core drilling

what size core drill do i need if i use a 110mm i worry the soil pipe being that size will jam and if i have to chop out mor it negates the benefit of using the core drill,should i opt for slightly bigger ?,also what do you rate as a good diamond core drill,i will need some for the 40mm wase as well,many thanks folks

IME if you can do the hole all from the same side you'll be ok. If you do half from one side and half from the other then any misalignment (which there almost certainly will be) will be a problem unless you have about 10mm of clearance. I always hire core drills, any that are affordable are made of cheese, total waste of money.

but what size core drill do i need if i use a 110mm i worry the soil pipe = being that size will jam and if i have to chop out mor it negates the benef= it of using the core drill,should i opt for slightly bigger ?,also what do = you rate as a good diamond core drill,i will need some for the 40mm wase as= well,many thanks folks

TCT core drills are far cheaper and perfectly effective.

NT

Last time I needed to do this, I just drilled a series of 8mm holes around the circumference, and then chiselled the centre out with an SDS drill ... slightly time-consuming, but cheap.

S'what I've always done. It ain't pretty, but it works.

Typical core drill sizes are 107mm, followed by 127mm ish. So you will need to use the larger one anyway. However, as a general rule, going a bit above the size you require is usually good practice since if its too close it can be difficult to get your pipe (or whatever) through.

Unless you are drilling lots of holes, you can usually get away with the TS/SF entry level ones (may be different if you need to go through engineering bricks!).

In the hands of most professionals core drilling ain't pretty. I'm reminded of soft nosed ammunition. The entry wound is neat...

Yup its fine for the pipe... two things I have noticed though, in the past not all of the makers did that size for some reason (although to be fair most of them do now), and if you need the collar of a coupling on a soil pipe to protrude into a wall at all (e.g. where a branch from the back of a soil pipe passes through a wall for a wc connection), then you probably need the 127mm.

(127mm is also handy if you need to do a boiler flue or extractor outlet when you only have access on the inside, since its large enough to allow a the sealing rubber flange to pass through the hole)

The purpose of doing this is to save scaffolding to a high level, but there must be some risk of spalling of the outside layer of the building structure. How do you deal with that from a H&S angle? Is it enough to have someone outside at ground level, keeping people clear?

It could be in some cases.

I find core drills are not too bad from a spalling point of view. The bulk of the core normally stays nicely in the drill. You might knock the plug of render off though I suppose. Not sure what would be done commercially though.

I got a set of Dronco core drill for what I thought was a reasonable price. Our local tool place were selling them for £120 so I thought i'd have a punt.

Same as these,