Using a diamond core drill. any advice?

[saveasteading]

I am looking to take some core samples to see how thick a slab is . Then through the hardcore if it does that.

Planning to use a diamond core drill like this. Has anybody used one and can advise if it is straight forward or any tips?

The hire company doesn't seem to know how many holes a bit could manage. They are £30 each which sounds like a fairly ordinary bit.

It is £360 for a week, so it should be good.

[markc]

Diamond core drilling through a slab is really easy, you don’t need the rig unless you are doing large diameter holes. 50mm dia. By hand is no problem downward. Core bits have come down a lot in price but the quality does vary. Hilti bits have always been good.

[SteamyTea]

7 hours ago, saveasteading said:

They are £30 each which sounds like a fairly ordinary bit

Get these from B&Q for £27.41

https://www.diy.com/departments/42mm-x-150mm-long-diamond-core-drill-bit-1-2-bsp-thread-for-wet-or-dry-drilling-for-concrete-masonry-stone-brick-etc/5061037183703_BQ.prd

 

And one of these for £43.99

https://www.diy.com/departments/einhell-impact-drill-powerful-1000w-motor-13mm-drill-chuck-for-drilling-hammer-work-tc-id-1000-e/4006825587777_BQ.prd

[FuerteStu]

The reason they use a rig rather than a normal drill is the potential for it to lock up and kick. 

 

I've seen people seriously hurt themselves with core drilling. You need to keep your drill straight and a firm grip. Use water to minimise dust and cool the cutting.. Use a low speed. 

 

I great trick I was showed once was a bottle of water with a slit from a knife carved into it next to the hole. It trickle feeds next to your drill

[Alan Ambrose]

Also going gently with rpm & pressure and holding firmly & evenly & perpendicular to avoid sudden friction lock-ups / biting. Any anti-rotation leverage you can get is good.

 

i think torque required (& therefore kickback) is something like the square of diameter, so use the smallest diameter that will meet your needs.

[SteamyTea]

22 minutes ago, Alan Ambrose said:

i think torque required (& therefore kickback) is something like the square of diameter

It is force (N, mass x acceleration) at a distance (m, metre).

So

Torque = Nm

 

So basically, the longer the handle, the more torque can be applied.

 

Power (W, kW) is torque times angular velocity (degrees/time, though usually expressed as radians/s)

 

This is why a car engine gives maximum torque a little below the maximum power RPM and an electric car has maximum torque and power at 0 RPM.

 

As for safety, just don't put the drill between your legs (if your are male, females I will not comment on).

 

 

Edited April 4 by SteamyTea

[saveasteading]

That's good info thanks. Heart's will follow.

I'm thinking of 100mm cores to get a decent lump to examine and keep as samples.  Thus the torque will be a thing and the rig will keep it nicely in control for line and depth. 

I've seen this done by ' expert' survey companies before where there  have been  completely erroneous reports. So I'd want to be there, and then might as well diy it.

I'm wondering if the hardcore will be dense enough to come out in a core. Probably  not so l'll maybe use a normal sds below the concrete just to see how thick it is.

I'll see if i can get a second bit on a use  or return basis.

The best price so far is for a husqvarna rig which looks much the same as the hilti. Decent brand so should be OK.

My main concern is think is burning up bits. I've seen grinders go blunt very quickly. Also that bits and blades used to be charged per mm worn out. As above, perhaps that has been sorted technologically.

[SteamyTea]

6 minutes ago, saveasteading said:

I'm wondering if the hardcore will be dense enough to come out in a core. Probably  not

It is more usual to use an auger for the loose stuff.

 

Purely out if academic interest, what sort of tests are you going to do on the samples?

[Conor]

You might be better off with a con saw and cutting out a pit or three. Also, you'll most likely also need to dig pits at various points at the edges of the slab. What has your SE requested?

[saveasteading]

1 hour ago, SteamyTea said:

what sort of tests are you going to do on the samples?

A very simple one. How thick is it?

54 minutes ago, Conor said:

What has your SE requested?

It's me at present, doing a feasibility.  It takes forklifts and lorries and is visibly sound. Also,  i have the construction drawing but want to check it's as thick as drawn, and is visibly proper concrete without voids or junk in it.  Then I'll also see if the hardcore is a pile of loose bricks or properly compacted. Just duty of care stuff really.

[Alan Ambrose]

>>>

It is force (N, mass x acceleration) at a distance (m, metre).

So

Torque = Nm

 

So basically, the longer the handle, the more torque can be applied.

<<<

 

True, but the length of the diamond cutting edge (and hence friction) is also proportional to diameter, hence the square.

[SteamyTea]

3 minutes ago, Alan Ambrose said:

ength of the diamond cutting edge (and hence friction) is also proportional to diameter, hence the square

Isn't area the square.

Area =πr².

