Problems drilling hard concrete and using screw anchors

[The Natural Philosopher]

SDS is all about how the drill is held and nothing about the tips at all. But you can (it appears) get a better hammer action on an SDS. So as usual Liqour-ish is wrong..

[Jeff Layman]

I'm not sure I could have used a powered impact driver even if I had one. The baseplate is 100 x 100mm. Welded asymmetrically to that is the

40 x 40mm post - about 5mm from one edge and 55mm from the other (central between the other two edges. See close-up at ). I think that two holes would have been accessible for use with the driver, but not the other two as the body of the driver would have got in the way. Maybe the driver could be used at an angle with a universal joint. Is that possible?

[Jeff Layman]

Out of interest I just compared some masonry bits with identically sized SDS bits (8, 10, and 12 mm). The masonry bits were Bosch and unbranded; the SDS were unbranded. The main difference was the flute shaping. The Bosch 8 and 10mm masonry bits were about a mm less in diameter than the equivalents SDS bits, but the unbranded masonry bits had the same diameter as the SDS bits. Other than that there was no difference. As far as I could tell, the Tungsten Carbide tips were of identical size in thickness and depth, so I don't think the SDS bit tips are any stronger than masonry bit tips.

[John Rumm]

Depends on the head of the fixing. Hex head for an Allen key, can be driven at an angle with a ball driver bit. Hex bolt head can be driven a bit off axis with a socket, and Pozidrive screws can also be driven a little off axis.

If you need to reduce the angle, then fitting an extension bit to the drill/driver/ID will usually help get at the fixing a bit "straighter"

(also worth noting that you don't have to drill the holes straight either - angling them will often help get an easier drive angle for the fixing, and will also make the fixings harder to pull out since they can be at a combination of angles that can't be pulled in any single direction).

[Tricky Dicky]

SDS drills in my opinion are much kinder on the drill bits. Using hammer dr ills the bits do tend to knacker with use. I bought an ELU SDS drill approx . 20+ years ago and bought 6, 7, & 8mm drills at the time, I still have tho se original bits which are drilling as good as when they were bought and my last house was a real test of machine, drill bits and man with walls made of over baked engineering bricks.

Richard

[John Rumm]

I did the same earlier, and noted that there were some differences between the Bosch multi-material and the SDS, although interestingly, less difference between the SDS and a conventional Masonry bit.

The Bosch have a slightly steeper angle at the tip, and the carbide is shaped with a flat sharp side on the leading edge. The SDS is bevelled on both leading and trailing edge. Shank on the SDS was slightly slimmer, and had a higher twist rate of flues. The Bosch design is presumably influenced by the need to have a sharp edge to give it the ability to cut wood / steel as well as masonry. The conventional masonry bit had a profile similar to the SDS - but obviously its useless in things other than masonry.

I also had a close look at one of my add on chucks, and noted that does have the full SDS+ flute pattern, so in theory could be hammered. I might have to find a masonry bit I don't care about and try and see what happens!

[Roger Mills]

Good idea! Be careful to get the length you need. The quoted length invariably includes the shank, so the the depth of hole you can drill is a lot (60mm?) shorter.

[Roger Mills]

No, but you could use an extension bar between impact driver and bit, so that the bit is at a slight angle to the bolt. That should work, especially if the bolts use torx bits, which many do.

[Jeff Layman]

Interesting. Unfortunately I don't have a multimaterial bit and SDS bit of the same size to compare. I guess it's probably because the masonry bit and SDS bit are essentially for the same purpose.

I assume Bosch spent a lot of R&D time on the cutting edge geometry to come up with the best compromise for masonry/metal/wood. The ability of those multimaterial bits to drill through rebar when drilling concrete is especially useful, as ordinary bits just come to a halt. I've just found what might be the next step - the SDS quick Multi-Purpose Drill Bit: . Not SDS Plus, though. They have been around for some time, but don't seem to be available from Screwfix (but are from Amazon). Have you ever used one of these?

What else would you be doing on a quiet Sunday in August?!

[Jeff Layman]

The heads of the bolts I had were standard hex. I did have to use extension bits anyway with the ratchet drive, as its head was too wide for the bolts at the narrow end.

[Jeff Layman]

Yes, I'd found that out (see my first post)! They quote 60mm, although the flutes go to 75 or 80mm. In practice, provided the hole is frequently cleared of dust, 100mm is possible, as there is room in the flutes for the last 20mm of created dust.

As noted in my latest reply to John Rumm, I've just come across SDS quick multipurpose drill bits. They seem ideal, except I'd need to buy a new drill!

[John Rumm]

No not tried those.

Well I was fixing some metal fence post brackets to the top of the wall, so needed to get the SDS out, so though while here, I can look at the bits :^)

[williamwright]

Have you noticed, though, how the hammer action is less effective with a heavy bit? I used to have to drill through brick and stone walls very often, and I found that if the material was hard and the hole was quite wide it was quicker to drill as far as possible with a short bit, then change to a longer one when necessary. The reduction in drilling efficiency when changing from, say a 12mm x 150mm bit to a 12mm x 400mm.

Also, I don't think the way a normal chuck holds the bit doesn't convey the percussive force very well, presumably due to slipping slightly. You know how a friction fixing that is seemingly very tight can be adjusted a fraction of a mm by use of a hammer? A normal chuck is only a friction fixing, longitudinally.

Bill

[jeff Layman]

I have no doubt you are right, although I've no experience of short vs long drill bits. It makes sense in terms of kinetic energy. The short drill will reach a higher hammer speed as it has less mass to accelerate, and as kinetic energy is proportional to the square of velocity, the shorter bit will have more destructive energy than the longer bit.

I suppose the rotation would be affected if the bit slipped in the chuck, but the bit would be touching the end of the chuck where it fits in the drill body and the hammering would not be any different. Also, some of the large diameter bits have smaller diameter shanks which fit in the chuck, and the larger-diameter shoulder rests on the outer end of the chuck, so again hammering would not be affected.

[Roger Hayter]

In the absence of any real understanding of the physics involved I am pretty sure intuitively that the second metal-to-metal junction will alter the dynamics of the hammer blow and make it much less effective. You can see this happening when you place something between something you are hammering and the hammer. I'm sure it's a real effect, though the maths is totally beyond me. I think sort of bouncing comes into it.

[Dave Liquorice]

Is this a normal "hammer" drill or SDS?

Unless the substrate is pretty soft (ordinary brick/block) "hammer" drills aren't very effective anyway.

With SDS if you don't apply enough pressure the bit just chatters in the hole, barely making any progress. With enough pressure you get that satisfying BRRRRUUPPP as the bit "engages" and you might be able to back the pressure off a little as the bit sinks into the material. In the former, the mass of the drill absorbs the energy of the impacts as it rattles up and down the hole. With the latter you have a Newtons Cradle effect and the impact energy just passes down the drill with it's mass having very little effect as it's barely moving.

Can't say I've noticed but then I'd normally start with a shorter and probably smaller bit to start the hole simply because it's easier to see the starting position and is easier to control. My long bits are

1000 mm though. B-)