09:46 AM
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Quote:
Originally Posted by mjaudio View Post

Did you use washers? If not then you might want to double check if the screws are holding well since the SI 18's mounting holes are bigger than normal. I used these with the first pair of SI 18's but had to use washers as I could pull the screw heads through a few of the openings: http://www.madisoundspeakerstore.com/black-ox-wax-finish/screw-size-10-1-1/8-hex-head-black-ox-wax-finish/
I also have some TC Sounds mounting screws as well and they can go through the mounting holes as well. I just grabbed a few drywall screws and the heads on those will go through the mounting holes on the other 2 SI 18's I have that are just sitting around waiting for an enclosure.

I know check all the subs mounting holes when I first get them to make sure I use the proper screws. It happened to me when I first got a Maelstrom X 18" sub and mounted it with the TC Sounds screws. It was playing fine behind the couch I was sitting on when all of a sudden I felt the driver hitting against the back of the couch. When I looked the bottom screws had gone right through the mounting holes and half the sub came off, only being held on by a couple of screws at the top.

The Dayton RS18's are fine with any screws, smaller mounting holes. The only 2 subs I have had that have larger than normal mounting holes are the Maelstrom-X 18" and 21" and the SI 18".

Forgot to say my whole cab is made with birch, triple baffle recessed. Once drilled in, I checked and both drivers weren't going anywhere. I assumed MDF would have held the same.
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post #26 of 60 Old 03-22-2013, 09:51 AM
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Quote:
Originally Posted by blah450 View Post

I had originally started the thread because of the interest in Erich's MDF flat packs...particularly those for heavier weight subwoofers.


Gluing a piece of scrap wood under each screw hole seems like it would be a good compromise. I'm going to do that with one of EricH's flat packs. I don't have the tools to cut out an entire enclosure, but I can saw off a piece of scrap.
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post #27 of 60 Old 03-22-2013, 11:10 AM
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Quote:
Originally Posted by bhazard View Post

Forgot to say my whole cab is made with birch, triple baffle recessed. Once drilled in, I checked and both drivers weren't going anywhere. I assumed MDF would have held the same.

Sorry, I wasn't very clear. The screws held in place just fine in the wood, just that the head of the screw slipped right past the mounting holes of the sub because the screw heads were too small. All the drywall screws I have, about 6 boxes, the heads of the screws just barely make contact with the mounting holes of the SI 18" and if you put enough pressure they will slip past.

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post #28 of 60 Old 03-22-2013, 07:42 PM
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Quote:
Originally Posted by blah450 View Post

Found the below two items.

The bolts are from Home Depot (or many different places)...Hillman brand, 2 per pack...1/4-20 x 1" Socket Head Cap Screws. I only went with one inch on these because there's only a 3/4" baffle thickness where the driver flange is seated. You can get them in stainless or black oxide finish.
You could, of course, find coarse thread "screw-point" variants of these if you are going to screw down the driver and not ever or often see the need to remove it for any reason.

I liked the idea of being to unbolt as often as I wished anytime and not worry about holes becoming bigger flaky holes in MDF...so I am using a 3/8" pilot hole and inserting the below 1/4-20 knife thread brass inserts. You can find these for about 50 cents each at many different places including McFeely's online. You can insert these from the back or front of the work piece.




How good did those coarse thd insert bite into the MDF?
I was looking at them, but felt MDF might crack or something - I have no data/experience to back that up just a swag - so went with what I posted above.
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post #29 of 60 Old 03-24-2013, 10:05 PM
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Quote:
Originally Posted by baniels View Post

Quote:
Originally Posted by DS-21 View Post

I like threaded inserts and socket-cap machine screws. The reasons are that they look cooler, and provide fewer opportunities to puncture the surround and cone than a screwdriver with a sharp edge or a pointy tip do.

+1




That is very efficiently-done overkill bracing!

As for getting screws to stay in MDF, there's also the Geddes method. Basically, pour a couple drops of superglue down the screw hole, quickly run a wood screw in and out. Basically creates a plastic insert. I've only tried it once, but it worked as advertised. If I didn't prefer the look and safety of socket-caps (SO much harder to have the screwdriver slip and puncture a cone or surround than a slot or Phillips head!) I'd likely just do that. A few sacrificial screws are cheaper than metal inserts.

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post #30 of 60 Old 03-31-2013, 11:27 AM - Thread Starter
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Finally got around to drilling a hole in a test scrap of MDF and trying out the brass knife thread inserts. Had some trouble with them not wanting to pull through cleanly. Opted out of that after trying several different means of mounting including opening up the pilot hole a little more. Rather than mess around with having inserts align perfectly with screws. I followed the lead of others and just went with screws...just too darn quick and convenient! I found the below pocket head screws at Lowes. I used #8 by 1.5", the head was easily wide and the underside flat enough to securely hold the flange of the Dayton 18" HO subwoofers. Being pocket-hole screws, it was a nice, wide, deep thread that held in the MDF very well. I did drill pilot holes despite the "cut-point" of the screws allowing for an easy start.

After returning the other hardware, total cost for a pack of these screws was $5.

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