Advice on 6.5mm Concrete Screws - pilot hole / powered screwdriver

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Guys

I bought some 6.5mm (100mm long) concrete screws (which came with a free Torx T30 "bit). I decided to do some tests on some old masonry (before I do the "real" job. Glad I did, because when drilling Pilot holes with 6mm SDS masonry drills, I found that the screws would only reach about half way before my Impact Driver (Worx - WX250) - simply gave up, and just spun without turning the bit (so it miust have a clucth). The same happened with my battery drill-driver, (used in in screwdriver mode of course).

I COULD actully turn the screws by hand (with some effort), but on the actual job that would be a real pain as there are lots of screws required (French windows x 2 units).

(Note - the pilot holes did extend slightly beyond the length of the screws i.e. slightly beynd the 100mm mark, so thats definately not the reason I was getting "resistence" forom the impact fdriver & drill-driver)

Just FYI on the pilot holes - I was using an SDS drill (in drill mode) to drill the pilot holes. Whe I trie it in SDS combined drill/hammer mode, it just shattered the masonry, but I'm happy just with frill mode, as it driled the pilot holes fine

So:
1) Am I using the correct pilot hole? (I'm using 6mm , should I be using 6.5 ?mm)
2) Should I be using a "meatier" powered screwdriver ? I am a bit of a novice here, but I thought impact drivers were meant to be quite powerful, but obviously, not for this type of application ? (I assume?). Are there any more powerful bits of kit I should be using ?

Thanks in anticipation for any advice.
 
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We use the 7mm concrete screws with a 6mm sds masonry pilot hole. Never had any issues using a 18v cordless drill to do them up ( used a 12v before to!) Never needed to use impact driver) . Only time to be careful is into red brick, as dust tends to jam the screws up easily , so drill with masonry bit a couple of times
 
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Guys

I bought some 6.5mm (100mm long) concrete screws (which came with a free Torx T30 "bit). I decided to do some tests on some old masonry (before I do the "real" job. Glad I did, because when drilling Pilot holes with 6mm SDS masonry drills, I found that the screws would only reach about half way before my Impact Driver (Worx - WX250) - simply gave up, and just spun without turning the bit (so it miust have a clucth). The same happened with my battery drill-driver, (used in in screwdriver mode of course).

I COULD actully turn the screws by hand (with some effort), but on the actual job that would be a real pain as there are lots of screws required (French windows x 2 units).

(Note - the pilot holes did extend slightly beyond the length of the screws i.e. slightly beynd the 100mm mark, so thats definately not the reason I was getting "resistence" forom the impact fdriver & drill-driver)

Just FYI on the pilot holes - I was using an SDS drill (in drill mode) to drill the pilot holes. Whe I trie it in SDS combined drill/hammer mode, it just shattered the masonry, but I'm happy just with frill mode, as it driled the pilot holes fine

So:
1) Am I using the correct pilot hole? (I'm using 6mm , should I be using 6.5 ?mm)
2) Should I be using a "meatier" powered screwdriver ? I am a bit of a novice here, but I thought impact drivers were meant to be quite powerful, but obviously, not for this type of application ? (I assume?). Are there any more powerful bits of kit I should be using ?

Thanks in anticipation for any advice.

the pilot drill size depends on the material, soft brick use a 5.5mm drill, for hard materials try a 6mm or 6.5mm (or 6mm and go in and out a few times.

sometimes wax on the screw helps or spray with wd40 on the thread.
concrete screws are a bit of a fine line - it’s annoying in hard bricks, if it’s that little bit too tight even an 18v impact can run out of grunt and you can’t get them in or out.

another trick is to wind them in 3/4 of the way, reverse out then go all way in
 
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Ive been using correct size pilot for the concrete screws i’m using in sandstone and concrete block and the biggest % of screws jam before going the full distance. If I then push the pilot back into the hole it only goes part way in so has to be re drilled again...this can be repeated a few times before the screw goes full depth. When I try and force the jammed screw the bit shears off
 
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Ive been using correct size pilot for the concrete screws i’m using in sandstone and concrete block and the biggest % of screws jam before going the full distance. If I then push the pilot back into the hole it only goes part way in so has to be re drilled again...this can be repeated a few times before the screw goes full depth. When I try and force the jammed screw the bit shears off
I think concrete screws have limited application, In really hard materials they just can’t cut a thread and bind.

When Ive struggled, I go back to an expanding plug type fixing
 
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I think concrete screws have limited application, In really hard materials they just can’t cut a thread and bind.

When Ive struggled, I go back to an expanding plug type fixing
I had to persevere and keep re drilling to clear the dust as the threaded screws into thin sandstone laid with lime/clay mortar exerts less stress than expanding fittings which can blow them apart
 
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I had all these problems when I used them the first time, which happened to be into grey engineering bricks. However a phonecall to a colleague elicited the question 'How are you clearing the dust?' and an explanation it needs to be with air blown into the back of the hole and a description of how he uses a 'track pump' with a fine tube.
Returning the following day I'd found a plastic tube similarto a WD40 nozzle and taped it into one of the several nozzles in my track pump. Very cumbersome but the bolts went straight in after that.
I also learned very quickly to not give them 'just a bit more' with a spanner like I would with an expanding bolt as they shear off.

I love them now and go to them before anything else.
 

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