Large screw.. small head??

[DanDare]

I'm planning to fit some shelves into an alcove by making 'rails' either side + back out of 8mm steel square bar, with housings routed into the sides (and back) of the shelves.

The shelves are only 25mm thick, so I'm short of space to work with...

My problem: what screws can I use for a decent fixing (eg 2" number 12s), but which would have a head no bigger than 8mm, to match the the 8mm steel strip. Obviously I can countersink the steel, but I'm only routing a 10mm channel into the timber - to allow some wriggling into place, so the head really needs to be <8mm.

I'm fixing into masonry (plaster over brick... plaster not brilliant in places), and I've always just used plastic plugs - but would be very interested if another fixing would work!

Thanks all

Dan

 

[stevethejoiner]

Hi Dan
Well done for a very clear post, I can understand exactly what you are doing.
If the shelves are for normal static domestic use, ornaments, books etc I would use No8 or metric 4mm equivalent screws, 2”/50mm long will be fine into firm brick
If, as you say, you are supporting along the back and both ends then using No8/4mm shank screws 300mm centres would be fine.
Shelves take a downward static force and you will be amazed how strong a few 4mm shank screws are in sheer stress. Just try breaking one in half.

If you were going to load the shelves completely with books then maybe use No10/4.5mm screws, but No12s are OTT.
Good luck
Steve.

 

[SimonH2]

You could file the head down a bit, or use (carefully) a bench grinder if you have one with a fine wheel.

 

[DanDare]

Thanks for the responses.

Indeed I may resort to filing/grinding/cutting off the excess heads - but we're talking 7 shelves, 3 metal strips with 2 fixings each = 42 screws so I'd be at it for a while!!

The shelves will hold books - including one of large 'coffee table' books which are seriously weighty... The span is 1400mm.

Even so, I agree number 10 screws would themselves be strong enough, but I normally resort to number 12s because they seem to pull more firmly into brown plastic wall plugs... (and the red plugs are too short). Maybe there's a better fixing I can use for number 10s?

I could use window fittings - they have small heads, but I would have to screw them in rather than hammer in, so they pull the steel strips into the wall. I've never used them so I don't know if that would work (but I will get some and experiment...)

Thanks all

 

[stevethejoiner]

If you were hanging something from the ceiling I would agree that you would want to have heavy shanked screw that really bites into the plug, but you are only requiring to hold the metal box section to the wall. There will be no pulling on the screw head.
It's downward force on the shelf, and that will be distributed evenly over all the fixings. So I think you are worrying too much about the screw diameter fixings.
No 10 screws are more than adequate and if the heads are too big use No 8 but close up the centres and use more fixings.

 

[nickdsjnk]

I can't really recommend it from a health and safety perspective but I've reshaped screw heads by putting the screw in a drill and holding it to an upturned angle grinder. A poor mans lathe!

Spax do cylindrical head screws which might work?

http://www.spax.com/uk/craftsmen/sc...kopf-spax-t-star-plus-8-mm-vollgewinde-wirox/