The circumference is proportional to π

[SteamyTea]

34 minutes ago, SteamyTea said:

circumference is proportional to π

That should be πr.

Mate came around to show me his cataract operation arrow on his head.

[SimonD]

19 hours ago, saveasteading said:

I am looking to take some core samples to see how thick a slab is . Then through the hardcore if it does that.

Planning to use a diamond core drill like this. Has anybody used one and can advise if it is straight forward or any tips?

The hire company doesn't seem to know how many holes a bit could manage. They are £30 each which sounds like a fairly ordinary bit.

It is £360 for a week, so it should be good.

 

 

I do 127mm cores fairly often, but by hand and without a rig. Just be patient, and like with metal, run the drill at a slow speed and let the diamonds do the cutting. Depending on how thick the slab is, bring the bit out every now and again to clear the dust. Just double check if the bits you're supplied with the drill or which you buy yourself are for wet, dry or suitable for either. I buy the Marcrist ones and they last pretty well.

 

Oh, and make sure your unit has a good clutch!

Edited April 4 by SimonD

[Gus Potter]

Here is a thing for all on BH to keep at the back of your mind when investigating say on old barn that you want to convert to a house.

 

Below is some of the things we consider as SE's. Remember that the SE works for you and will try every avenue to show what you have will be ok (provided you pay them for their time) for you.. but also for the person you sell the house to.. that is just about how all SE's start out.. as Civil Enginners.. the clue is in the word Civil.. we primarily work in the the public interest.. it's just you that picks up the tab.

 

You may want to reuse the existing barn concrete slab and build on top of it. It may well be that you have had farm machinery running over the top of it for years and you know in your heart it is ok.. but that is not enough for BC or an SE that is going to sign off to say it is going to last for another 50 years.. your mortgage lender may ask the same!

 

The concrete ages.. suffers from sulphate / ammonia attack, concrete carbonises and offers less protection to any embedded steel, the rebar becomes prone to corrosion. I'm not saying it is all gloom and doom but if it is going to perform for the next 50 years you need to get your ducks in a row.

 

Now I know that a lot of folk on BH are not a fan of Architects, SE's etc  that can offer advice.. but if it all goes wrong what then?

 

To recycle and old farm shed floor you need to know initially the thickness of the slab, how much the thickness varies,  if there is any mesh in it, what that mesh is and how heavily it is corroded. You also need to know if the mesh has just been flung in or if someone took a bit of care when they cast the old slab.

 

Now you could core one hole.. examine the sample and then say.. ok lets go to the design guidance.. which says.. sling your hook if you only have one sample. Minimum is three samples but from experienece the safety factors you need to then apply to only three samples often make a design unviable.

 

I've investigated industrial / farm building slabs and found that the most economic balance is to take 5 no 100mm diameter cores and see if you want to send them for testing. It's a good balance as with 5 cores you can get a handle on how well the slab was laid.. if the cores look crap or too variable then no point in spending the money on testing! You know early on if the concrete / workmanship is rubbish and can see if the mesh (if any) is all over the place.

 

If you get good looking cores then it is time to make hay! You get a feeling.. we have a good slab here .. lets take another two cores. Why you ask.. well the more cores we have the lower the probablity we have crap concrete and varying slab thickness etc.. it's to do with the maths / probabilty theory we use to assess the concrete slab strength..but the difference 5 and 7 cores could result in a 15- 20% increase in concrete strength.. which is a lot when we are in the no man's zone.. do we dig out or retain a massive floor?

 

To test another two cores may cost £200! and that could have a major impact on the fundamental design decisions which can cost thousands... maybe more.

 

 

 

 

 

 

 

 

 

 

 

 

 

[saveasteading]

9 hours ago, Gus Potter said:

as Civil Engineers.. the clue is in the word Civil.. we primarily work in the the public interest.. it's just you that picks up the tab

A QS once said to me, talking about Chartered Civil Engjneers.: "there are only 3 professions who vow to protect the public and world at large as a priority. Civil Engineers, doctors and nurses....and I'm not so sure about nurses."

[NailBiter]

On 04/04/2024 at 07:17, FuerteStu said:

The reason they use a rig rather than a normal drill is the potential for it to lock up and kick. 

 

I've seen people seriously hurt themselves with core drilling.

Some of the most recent SDS(+, max) drills have an electronic clutch system that will detect when this happens and reduce torque. There are also some mechanical clutches around.

https://support.dewalt.com/hc/en-us/articles/360012664938-What-is-the-DEWALT-E-Clutch-System

https://support.dewalt.com/hc/en-us/articles/360012593237-What-is-the-difference-between-Brake-and-Kickback-Brake-on-the-60V-MAX-DCG414

Edited April 7 by NailBiter

[saveasteading]

So far i saw a hilti jig listed at ' from £130' but the actual quote is £1200 for a week  minimum 'because it is a crosshire". Won't be going there.

