Concrete screws- use of -how to.

[TRITON]

A bit back I had window fitters come in, replaced the old windows for new pvc dg. A month or so after, i was in one of the storage rooms(usually referred to as 'bedrooms' in normal houses), and in it i discovered one of the firms workers had left behind a stanley fatmax screw box containing a range of big what are concrete screws - 80mm,100mm,120mmx7.5mm and about 100 of each.

Naturally I was keen to return them to the company,, but ahem...seems to have slipped my mind, and as the windows were really expensive, and the fact nobody bothered to come to claim them, i seem to have been left with them.

So anyway. How do you use this type of screw ?

I dont remember them pre-drilling any holes, but they might have, so are they a type that needs a pre-drilled hole, or can you blast them straight in, maybe using an impact driver. It's a large Torx bit. Standard sharp point, no drilling notch in the end of it meaning possibly they need pre drilled, but if they are to be pre drilled, then why the sharp end point ? or is that just standard and nothing to be inferred from it.

Im sure they would also work for timber, maybe for outdoor use. So they'll always have a home somewhere, and it is a rather nice stanley kit box,im sure that will also come in handy.

 

[Blister]

I have used these, You do need to pre drill a hole then wind them in with a socket, They will only work in a good thickness of concrete and not near the edge or it will split off

 

[recipio]

Ideally for use with a drill/driver they are very useful and avoid the need for rawlplugs. They definitely need a 6 mm hole and can then be driven into concrete block or brick. I've put up lots of shelf brackets with them but the bracket hole usually needs enlarging and countersinking.. As far as I know the were originally designed for door frames but correct me if I'm wrong,

 

[ChaiLatte]

I'm sure they would also work for timber

Have a look at them or compare with a standard timber screw. The concrete ones will likely have the threads cut shallower on the core than a proper timber screw. The core needs to be larger so it does not shear when driving into the harder materials. The shallow thread depth may mean they do not grip well in timber.

Try to find out the make of them or look around for similar products. Fischer would have some technical information on the generic type.

The pilot drill size is quite important for their successful operation so it would be best to read the instructions on that. If driving into insulation block, you would use a smaller pilot drill (possibly no drill at all, hence the point but that risks splitting) than if driving into common brick.

For anything critical, it is best to do a test run. Drill a pilot hole and see how easily the screw drives in. Too little reistance, reduce the pilot size. Stops half way and lets the smoke out of the impact driver, make the pilot hole bigger.

 

[Phil Pascoe]

Ideally for use with a drill/driver they are very useful and avoid the need for rawlplugs. They definitely need a 6 mm hole and can then be driven into concrete block or brick. I've put up lots of shelf brackets with them but the bracket hole usually needs enlarging and countersinking.. As far as I know the were originally designed for door frames but correct me if I'm wrong,

Certainly for that type of usage. The beauty of them over Rawlbolts, sleeve anchors etc. is that they can be loosened off and tightened again if you've pulled something out of line.

 

[artie]

I've used these to fix "stuff" to walls. They worked well where the wall was good.

I also used 8 earlier this week in wood, I thought they would stand more sheer stress than a wood screw. Not in any danger of pulling out.

Remains to be seen.

 

[Phil Pascoe]

I would warn against buying the cheap ones - I had one lot that would strip the holes (in good quality block) before going dead. Stick to a reputable brand.

 

[MarkAW]

Use the same, but without plastic wall plugs. So a pre drilled hole of the right size is needed. They need more force to drive in so usually require a star shaped bit with an impact driver.

 

[MarkAW]

(deleted)

 

[Bingy man]

As above they are excellent as long as you drill into decent bricks -no good in weak or crumbling bricks or concrete. They are good for blind drilling because you don’t need to remove the timber or bracket etc that that you are fixing . I used the m10 version to support some new joists with heavy gauge angle iron. 10mm hole followed by the bolt

 

[Agent_zed]

I've used these https://www.toolstation.com/masonry-torx-frame-fixing-screw/p19150 multiple times without issue. Just fitted a new single door frame for my garage. 4 per side and it is rock solid. That was into brick. They are also holding my 1.8m bifold doors and a window frame. Dad and brothers have also used loads of them. Can't remember ever having an issue with them.

