JOB: How do I drill a hole into a cast iron bath? I need 365Drills

[Deleted member 1779]

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[TD][h=1]How do I drill a hole in a cast iron bath? [/h] [TABLE="width: 660"]
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[TD] Dear 365-Drills, We are a contractor converting a National Lottery Heritage site and it contains this very heavy Drummonds Lomond cast iron bath that is difficult to move about.
We have made a mistake on the plumbing and want to fit a tap to the bath rather than through the wall. How do you drill a hole into a cast iron bath
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Brief - Contractor has to install a Drummonds Lomond cast iron bath into this project.
[SIZE=+1]How did we drill two holes into a bath ?[/SIZE]

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We are instructed to attend the project site and to drill TWO holes into a cast iron bath. ​

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Park up in the 365Drills executive limo. Nice spot under the tree...​

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[TD]The cast iron bath is still in its protective wrapper. We are asked not to disturb it too much. Contractor marks out the points for drilling. [/TD]
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[TD]First we have to grind out the enamel so that we can get down to the base metal. To do this use any one of our diamond cores. Use the side and then gently wear down the enamel until you see bare metal. Note if you try to drill through enamel with a normal drill at this stage you will simply slip. A normal drill cant bite the enamel. Think of it as if you were trying to drill a hole in a glass window. Would your drill bit work on a glass window? Answer no. So remove some material center hole for the pilot to get into the metal of the bath,[/TD]
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[TD]Once you have ground out a center part its time to drill a pilot hole through the bath. Do this with various size standard twist drills. Drill slowly. Open up the center hole.[/TD]
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[TD]Here you can see we have used a standard holesaw (metal) on a drill. Use it to slightly mark the enamel.[/TD]
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[TD]Look at the enamel above. You can see a scored ring from where we have used the metal carbide holesaw on the bath. Note: If you were to carry on drilling with the standard holesaw you would break the enamel and ruin the job. You now need to swap to a diamond core. The diamond core will be used to grind away the enamel carefully and to create the perfect drilling channel. [/TD]
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[TD]Take a yellow guide plate from the pack. In this instance the hole we want is 32mm for the tap so use a 35mm diamond core to overbore the hole[/TD]
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Use the diamond core to grind out a ring of enamel wider than the hole will be.
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[Deleted member 1779]

Re: JOB: How do I drill a hole into a cast iron bath? I need 365Drill

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[TD]Note you can see this is a very dirty grimy job. Its a mix of water and drill lube that is turning the iron black. Remove the yellow plate at this stage[/TD]
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[TD]You should now see a mucky puddle of cast iron filings, enamel, water and drill lube.[/TD]
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[TD]All washed and tided for you. What are we looking at? The center hole is ground out which is why its a bit chipped looking. Dont worry this is sacrificed so not a problem, Next we see where the diamond core has worn an outer ring and stated to create a channel to drill out the cast iron for the bath. We are not finished yet though.. We need to swap to a 32mm diamond core and open up the channel inside[/TD]
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[TD]Back to the drilling and we have now removed a lot of the internal enamel to make way for the metal holesaw to bite into the cast iron. If you do not have two diamond cores (in this case 35mm and 32mm) then you can CAREFULLY use the edge of the 35mm to wear off the enamel inside the circle. Note if you do not do this your metal holesaw will simply spin on the enamel and not get through to the metal below. You must clear a channel for it to work.[/TD]
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[TD]Wide shot of the cast iron bath for you. As you can see progress is slow but its doing well... This is a BIG bath,[/TD]
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[TD]To help the drilling you can also drill UNDERNEATH. Here the material is not enamel but a black overspray which the drill bites into easily. Question you might ask: Why dint I just drill the entire bath from below if the start is softer? Answer: First of all when you break out the enamel will shatter above. Also this is very physical work (hard work) and drilling upside down for so long will wear you out. Better drill from top down. But this will ease the drilling. It will help.[/TD]
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[TD]And we did it! Here is our slug, or core. You can see from my grimy fingers that this is very messy work and also that was a very very thick cast iron bath. Drilling even with the best equipment is time consuming and hard work. [/TD]
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[TD]Here is the result underneath. Looks clean and tidy. If you have any burs on snaggy bits nows the time to grab a file and just rasp them away. Nice and steady though. I know... I know... You want to see the finished result right? OK Here goes.[/TD]
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[TD]First peek at our finished hole "top side" and yes its looking a bit grubby. But is it perfect? Lets clean up.[/TD]
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[TD]Will grab a sponge, some washing up liquid. Lets clean the new holes so that you can see the final snaps.[/TD]
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[Deleted member 1779]

Re: JOB: How do I drill a hole into a cast iron bath? I need 365Drill

Will grab a sponge, some washing up liquid. Lets clean the new holes so that you can see the final snaps.

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[TD]OK from a distance looking nice and even. No chips or bangs. No cast iron bath in bits. Holes look tidy[/TD]
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[TD]Close up of them for you shown top down. All scrubbed up and looking bath like.[/TD]
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[TD] And this is all I dare pull off from the packing to show you the finished job. So we have a rather expensive bath made of cast iron with some lovely new holes drilled in situ and no sign of any chipped or flaked enamel. This should last a lifetime for the owners. Happy bathing people...[/TD]
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Job done and maybe time for a little paddle in the moat, or a wander round the grounds...​

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Diamond cores and advice available at 365Drills