drilling cast iron?

(For those who've been following the thread "taps for roll-top ci baths?" with barely-contained excitement here is the sequel* ;-)
Can anyone offer any advice on drilling holes (about 20 - 25mm dia) in a cast iron bath for taps holes? Step drill? Hole saw?
* having drawn a blank on suitable taps costing less than an arm & a leg it occurs to me to blank off the existing holes in the vertical surface of the bath and drill new ones in the roll-top horizontal surface. Since the bath is going to be resurfaced (not enamelled) a spot of mesh + car-body-filler before the resurfacing should do the trick.
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John Stumbles wrote:

I've drilled cast iron before with bimetal hole saws with no problems - just take it slowly and it works fine.
--
Grunff

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can you not find something at a reclaim yard?
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it
the
bath
car-body-filler
Yes just use a hole saw take it slow do not use any cooling Cutting Past As Cast Iron is self Lubricating BigGuyUK
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Why not do it the old fashioned way and screw the taps to the wall instead? Far less work than carving CI up.
Regards, NT
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leg
of
the
As
Planning to put the bath in the middle of the room
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John Stumbles wrote:

How about mounting them on standpipes then? You can put many taps on threaded standpipes if you can deal with the floor mounting and water feed, of course a BSM may be more tricky - where does the showerhead stow when not in use? Two more possibilities to add to your list... BSM103 at http://www.chadder.com/public_html/accessories.html or more realistically, http://www.yor-appliances.co.uk/ecom/proddetail.php?prod=YAJASPIPES
--
Toby.

'One day son, all this will be finished'
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Visions of pipes coming down from the ceililng with taps on the end in mid air :) The taps would be the shower as well then
Regards, NT
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On Mon, 19 Jul 2004 23:44:16 +0100, John Stumbles wrote:

I have used a grit edged hole saw on a CI soil stack. It was not quick but it did the job. So that is likely your best bet but you'll need to make a 7mm (?) guide hole first. I'd try sacrificing a 3mm HSS bit first then brooch (sp?) out with a TiN coated HSS bit.
I've not tried this but I would think that a light weight diamond hole saws intended for glass/tiles should make a neat job. But they are 70 for _one_ bit + accessories extra. (26mm diam). Also you don't need the hole that good.
Like wise a heavy duty diamond core drill is about 30 + bits; but you'd have to make a 12mm hole first. (28mm diam - which I think is the size you want for clearance on 3/4" BSP)
Cobalt alloy holesaw - Apparently suitable for the hardest metals.???
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
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John Stumbles wrote:

For smaller holes the spear ended drills intended for tiles and ceramics also work well on cast. Might be a way of getting a pilot hole for something bigger...
--
Cheers,

John.

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John Stumbles wrote:

Aldi had some sets of those last week for 15. I didn't buy one as I hardly need them...

Lucky not to hit a hard bit in the iron.. if you do hit a hard patch (white iron) then that's it, unless you have special tools.
J.B.
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