Another national hirer says £320 per day or £420 a week, and i know they don't do discounts.

Now have a definite offer of £360 for a week. Will try one more that i'm told may beat that.

If I am doing 5 or 6 holes I'm prepared for this cost rather than a much more tiring  and vibrating time with a hand held. The control may save on blades too.

As @Gus Potter excellent essay above, the investment should be worthwhile in either saving construction cost or designing particularly to suit the situation.

How many slabs are uniformly as thick as designed? Not many. It's difficult and concrete is expensive.

How many fail because if this? Not many, as long as the quality is high.

Btw in no particular order these merchants are Travis P, Brandon, Alliance, HSS. The tools are Hilti or Husqvarna.

 

[SteamyTea]

33 minutes ago, saveasteading said:

concrete is expensive

Is it.

At around £100/m³ delivered it must been one of the cheapest materials there is.

You can buy standing timber, with the bark, at around £55/m³.  Once planed to size and stacked in Travis Perkins, it becomes about £2300/m³.

 

I am adding to this, as I am a bit bored this morning.

The embodied energy in concrete is around 2500 MJ/m³ (700 kWh), timber is 5100 MJ/m³ (1420 kWh), the embodied carbon is 360 kg/m³ and timber is 280 kg/m³.

Food for thought that is.

 

https://theconstructor.org/sustainability/embodied-energy-building-materials/567108/

Edited April 7 by SteamyTea

[joe90]

42 minutes ago, SteamyTea said:

The embodied energy in concrete is around 2500 MJ/m³

However, concrete should (proved by the romans) last a lot longer than timber so its embodied energy should be taken in context. Also even if dug up it can be used as hardcore so still usable. Timber can’t really be used as a “slab”.

[SteamyTea]

2 minutes ago, joe90 said:

However, concrete should (proved by the romans) last a lot longer than timber so its embodied energy should be taken in context. Also even if dug up it can be used as hardcore so still usable. Timber can’t really be used as a “slab”.

There are lots of material properties to take into account.

Concrete buildings never used to be much good in an earthquake, they are now though.

 

Main thing was, if I have my arithmetic right, is that concrete is not as bad as a lot of people think.

It has one big advantage over timber in that it can be cast into complicated shapes with very little waste.

[saveasteading]

With zero, or close to, waste. When I was ordering concrete for big civil engineering works I was allowed to round up by 1/2 m3 regardless of it being 5 or 50m3.  That allowed for what was left in the truck or on the shovels.

The washings were examined for excess, and then became hardcore . Quite right too.

Being short of concrete was a very serious matter.

[Alan Ambrose]

>>> the length of the diamond cutting edge (and hence friction) is also proportional to diameter, hence the square

 

I thought this, but forgot to write it, duh:

 

Imagine a core drill with one tooth (or diamond grain) which can be magically set at any radius. The torque required to rotate the bit (or equivalently the torque required to hold the drill) will be proportional to the set radius of the drill / cut.

 

Next, imagine you can magically add more teeth to fill the core drill to make it a full circle. The torque required to rotate the core drill will be proportional to the number of teeth. And the number of teeth will again be proportional to the radius.

 

So, the total torque for a normal core drill will be proportional to the radius squared.

 

Of course, there are other factors too. The above will be correct assuming we keep the downward pressure per tooth constant - which means we need to ramp the total bearing pressure linearly with radius. For conditions within a reasonable operating range, you can imagine that the torque required will also be a linear-ish function of the bearing pressure per tooth and also roughly proportional to drill rpm.

Edited April 8 by Alan Ambrose

[saveasteading]

On 07/04/2024 at 11:27, SteamyTea said:

At around £100/m³ delivered it must been one of the cheapest materials there is.

That's a good point.  But not many builders can calculate the volume accurately. Too much and it is dumped messily on site and a waste.

Too little an there are stop ends in a hurry, which cant be done sensibly with high tech structures.

Have you heard of 'plumbs' in mass pours tat seem to be  a bit short? 

Of course most builders add water which automatically increases the volume while weakening the structure.

 

A scary distant  memory has just appeared....calculating the volume to phone through for the final load of a huge pour, while the current load is still going in.

I'd forgotten my life had been so exciting.

[SteamyTea]

3 hours ago, saveasteading said:

Of course most builders add water which automatically increases the volume

Then let if overheat.

 

Back in '86, I did some composite plastic samples for material testing.

One of those samples was purposely made incorrectly (way to much hardener).  Popped them on the testing machines (tensile, compression, bending and vibration) and watched them explode.  The one that was purposely wrong failed very early, except for the hardness testing, it was way harder than the others, which accounts for the spectacular failure of the other tests.

(I did my apprenticeship in a company that made testing machines)