Fixing Speakers to MDF

[noidea]

We have a big av unit in the lounge that the tv sits on and there are side panels that I'd like to mount speakers on.
I have the brackets on order but my concern is making sure that the fixings I use for the brackets will be strong enough to hold the speakers.
The speakers are relatively light at just under a kg though I imagine there will be some torque as they sit a little away from the wall. The brackets have a couple of 4mm holes for the screws. Unfortunately the outsides of the MDF panels are visible to the room so I can't go all the way through with the fixings. I think they are around 25mm deep. Would a couple of wood screws be strong enough for this? Maybe flooring screws though it may be tough to get ones less than 25mm long?

 

[Gaspode_TWD]

Hi. by all means try screws first. Drill out a pilot hole first and use as broad a screw (deepest thread) as is practical with your brackets.
If you decide you're still not comfortable you may feel you can tolerate the look of bolts pushed through from the back. You'd need to drill right through (I'd suggest drilling from the back to the front). and use something like this Hex Bolt AVF-852527 Pack Of 10 (W)M10 x (L)40mm, AVF-852527
Or like these Cup Square Bolt AVF-851773 Pack Of 10 (W)M8 x (L)40mm, AVF-851773
I'd have the bolt head showing at the back because, hopefully, the speaker will hide the bolt end and the nut.

 

[noidea]

ah I hadn't thought about going through from the back as you're right that will give a much neater finish. I guess I could even countersink the bolt head and cover it with those little plastic discs.
Thanks!

 

[12harry]

M10 is a mighty large bolt to support 1kg. I'd expect something as small as M4 will do nicely, but use several to spread the load over an area - and use (pref. oversize) washers, to prevent the MDF being crushed.
Also, you wrote "4mm holes"...in Post1
Of course, Woodscrews are not suitable - but you can get special MDF screws that should hold the brackets....take them with you, if going to B&Q -so you can check the length & hole diameter, etc.
If you need to hide any fixing marks on the non-bracket side, then you can apply a veneer ( A wood-version of "Fablon" which is only a temporary fix and can be tricky. ), -or did you mean the MDF has a special finish...I don't quite understand.

Have you thought of gluing the speakers? It's not ideal, but NoMoreNails should fix it to almost anything (er, so I read!).....but then so does Evo-Stik, provided you apply to both surfaces and let it dry...just be sure it's aligned correctly* . . . it will be V-difficult to remove. However, I guess you're not expecting to remove M10 screws either . . . and they will need a 10mm hole, which I doubt suits the bracketry.... Always drill a smaller "pilot-hole" to act as a guide, even if using MDF-screws. A dab of olive oil will help then in.. Ideally, try this on a piece of scrap first - a word with the Sawman ( at B&Q) should get you a small piece of MDF for free. Practice on this.
Only then, tackle the real thing.

* For Gluing:- use some Masking tape to act as a positioning-guide, & remove the same day. Sellotape is too sticky and may leave a mark.

Hope that's some use and no insult...

 

[noidea]

Massively useful, thanks so much. I'm leaning towards using the MDF screws so I don't have to do anything about bolt heads on the other side. Your post has got me thinking that maybe a bit of no more nails as well as the screws will give it the extra security.
Thanks again

 

[noidea]

Finally got round to it. In the end I used threaded inserts to give a bigger diameter purchase in the MDF and normal 4mm machine screws to mount the brackets into them. Seems sturdy enough
Thanks for all advice