Drilling overflow in old cast iron bath

[crashanova]

Incredibly, the old bath in my new flat has no overflow - there is simply nothing there, although thankfully the tub volume is so big that it takes for ever for the water to get anywhere near the top! I'd estimate the bath to be about 45-50 years old

I have seen posts regarding drilling tap holes in cast iron baths where a grit-edged hole saw was recommended.

My questions are:

Does the fact that my bath is rather old (or the fact that I'd be drilling into the side rather than the area intended for drilling, ie the horizontal surfaces) make any difference? I am just afraid of the bath being brittle and cracking, and wondering whether age heightens the risk.

Do you recommend approaching from the outside or the inside of the tub? I have to approach from the inside as the bath is in situ, so is this trickier?

Finally, is everyone of the same opinion that this can be done and that a gilt-edges hole saw is the best way? Is it too tricky for a lowly intermediate DIYer like me?


Many thanks in advance.

 

[Nige F]

Well, I wouldn`t bother ,because the overflows don`t take much water and what`s the point? if you leave the tap running the overflow won`t cope and if you`re in the bath, then just pop the plug to lower the water level and top up with more hot

 

[Diyisfun]

But the sound of running water, may alert you that the bath is running.
You can drill into cast iron, start with a small drill first. It may well falke the enamel but if you are carful you can do it.

 

[crashanova]

Cheers. Good point about the overflow not serving any worthwhile purpose (always thought that myself) but I have bought the bath waste overflow jobbie (techical term ) already and am going to go for it just for the sake of making this bath "normal" without having to sledge hammer it out and replace it.

I have a quite powerful variable speed hammer drill (with hammer off-switch) but it is not an SDS. All the grit-edged holesaws out there are for use with SDS-plus arbors (is this telling me something?? ). Is it much better to be using an SDS drill or can I get away with my one and keep searching for a grit-edged holesaw and arbor which is compatible with my 'conventional' chuck drill? Basically, how do you experts recommend I should and/or shouldn't proceed with this job in terms of correct tools?

I was thinking of investing in a 2nd hand good quakity SDS anyway but ideally I'd prefer to use what I've got.

And is it OK to use one of those holesaws with 'pilot' bit built-in to the arbor at the same time. What 'pilot' bit should I be buying for maximum success through thick, old cast iron?


Many thanks.

 

[Softus]

Cast iron, whilst brittle, isn't anywhere near as hard as tempered steel and doesn't put up much of a struggle against a drill. The high free carbon content makes it effectively self-lubricating.

As long as the drill bits are sharp you won't have any trouble - obviously you'll need the correct size of core drill, and one that can cut steel, but you don't have to use SDS for this.

 

[crashanova]

Cheers Softus.

This is all good news.

Like the bit about the free carbon content . It's good to get a grip of some of the science behind the procedures. Going to grab my old text books and see where your coming from. Thx.

 

[doitall]

One has to ask the question, why after 50 years ish you should even consider the job.

Buy a stand pipe plug if your that worried about flooding the place.

 

[Robotmannick]

I'd have to agree with doitall on this one. I can't really see any benefit in taking this project on.

Good luck if you try it. I don't expect you'll have too many problems, but IMO it will look a bit odd regardless of how you do it. I mean, how do you intend to finish off the edges of the hole so you're not left with potentially flakey edges? Even if you do manage to avoid the flakes, I still think the hole won't look right.

Just my opinion: feel free to ignore!

 

[Softus]

The hole doesn't need to look perfect - it's for an overflow and the edges will be concealed.

I find it bizarre that people are questioning the validity of doing this - would anyone seek to buy a bath without any overflow?

 

[crashanova]

Thanks to all.

The hole will indeed be concealed by the fitting I have bought, but I am also having the bath resurfaced which will seal and tidy up the hole's edges in any case.

By the way, nice one Softus - we unite in solidarity... it's a free world and I want my overflow!