Hi all,

i know that 1/4-20 will work, but will 5/16-18 bolts work? i will be using tee nuts and bolts to hold the sub in. the sub is the Fi Car audio BTL 12". basically just want the biggest bolt that will work. im sure there are plenty of people out there that can measure the mounting hole size and the rubber seal c'bore size. I just want to get the stuff on order and installe din the boxes before the sub gets here so its a quick intall. also i would assume the 18"s have the same sized mounting holes and c'bore in the rubber seal?

Thanks in advanced,

Anton Miller

Edited March 5, 201015 yr by Anton Miller

I use the 5/16 bolts (1.5" long) and t-nuts.

I use the 5/16 bolts (1.5" long) and t-nuts.

do you think you could have fit bigger ones in there? not that oyu would need to i guess... those ones should be good nough. i just want a really strong hold on the sub. also installing 3 18" btl's in a jeep and want ot make sure the bolts wont snap.

thanks

Well honestly this is my first time doing the t-nuts and bolts and that was the size that was referred to me all around the board. I dont think they would snap at all, screws wouldnt even snap (depending on the size you use). It just makes it easier to remove subs and not rip the wood up if you remove them a lot.

You are going to tear the surround up if you use a bolt that big unless you use a allen head bolt and a washer...

You are going to tear the surround up if you use a bolt that big unless you use a allen head bolt and a washer...

Do I have to use washer's with the allen head bolt? I like the way IT looks without washer smashing the surround, I was going without but seen you guy's talking so though I'd ask. Thanx Nick.

That's why I'd use 1/4 20's..

You have to trim the washers (chuck them in a vice and grind them down with a 40 grit flap disc) if you use them so they don't hang on the basket and on the surround..depends on what size basket you have as well. the 18's are a lot easier than the 12's and 15's.

So do you or don't you recommend going without washer's with the allen bolt?

You are going to tear the surround up if you use a bolt that big unless you use a allen head bolt and a washer...

it will be a socket head cap screw (allen head). i havent ordered anything yet and i can order w/e size i need and i know where to get custom washers i dont need to turn down. also why would the bolt tear up the surround? would deburring the bolt help? and what size o.d. washer would i need?

thanks,

Anton Miller

and i should probly share my favorite bolts and nuts and well anythign else sites. lol

MSC Flat Washers I use this place for anything i need next day. and i mean anything hardware related.

Mcmaster Carr This place is just awesome. they have everything! and its easy to find. this is where im buying my hardware for this. they even have copper and aluminum bars for buss bars.

I have more, but those two cover the Car audio spectrum of my life. Many more for my Tool design life. lol

and I guess the most important thing I would need is what size O.D. washer would i need to not "rip up" the surround.

Thanks again.

Your not going to need anything more than 1/4" 20. Once tightened down, the subwoofer won't be going anywhere.

Your not going to need anything more than 1/4" 20. Once tightened down, the subwoofer won't be going anywhere.

that might be for the best as i would like to bolt everything down with the same size bolt, i have a saz-3000 and im not sure if the 5/16" bolts would fit that either, maybe just getting the 1/4-20's would be for the best.

so i still would like to know the size of the washer. and would i need the washer with the 1/4-20's?

im gonna go ahead and hop in here, just got my first tracking email from fi... starting to get that nervous feeling in my gut 1/4 20's you say.. not sure exactly what that means but ill do some research.. will that be big enough to go thru a 1.5inch baffle? and safely mount an 18" btl ?

lets try the more specific approach, this is what ive found..

will this be sufficient? can anyone help me find a matching tnut for this or explain what im looking for exactly. appreciate any help.

im gonna go ahead and hop in here, just got my first tracking email from fi... starting to get that nervous feeling in my gut 1/4 20's you say.. not sure exactly what that means but ill do some research.. will that be big enough to go thru a 1.5inch baffle? and safely mount an 18" btl ?

seems to be what people are saying, but we are unsure as to which size washer we will need. i would use mcmaster for the 1/4-20 bolts, just serch socket head cap screws and then go form there, the 1/4 is the major diameter and the 20 is the thread pitch (threads per inch) you would need to specify the length of the screw, dont forget tee nuts.

lets try the more specific approach, this is what ive found..

will this be sufficient? can anyone help me find a matching tnut for this or explain what im looking for exactly. appreciate any help.

should work, just remember your going to need the tool that installs and removes this, gunna be extra money IIRC.

1/4 20 is fine. You don't need anything bigger then that..hell i've used drywall screws for years and in sheer those things are VERY weak..but i've never had a problem.

I would use something along those lines if you feel you must use bolts..and most thieves won't carry an alan wrench..

What's a T-nut? A toggle bolt? That's the only way I can figure being able to use a bolt in a wood box.

What's a T-nut? A toggle bolt? That's the only way I can figure being able to use a bolt in a wood box.

Parts-Express.com:

What's a T-nut? A toggle bolt? That's the only way I can figure being able to use a bolt in a wood box.

Parts-Express.com:�1/4"-20 Deluxe 6-Prong T-Nuts 50 Pcs. | t nut t-nut fastener insert nut machine screw

Cool, I haven't seen those before. I thought I was pretty up on my hardware since I've worked construction, but I guess you learn something everyday. Those look like they would be a lot better than using wood screws. So do you just drill a 5/16 hole and beat the T-nut in? I'm glad I found this thread, I'm going to use those in my next box.

I would always prefer threaded inserts over t-nuts.

McMaster-Carr

I use these and have never had any issues...

Screw Size 10, 1-1/8" Hex Head, Black Ox & Wax Finish from Madisound

I would always prefer threaded inserts over t-nuts.

McMaster-Carr

i dont like those because you have to bottom them out in a blind hole so they dont spin or push out. i like the t-nuts alot better because once you pound it in (straight) it wont spins and when you tighten the bolt down it draws the flange into the back side of the wood. its just preference though.

#12 Sheet Metal screws (not self drilling) from Lowes. Predrill with 1/8" drill bit. Works great.

Easy. . .never broke one. . .use the same holes over and over.

Brian