Drilling on a small piece, keeps cracking...

[smp50]

Hi. I'm trying to use one of these:

To cut a 25mm hole in a piece of tile (off the wall) that's only about 45-50mm wide. So there is not much tile on either side of the hole, and after three attempts the tile has cracked in two each time the drill comes close to finishing the hole. I'm going as slowly as I can, it takes about 10 minutes to cut through. Water cooled, in a hand drill (not a press, don't have one) and using minimum pressure.

Any ideas? Or is it just too small a piece of tile that's always going to fail? I'm using standard cheap square white tiles and there's a pipe I need to get around that's very close to a corner. Unfortunately the cracks are not neat enough to just line the tile back up on the wall, it's still quite visible.
Does anyone know the OD of cheap plastic pipe collars? If they'd extend across the whole width of the tile piece then they might cover the crack for me.

 

[Jackrae]

You might have more luck using one of these http://www.yourspares.co.uk/parts/ys160830/diamond-dust-holesaw--25mm-763622.aspx

 

[smp50]

You might have more luck using one of these http://www.yourspares.co.uk/parts/ys160830/diamond-dust-holesaw--25mm-763622.aspx[/QUOTE]

Yea, I got this because it was £2.99 and would do any hole size, whereas holesaws were quite expensive where I saw them. Are they much better, won't just run into the same problem?

 

[Jackrae]

Much gentler than a trepanning tool but you will need a guide plate to get them started. This is simply a piece of plastic between 1 and 2mm thick with, in your case a 25mm hole bored through. Place the plastic where you want the hole and fix it in place with some good sticky tape. You then use the holesaw through the guide hole until the diamond has cut its way into the face of the tile, after which it guides itself. Use lots of cooling water and use gentle pressure.

 

[alan333]

You could try drilling the hole then cutting the tile to your small size. It might break when cutting it, but it might not.

 

[smp50]

Ok, so on my 7th attempt I got it right. I hadn't been cutting on a whole tile because the hole is close to two edges anyway so I didn't think it would make a difference, but I suppose one less narrow border would help a bit and indeed it probably did.

I also started the hole from the back, then came over to the front once the pilot drill emerged.

A problem was that the tool, not being held completely level, broke through on part of the inscribed circle before other parts of the circle, so I'd be left with half of the material still in place and half gone, at which point the tool could no longer be used as there was nothing to guide it.

So at that stage I used a normal bit to chew off what remained, and a file at the end.

How draining, thank goodness I don't have to do any more.