core drills

Hi,

I wanted to put an extractor fan in our cloakroom. I've never understood why they are called cloakrooms because I've never seen any coats in it!

So I have bought a cheap TCT core drill from Tool Station. It's made by silverline and I don't know what you think of it but for occasional DIY use, I am hoping it will be fine.

I wonder why they are called core drills when they drill through masonry but hole saws when they go through wood?

Anyhow, there are no instructions included so please can you help? It seems obvious that the core screws on to the arbour. I also bought a guide bit. Are these essential? I would think they are as they would help you keep a straight line and prevent the drill from catching?

The bit does not have a thread, at least not on the arbour end! How does it stay in place? I pushed it in but it kept falling out. Am I supposed to encourage it with a hammer or a sharp tap against the wall?

I know I have to spin it as slowly as possible (its 110mm diameter) with a drill with a clutch but I am unsure whether to use hammer action or not?

I presume it will only drill as deep as the core, so at that point do I stop drilling and chisel the core out before continuing?

I realise I should drill a small hole through the wall to mark the centre and work inwards from both sides, meeting in the middle.

Thanks in advance.

Probably because you tend to drill much deeper holes in masonry...

The guide bit is essential for starting off. Once you have started cutting your core you can remove the guide bit.

It will be a morse taper fitting. protect the tip with a bit of scrap wood and tap it with a hammer.

You probably want to spin it at 1000 rpm ish. That is often close to max speed on a SDS machine.

The TCT bits you can use hammer on, the diamond ones you can't

Yup. SDS chisel will make it easy. The longer ones will do a whole brick at a time which makes it easy as you do the two leaves of the wall in two hits.

No real need to go in from both sides - there is no real exit wound with a core drill (with a TCT one, turn off hammer for the last bit). Also if you drill from both sides you will end up with a core that is not in perfect alignment, Which can make putting a sleeving tube through it difficult.