+1 to find or make hardware that fits. Does anyone know a machinist?
Don't damage the porcelain. Paint AIN'T as durable. Machine the brass instead if you don't want to see rust years from now.
This may be of interest How do I drill a hole into a cast iron bath? Drilling baths.
As to coating in the hole I was told that its essential to use some sort of rust killer followed by a high build coating system with primer rather than a simple paint. Primer is really thin so I guess its more like an etch primer. When the coating system is fully hardened, takes a couple of days I believe, usual slatherings of silcone on assembly to really seal everything. Guy who told me decided it was too much trouble to have done so he got a new bath.
I have done this job using the method recomended by Jim. As others have suggested plug the hole first with a wooden pug to serve as a center guide for the pilot drill. Then I hve used a very dull hole saw and valve grinding compound. You need just enough pressure to keep the grinding compound moving under the saw. lift the saw often and use a small brush to feed the compound into the kerf. It is slow but will do a very neat job of the hole with no chipping of the surface finish. The reason for the dull hole saw is that the teeth do not do the cutting but are there to move the grinding compound and the more surface area in contact the faster the grinding compound will cut
Originally Posted by jim rozen
I bet somewhere out there on the internet there is a collection of guys, who would probably know someone who could make some nice 303 stainless adapters that could be brushed to give a nice finish in the tub.
As to the pilot question, Starrett make a special holesaw arbor they call their "oops" arbor. It allows you to mount two saws with the smaller one somewhat ahead of the larger - which makes the smaller saw act as a pilot.
Use a continuous diamond as mentioned above with a wood hole pilot and Absolutely drill from the top. It will break/chip if done from the bottom. Slow and Wet....
Thanks for all the replies.
Here are a couple of photos of the sink in question:
there was a thread on making a type of hole saw - for making the round viewing glass for gauges - it was on this site some time back - may be if you still wish have a look at for it -
Test a plasma cutter on an old fixture....
No sink expert, but looking at my 30 year old sink...
If you cut thru the Porcelain with a cast iron base, you are creating a RAW edge..
Said raw edge WILL, eventually get water under it, LIFTING porcelain from the cast iron as it rusts.....
Make a NEW fitting, to adapt to modern drain plumbing...
I've been drilling with diamonds for more than 20 years and I don't think I'd like to attempt that. Certainly not without the customer accepting all the risk.
Originally Posted by The real Leigh
Stroll down Lockhart Road (the porcelain and metals plumbing side, not the 'meat' plumbing side), or over on Mong Kok (same again w/r adjacent 'redlight' district) and I'd have the parts.
Originally Posted by magneticanomaly
Hard to name a fixture maker in Europe, Asia, or the US that does not have their wares on display here, and the range of fittings covers it all.
Should be just as easy to order wot already fits online. Dirt-simple to adapt supply-side, just as easy on DWV.
US 'Big Box' stores have a wide variety of 'appearance' choices, but not even a small fraction of the mechanical side choices in global use.
Don't do it! Find the correct parts. The UK is a great source for antique parts.
There is no doubt that the hole can be enlarged using one of the several slow and wet abrasive methods mentioned above. But George's observation is key here. The underlying cast iron will rust in between a few months to few years and will discolor the sink around the fitting. The porcelain in the sink currently continues right on down the existing hole. If you cut the hole and then stick in drain fixture I think it is almost certain to rust. As second significant drawback to cutting is the edges of the fixture will stand proud of the sink bottom. I would be willing to bet the original fixture did not stand proud of the bottom. Does that matter---yes, the customer wants a first class job here not a work around.
Originally Posted by gwilson
Two reasons to either find a replacement (very likely could be done) or machine a new one.