Problems drilling hard concrete and using screw anchors

[williamwright]

Ha!

Bill

[Jeff Layman]

Not sure about that.

As far as I could see, the chuck was rotating and I could hear and feel the hammer action. Out of interest, I weighed the chuck - it was 390g. Add around 30g for the 6mm bit and it comes to 420g. The biggest SDS bit I have is 22mm in diameter (200 - 250mm long?); it weighs 340g. I can't see that the 90g would make enough difference to affect the percussive/rotating action. Bigger SDS bits (25/30mm x 450mm) would weigh far in excess of the chuck weight, but they would work.

[John Rumm]

Not usually - in fact quite often the flutes on the add on chucks are designed such that the chuck will not hammer at all - even if the drill is set to hammer mode.

[John Rumm]

If its like the add on chuck I have, then the pattern of slots on the shank stop it seating far enough back in the SDS mechanism for the hammer to hit it. So in hammer mode, you would still feel the vibration from the anvil flipping back and fourth in the drill, but it would not be striking the chuck. (and the sound is different, since there is no metallic "clack" as the shank is struck).

Having said that, if yours works different to mine and does hammer with the chuck in, you may have a second problem, since a normal drill bit is not designed for >= 2 Joules of hammer energy per blow - so you might just shatter the carbide off the end anyway!

[John Rumm]

Not sure if mass alone would account for it. For example I have some 1m long SDS bits, and they are a good deal heavier than an add on chuck, but they drill ok.

[Nick Cat]

The one time I watched it done the chuck shattered on the first hit.

NT

[charles]

I, too, have a standard chuck for my SDS drill. I turn off hammer mode before using it.

[Roger Mills]

+1 Mine's like that.

[Roger Mills]

Indeed. If he's got an SDS drill, why on earth didn't he use an SDS bit?

I was confused about the drill size, too. If using 6mm bolts, the hole needs to be smaller than 6mm (4.5?) so that the threads will cut into the concrete. It's also a whole lot easier to screw these things in if you use an impact driver rather than hand tools.

[Jeff Layman]

I'll check tomorrow and compare shank patterns.

I hadn't considered that. Is the tip of an SDS drill bit of different/heavier construction than an ordinary masonry bit?

[Jeff Layman]

It's a good point, but I've never used the SDS drill for drilling - just using the pick and chisel points to break up lumps of concrete holding angle-iron fenceposts in the ground. I've never had any problem drilling using an ordinary hammer drill; as I mentioned I've used it for drilling lintels with rebars using the Bosch multipurpose bits (as well as ordinary TCT-tipped bits for drilling ordinary bricks). As it happens the SDS drill came with a selection of bits, but the smallest was 8mm.

The anchors have an overall diameter of 7.5mm. The solid "shaft" of the bolt is 6mm in diameter, so the threads cut into the concrete by 0.75mm on each side. I did see mention on one or two webpages of using an impact driver, but I don't have one (somewhere I have a manual impact driver, but I've never used it or have needed it. Perhaps that could have been used to drive in the anchor bolts).

[Dave Liquorice]

Yes...

[Cynic]

I really don't see why you didn't use resin anchors and save on all the fancying about.

[Andy Burns]

resin anchors still need holes drilling ...

[Jeff Layman]

Got a good link for that? I can see the SDS-fitting and often the flutes are different, but how does the SDS tip differ from an ordinary masonry bit tip? The Tungsten Carbide would be the same material, and AFAIAA the geometry is the same. I'm not questioning that SDS drills are more efficient at drilling/hammering than ordinary hammer drills, but I can't find anything which says the bit tips are any different.

[Dave Liquorice]

SDS drills are just a heavier construction, may used tougher steel.

It's not just the drill bit it's the machines action. An ordinary hammer drill just has a chatter plate that makes the end of the drill vibrate a bit. A SDS uses a pneumatic action to literally hammer the end of the drill, like hitting a cold chisel with a lump hammer.

The difference between the two is chalk and cheese. How long did it take to drill those 100 mm deep holes with your hammer drill? An SDS in the brick would be just a few seconds, the concrete perhaps 5, unless it's seriously hard, which the hammer drill would barely touch.

[charles]

Looking at some here, the flutes on SDS are much larger and the drill shaft is also larger, almost the full width of the tip. Both these would allow the tip to run cooler. Ordinary masonry drills are only meant to stand up tye hammer action of a normal power drill.

[Jeff Layman]

As you said, it is different.

So I wasn't getting the hammer action I expected. I must invest in a 6mm SDS drill bit!

[John Rumm]

Its a shame the re-used the name, since a manual impact driver is not really comparable to a powered one. (being designed to break free tight fasteners rather than quickly drive screws etc with high torque and low risk of cam out)

[John Rumm]

Yup, and the fluting on the shank different at well to clear waste faster. Some bits are two flute, and some are four. In some respects, SDS bits are more akin to a rawl tool style design - designed such that the masonry is pulverised by the high impact energy, and the rotation is basically there to clear the waste, and move to the next are to be hit. Its all about the hammer rather than the drilling.