You have to make sure you drill the pilot hole deeper though as the last thing you want is for it to bottom out.

 

[user 36867]

I use these for frames when lineing a gagage or rooms drill hole and drive in with a hammer very fast and strong in breeze block and bricks.

 

[Fergie 307]

I have used them for a long time to secure wood framed buildings to a concrete base. I believe the original ones were branded Multi Monti. These had a very well defined thread, the first part of which was heavily serrated to cut into the concrete. This is the design you want. Unfortunately some of the ones available now seem to be very poorly made, so stick to a reputable brand. You just need to drill a hole the size of the core, and make sure it is maybe 20% deeper than the length of screw going into it. The reason for that is that the screw cuts a thread in the hole, and the resulting debris falls to the bottom so their needs to be space for it to avoid the bolt bottoming out. If using in concrete it needs to be well cured. Providing that is the case then, as long as it's decent concrete in the first place, you should be able to go very close to the edge without any danger of splitting, as they don't exert any sideways pressure, which is the big advantage over expanding fittings. You can also unscrew and refit them.

 

[Dave Moore]

As above they are excellent as long as you drill into decent bricks -no good in weak or crumbling bricks or concrete. They are good for blind drilling because you don’t need to remove the timber or bracket etc that that you are fixing . I used the m10 version to support some new joists with heavy gauge angle iron. 10mm hole followed by the bolt

Hi,
This version you have shown are specifically for brick and are brilliant in good solid brick. I used them in my loft to support steel channel which I fabricated for support when I removed the chimney breasts. Absolutely solid as the bricks were a solid brick.
Regards,
Dave

 

[Phil Pascoe]

I use these for frames when lineing a gagage or rooms drill hole and drive in with a hammer very fast and strong in breeze block and bricks.

The problem with them being you can't easily loosen them off and retighten them.

 

[Phil Pascoe]

I have used them for a long time to secure wood framed buildings to a concrete base. I believe the original ones were branded Multi Monti. These had a very well defined thread, the first part of which was heavily serrated to cut into the concrete. This is the design you want. Unfortunately some of the ones available now seem to be very poorly made, so stick to a reputable brand ...

+one for the reputable brand. I used them 20+ years ago mine were Thunderbolts.

 

[Owd Jockey]

I've used these in the past and often referred to them as Thunder or Tornado masonry bolts.

https://rapidtoolsdirect.co.uk/products/masonry-screw-bolt-8mm-x-60mm-drill-size-6mm-50pk-tornado

 

[recipio]

I bought a few boxes of Spax screws from Axminster a few years ago and still have them. They are Torx drive and the threads are tight and serrated. I'm guessing the pilot hole will be specific to each brand. They are also available in flat head and stainless steel. Highly recommended.

 

[HOJ]

If you do use them, drill a clearance hole in whatever you will be fixing, for me its generally timber windows & doors/frames (lined up with a full or 3/4 brick) then run in the masonry drill, I use a 150mm X 6mm drill bit, but not always with the hammer action engaged (I mostly fix into soft red bricks) countersink or bore out with a forstener bit, so you can fill/plug the head hole, and DONT use an impact driver to drive the screw home, gently does it, you have much more control and can tweak the frame/s rather than pulling them out of plumb or square.

Ignore all the above if your banging in rough timbers.

 

[RobinBHM]

Concrete screws are very fussy on drill bit size, I seem to remover I used 5.5mm and 6.0mm or could’ve been 6.5mm

The screws are 7mm diameter and the pilot hole size depends on the material hard brick or concrete go a 0.5mm bigger.

If they are too tight you can end up with three quarters of the way in and they won’t go in or back out