Concrete drilling problems.

Gareth

Veteran
I am in desperate need of advice regarding drilling a concrete floor.

My all singing all, dancing American made tube bender eventually arrived after being held at Customs for nearly a month, and I now need to get it fixed to the floor. The fixings that I am using are 10 mm diameter floor bolts that require a 16 mm diameter hole X 90 mm deep drilling in the floor .... .... .... I am using a standard 1/2 chuck percussion drill, and all I am doing is burning out the drill bits. ... and so far I've not achieved to drill one full hole for a bolt.

I have considered hiring a "wet" diamond core drilling machine, but none of the local hire companies seem to have 16 mm diamond core bits available.

If needs be I can increase the size of the bolts up to either 12 mm or 16 mm dia bolts, and I know that a 12 mm bolt requires a 20 mm drill bit, but I am unsure about the 16 mm dia bolts.

Any advice about drilling concrete and installing floor bolts will be greatly received, as I must have this tube bender bolted down and in use as soon as possible due to the appalling delay caused by the Customs and Revenue service eating into my production and delivery schedules.
 

xpc316e

Senior Member
You need a drill that has a pneumatically operated percussion facility. They used to be v. expensive (I paid £160 for mine, years ago), but are now more affordable. They use special SDS drill bits and will just sail through concrete. I bought mine as I was fitting blinds to reinforced concrete lintels, and it is still giving good service. I'd hire one for a few hours if I were you.

I'd then drill a ring of smaller holes with a 6mm bit, or similar, and break out the concrete that's left with a chisel.
 

Kestevan

Last of the Summer Winos
Location
Holmfirth.
Failing that, start with a much smaller drill bit, drill a pilot hole and then enlarge it. Work up in 2mm steps to the right size.

When drilling, use an even pressure, and a slow drill speed. You don't want to overheat the bit. Stop after every couple of cm and let the bit cool, try and keep the hole free of debris and take your time.
 

Zoiders

New Member
You need an SDS plus drill, a big un like a Makita Supermak to run a 16mm bit.

It is not however the SDS drill bit tip it's self that makes the difference, the tip is no different to a non SDS masonry bit.

SDS drills have a hammer action that reciprocates through about 10-12mm in use, the two splines with closed ends on the shank of the bit are part of the detent system that allows the drill bit to move back and forth, the ends are closed to retain the bit.

The impact action has a longer stroke but more importantly it lifts the tip of the drill bit away from the drilling surface for longer as you drill, it's in effect just touching the drill bit to the material every so many revolutions. This means the tip does not ever heat - this is the most important feature of SDS, the slightly longer impact stroke and the lack of over heating helps to retain the hardness of the bit and break up any agregate contained in the concrete.

I thought I would clear that up as the idea that SDS drills work because the bit is simply harder is incorrect, I also would not want someone to plug an SDS bit into a normal jawed chuck, it will work in a fashion but no differently to any other drill bit - it would still over heat.
 

gbb

Legendary Member
Location
Peterborough
You really need an SDS drill at the least, readily available for hire from tool hire outlets. Even the cordless (18 or 24v) or very effective.
Is it possible youve hit steel re-inforcing bars in the concrete ? They make things almost impossible. Re-siting your tube bender will be an easier option if that were the case.

Your fixings sound like Rawlbolts. The problem with them is accurately drilling the holes, then you have to place the equipment on the anchors in the floor and hope all 4 (i assume) bolts will be in the right position. Often, if one fixing is a few mm out, you'll struggle to get the bolts in.

Throughbolts are a much easier but almost as effective option. They allow you to drill while the equipment is in situ, then hammer the bolts into the floor (while the equipment is still in situ) then tighten up the nuts. Maybe not as strong as Rawlbolts, but still very very effective.

Another benefit is that say a 12mm throughbolt only need a 12mm hole, and so on. Your not trying to drill whacking great holes, which of course is more difficult.

Hiring an SDS is almost a neccessity. Not too expensive for a days hire. The job should take an hour at the most.
 

Zoiders

New Member
I can't see the re-inforcing fabric sheet being that close to the surface of the floor if it's a sealed comercial floor in a work unit. It wil be pretty deep below the final screed as they know that racking and machine tools are going to be bolted down to it.

For such a big bit of kit and to offer that last bit of wriggle room and adjustment when bolting it down I would go for resin anchors instead of expanding.
 

slowmotion

Quite dreadful
Location
lost somewhere
As others have said, hire an SDS Plus drill. In order to get the hole placed accurately, start with a small diameter bit, say 6-8 mm, and then enlarge it progressively. If you start with a 16mm one, the bit will almost certainly wander. As regards re-bars/mesh in the floor, you will have problems if you hit one. No way will you get through one with a concrete bit. If you are drilling into a domestic garage floor, I would guess it wouldn't have reinforcement. If it is a light industrial unit, on the ground floor, it might have mesh on a 150mm square grid.

Good luck.
 

longers

Veteran
How much vibration or kick back do you get from the SDS drills?
10-12mm action sounds like a lot but I've never used one, I'm just being nosey.
 

slowmotion

Quite dreadful
Location
lost somewhere
Cross-post by me, sorry! Yes, resin anchors also have the advantage of not stressing the concrete in tension, unlike expanding fixings. This means you can place them very close together without cracking the concrete.
 

slowmotion

Quite dreadful
Location
lost somewhere
longers said:
How much vibration or kick back do you get from the SDS drills?
10-12mm action sounds like a lot but I've never used one, I'm just being nosey.
Mine is a Bosch Multidrill and it has very little vibration. Not at all like a road drill.
 

Zoiders

New Member
slowmotion said:
Mine is a Bosch Multidrill and it has very little vibration. Not at all like a road drill.
Bosch blue ones have no direct impingment between the cam driving the hammer action and the drill bit. A piston creates an air cushion between the two ends of the drive train. It's like an air shock sus fork in a way, force is still transmitted but it's smoothed out and damped.

They don't kick back any more than normal hammer drills, brute force is not how they work.
 

longers

Veteran
Thanks, I've seen them being used and they've not looked like hardwork.
I just need to think of something that needs drilling.
 

gbb

Legendary Member
Location
Peterborough
The more i think about it, as long as the equipment is not prone to being hit by forklifts or anything ( i dont know your circumstances there)..i'd go throughbolt every time.
Ive fixed so many items, barriers, machinery, fences, rails, you name it, ive lost count.
Rawlbolts, having a larger fixing area are better if the equipment is prone to being hit heavily or often...throughbolts are infinately easier to use, but dont resist that regular impact by other objects as well as rawlbolts.
If your equipment is not prone to be hit by anything on a regular basis...throughbolt every time.

The other benefit is, if you do hit a piece of steel re-inforcing, you sometimes can get through it with a smaller bit you'd use with a through bolt, as opposed to a large bit with a Rawlbolt, which you stand no chance with.
(edited to expand on that....sometimes when you do hit steel bars, you can sometimes still complete the hole. I assume the drillbit works its way round the bar, rather than drills through it)

It does sound shallow to have hit steel re-inforcing, but never assume anything. You'd be surprised what you find sometimes.

Shame really, if you were local, i have all the equipment and fixings, i'd give you a hand. It really is straight forward with the right gear.

I'd expect the drilling to take a minute or three per hole with an SDS. I cant sing their praises enough.
 

leyton condor

Über Member
Location
London
You should be able to hire a SDS drill from a hire shop, or Argos do one for £29.99.
It probably won't last for ever but you should be able to do that one job with it.
 
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