127mm core drilling error, help please

[MikeT]

I have a few holes to drill and so does a friend so we bought a 127mm x

150 diamond core drill between us, it came with a 200mm sds+ core drill arbor and a 10mm x 200mm tapered guide drill.

I bought a Titan 1250watt sds+ drill with safety clutch from Screwfix and today attempted my first hole through single skin brick.

I first fitted the pilot drill to the arbor and drilled that hole right through, then fitted the 127mm core to the arbor and attempted to start drilling.

What a mess, it was just like trying to drill the core out without a guide drill fitted at all. The 10mm bit only sticks out 15mm in front of the core and after just a few seconds that had opened the pilot hole up so far that the likelyhood of ever getting the core to stay in one circle is remote to say the least.

What did I do wrong?

My thoughts are that the pilot drill as a guide with just 15mm protruding is just not enough to guide the core.

I understand that once the core is into the brick by 20mm or so the guide is probably best removed, but how to get to that stage!

Having tried it I would have thought a 13mm x 250mm or more guide drill would be the ideal to keep everything going neatly until the core is deep enough.

Suggestions please.

[dom]

Never used such a large core drill, but with a 45mm I always go striaght in with guide bit and core as one. I can't see why you wanted to pilot the guide bit right through first.

[MikeT]

The plan was that I could then cut from either side if one prooved too difficult (just above a shelf) as it was a big lump of brick flew out of the outside so I had nothing left there to guide the drill core anyway.

I have used plenty of metal cutting hole saws up to 75mm and know that the guide drill is paramount to cutting a clean hole in metal but this is my first attempt at brick cutting.

[Jim Alexander]

Did the instructions say to make a pilot hole right through? Done a few of these, too long ago to remember the exact procedure but checking the Marcrist support page it says drill with the pilot drill until the core is 5mm into the material then remove the pilot drill. Maybe that is the problem.

Jim A

[Stephen Dawson]

My Hilti DD rig has a clip on pilot bit, which starts the hole to a depth of between 3-4mm. Then through the wall like a knife thru buttER

Steve

[MikeT]

Be nice to have got that far in Jim ;)

With it all thrashing about all I have done is make a big mess on the brick surface with the core cutter tips. There were no instructions with it but I would have remover the pilot if I ever got far enough into the brick to do so.

The only thing I can think to do now to recover the job is to either buy a 13 x 250mm taper drill and use that to get a good clean pilot hole to guide the core in, or grind down an sds shanked 13mm drill I have here to fit the arbor and use that as above. 3rd alternative would be a bit of 10mm silver steel rod and grind a taper on that to fit the arbor to get the core started clean.

Another slightly worrying thing is the safety clutch, no mention of it in the sds+ drill manual, but is was spec'd on Screwfix's discription. I emailed screwfix and they replied a day later to say they had asked the manufacturers and yes it did have a clutch, I guess I will find out if it tries to snatch on me.

[Jim Alexander]

I guess there is no easy way to suggest his but you did have hammer off, didn't you?

Jim A

[dom]

Try a wooden plug in the pilot hole. You'll be surprised how an sds bit is able to push into wood nicely.

[MikeT]

Yes Jim I did ;) I did read some other instructions on line about using core drills even though mine didnt come with any.

Mike.

[Steve Walker]

Maybe bang a piece of scrap metal tubing into the pilot hole to make a discardable liner?

[John Rumm]

Two reasons for drilling a pilot: it lets you drill from both sides and still have a fair hope of meeting in the middle, and it also *can* make drilling quicker in some materials.

(I have found dome types of brick that cut rapidly with the diamond of the core bit, but take forever to drill without hammer action on the drill)

[John Rumm]

For anything but the simplest single skin walls there is no "if" about it IME!

[Osprey]

I drilled a couple of similar large holes, same method as you , but I kept the drill bit in place until core bit was at least 30mm into brick. If you have tct then hammer on ... diamond then hammer off. Slow, with even pressure.

Now to get you going again ... why not fill the hole with a rapid hardening compound, plenty on sale in B&Q etc, or mix brick dust with cement and grout fill hole and leaver over night. Then start again.

[Mathew Newton]

I'm no core drilling expert however when I hired a 150mm core drill it came with a pilot drill bit AND a *smooth* guide bit. Hence, I drilled right through with the pilot drill bit and then used the core drill along with the smooth guide bit to do the biggie. The smooth guide bit obviously didn't do any further damage to the pilot hole hence the whole thing went through cleanly...

Mathew

[Mathew Newton]

Forgot to mention... here I am getting ready to do the drilling...

(Yeah I know what you're thinking - the bit does look somewhat on the large side)

[Guy King]

The message from "Osprey" contains these words:

I found that water helps. The slurry seems to act as further abrasive.

[John Stumbles]

Because it's often useful to be able to check where the hole will (or should) come out.

It can be a bit of a pain to get the core drill started if the surface layer (plaster or whatever) is too flakey to guide the centre drill in. I suppose a longer centre drill or some sort of rod might be nice, but I usually find I can get the main core drill cutting to the point it self-stabilises by carefully offering up the rotating core drill to the wall slightly off-axis so that just one part of the rim starts to cut at first, and then straightening it out as it cuts deeper.

Industrial grade language may also help :-)

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Mathew Newton" saying something like:

[shaun]

Not teaching you to suck eggs but be very careful until you find out.

A pal of mine ended up in A&E when he found out his cheap SDS didn't have a clutch. He was up a (short) ladder drilling a core, the core bit snagged and the drill swung round at full speed smacking him square in the face. He was very lucky it didn't shatter his cheek / eye socket - the broken nose was seen as a lucky escape.

That particular drill is now consigned to chiselling only....

[TheScullster]

"Mathew Newton" wrote

Bang on. Have done a couple of similar jobs recently but had forgotten about the solid centre guide. Going through breeze was OK, but the external brick leaf took forever (guess that's the price you pay for being a light weight office boy instead of the rufty-tufty building site dweller).

Phil