75ZT Community

Hopefully, somebody can help me with this problem.

I'm fitting some brackets for a venetian blind and I need to drill 6mm holes to accept the rawlplugs in masonry.

The problem is, the wall is eating my masonry drills They go in as far as the plaster and then just grind themselves away until the drill tip becomes rounded.

I thought maybe there was steel behind the plaster so tried HSS drill bit but that was destroyed as well

Can anybody tell me what sort of drill bits I need to get through this stuff please?

I honestly didn't think you could get masonry this tough.

If its a concrete type lintel over window that will give grief Paul.
I have generally found a decent(not trying to be rude)masonry Drill with a Hammer Drill action goes through with little effort, on our thick walls here.
I am sure others will possibly have better guidance for you. You could check not metal there with a metal detector if you have access to one?

It could be steel or concrete, you need to find out what type it is, do you have a small magnet or try looking at the dust that comes out and see if there any metal in there.

If it's a steel RSJ then you would need a good HSS drill, you won't need a raw plug as you could use some self tapper screws. You can always start with a small drill to make a pilot hole and then move up 1mm at at time.

If it's concrete then you need a good SDS drill and a nice new 5.5mm SDS drill bit.

Tis definitely concrete chaps.

What is SDS please Andy?

It's amazing how hard concrete and bricks can be after a few years. I've just had great problems cutting a new doorway through an old wall. The specialised masonry saw that I hired chewed its way through 4 carbide tipped blades in the process.

I expect that you've hit a hard pebble in the concrete and it will need breaking up with brute force.

raistlin wrote:Tis definitely concrete chaps.

What is SDS please Andy?

SDS hammer drills were introduced to the market in 1975 by Bosch. SDS stands for Special Direct System. They are similar to normal hammer drills, but have an improved hammer action that allows more powerful hammer blows. You will also need SDS drill bits that are specifically designed for SDS hammer drills, these improve safety by reducing slips, and are more robust than regular bits.

Normal hammer drills need to move the whole drill chuck to apply the hammer action. An SDS drill will allow the bit to move inside the chuck, allowing power to be directed more accurately and efficiently, which results in better performance drilling through substances such as concrete.

What are the benefits of an SDS drill over a normal Hammer Drill?
Drilling hard masonry, concrete and bricks are where the SDS hammer drill excels over normal hammer drills, drilling through substances up to 90% quicker than conventional hammer drills. If you carryout these sorts of tasks regularly throughout the day, it is obvious how much quicker you will be able to complete your work with an SDS drill.

Drilling modes
Drill Only
Normal drill without hammer action, maximum speed is typically slower at 1500RPM, and torque is higher than normal drills.

Hammer Only
Also called “roto stop”. You can fit a range of SDS chisel bits and use the drill like a micro concrete breaker. Ideal for light demolition, removing tiles, bricks, and creating socket cut ins or cable runs. Not all products will have this mode.

Drill and Hammer
Drill mode with the hammer action. SDS hammer drills can be quieter than conventional SDS hammer drills, despite the extra performance.

Beneficial Features
Safety clutches improve safety by cutting the power to the drill bit if jams in the substance being drilled. Without this, if the bit does jam, the drill could spin out of your grip and cause harm to your wrist/arm, knock you off a ladder, damage the substance or hurt bystanders. Mid range drills and up will have this feature, it is highly recommended.

2kg is an ideal weight for a drill that is used regularly. 4kg+ drills will be ok if you only use them occasionally, but long periods of use will be harder to work with. Low end budget drills tend to be heavier.

Decent speed control will allow you to be more careful entering and exiting substances.

Rotation lock allows you to lock the rotation of the drill, so that if you want to chisel into substances, it will not rotate. This is essential if you want to use the drill in hammer mode to chisel accurately.

Note
Because of the increased power you will have using an SDS hammer drill, be careful when drilling as you could remove large sections of the wall when the SDS drill hammers its way out. Drilling small pilot holes and taking care would solve this.

SDS drills will give the maximum drill bit diameter in the title, such as 1 Inch, or 1 1/8 inch. Bigger drill bit diameters will fit, but will be underpowered.

With concrete lintels, occasionally the aggregate will contain granite pebbles, if you are unlucky enough to hit one your drill bit will just burn out. Andys suggestion of a good SDS drill and bit with hammer will smash the pebble.

Hmm... £15 for a venetian blind... god knows how much for a drill

I've tried several test drillings around the area though so guess it's not just an unlucky strike

Alternatively, anybody reasonably local to me with an SDS drill I can borrow please?

Paul, you could borrow mine. I can bring it Sunday.

I have to say, it does tend to make holes wehere other drills struggle.

They are also great because they usually have a rotary stop function, which means they can have chisel bits fitted and are great for taking plaster off walls and breaking up those gobs of concrete at the bottom of rotten fenceposts.

Paul. The plasterwork should be an inch plus thick yes? It may well be that a shorter screw / rawlplug will be adequate for a blind...just depends how much tugging the mechanism will be subjected to?

@Duncan:

Yes please mate Do you perchance have SDS drills of 5 to 7mm?

@Carl:

The plaster is approx 9mm thick Carl Nothing to support the weight / stress.

Another great tid-bit of information there! A car forum that also happens to be a drill forum

SpongeBob wrote:A car forum that also happens to be a drill forum

... as long as you don't use one of these SDS drills while working on a car.

Have a look on Screwfix site - they sell some cheap SDS drills and they work. Some also come with a conventional chuck that you can fit.

And yes, 90% quicker is possible.

The chisel action is also useful.

If your looking to buy a SDS drill don't forget EBay,

This year I have brought a 2nd hand Dewalt 240v SDS drill with case in good condition for £35 which I use nearly everyday at work and I also got a good Bosch 110v drill with case for £25. There are deals to be had if you not in a great rush to buy.

Tried Duncan's SDS drill when I got home after the nano-meet. All holes drilled perfectly in less than 5 minutes No hesitation, deviation or the other thing

I still have some Argos vouchers left from Christmas so Bosch PBH 2900 now ordered

Thanks for the help chaps

Glad to hear it,

I was worried I might have to come up with my Hilti TE5



Not a picture of my drill but the same make/model

Ooh those Hilti T5's are the business. I hope you were going to remember your 13amp adapter.