SDS Core Bit - 110mm - hammer or just rotation?

[bookieb]

Hi All,

I'm fitting a 4" extractor fan through a solid block wall. Rather than faff around with drilling lots of parallel holes, then attempting to chisel out the middle (as I've done previously), I decided to lash out and buy a suitable core bit.

It's an SDS TCD core bit, with a smaller guide bit in the middle.

110mm outside diameter.

Should I use hammer+rotate with this bit, or just let it "grind" on rotate only?

Planning to start on the inside, cut to the 75mm depth the bit allows, drill through the guide bit hole to find the spot outside, then drill back in from outside. If this doesn't join up, and I don't think it will, I'll chisel out the centre of the cut, and go again. Does that sound reasonable?

On the inside, the wall has been faced with 50mm insulated dry lining board, but not yet taped or skimmed. I'll have to cut through that first before reaching the inside face of the block. Any reason not to use the core bit at slow speed and no hammer to make that cut first?

Any other advice or tips much appreciated on using this bit much appreciated.

Regards,

bookieb.

[Andrew Mawson]

allows,

drill

lining

Drill all the way through the wall with an sds drill of the drill guide diameter, then drill from both sides with the 110mm core drill, that way you get a neat hole on both sides of the wall that does line up. If your core drill is diamond impregnated then it just needs to rotate, but if it has tungsten carbide teeth then it needs to hammer as well.

AWEM

[Tabby]

no, drill all the way from one side. Its normally easy to knock the central masonry plug out once you've drilled around it.

NT

[John Rumm]

Depends on how long your arbour is - on thick walls the drill won't fit through the 4" hole ;-)

[ARWadsworth]

It depends how high up on the outside wall the hole is!

[The Medway Handyman]

Errrm. My TCT core drill set says definately no hammer in the destructions & thats how I've always used it.

[Tabby]

I got the extension bit with mine. And the hex shanked arbour as well

- dont try using that unless you have to.

NT

[John Rumm]

The normal 6 or 8" arbour is ok on the diamond cores by itself, because they are usually 6" long themselves. I normally drill out with 8mm bit first to set the position, but then core back from the outside to keep most of the mess there! (unless its too far up that is)

[bookieb]

Thanks to all who replied.

Will take it easy and keep the pressure light and speed moderate.

I'll try no hammer first - no great hurry anyway, and I'd sooner take a bit longer than risk a bad jam.

If no/very limited progress, will try hammer.

Regards,

bookieb,

[Andrew Gabriel]

Always try without hammer action first. If the brick is soft and cuts easily, you get a better cut, and you may avoid problems some bricks have when exposed to SDS hammer, where the whole brick instantly disintegrates. Don't use hammer on thermal blocks either, or to cut through the plaster layer.

A friend had two nasty incidents doing this with a cheap SDS with no saftey clutch. First time the core jammed, the drill spun a part turn before the drill body hit the adjacent wall, and then it wound up the arbor like it was made of plasticine. Next time, the drill body spun, whacked him on the chin, and resulted in a visit to A&E and a few stiches.