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Drilling a Porcelain Sink

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  • Drilling a Porcelain Sink

    I may need to drill about a 1/2" hole through the deck of a porcelain kitchen sink. Here's the deal:
    Wife decided we needed to have filtered water, so bought an under-the-sink filter. It is designed to come up through the sink and have a skinny little faucet to dispense the water. Typically, these faucets come up through existing utility holes that can be plumbed for a flexible sprayer, or a disposal/dishwasher vent, or whatever the homeowner wants. Our problem is that our sink has only one of these utility holes, and it is taken by the vent. If I can't do something else about the vent, I need to drill a new hole.
    1. I'm not terribly clear about how the vent system works, so don't know if there is some other way I can plumb the things now connected to it. Right now, both the dishwasher and disposal have hoses connected to the vent. Can I do something different with these to free up the sink hole?
    2. If I'm stuck with keeping the vents plumbed as they are, does anyone have any suggestions/experience regarding drilling through the porcelain and cast iron beneath it? Obviously we need to minimize porcelain chipping, but probably need some different kind of bit to get through the cast. I've considered making up some kind of solid or annular bit and running it with abrasive to just grind through everything, but this would still require a pilot.
    If ignorance is bliss, why aren't there more happy people?

  • #2
    The vent doesn't have to be mounted to the sink deck. You could mount it someplace under the sink. That will free up the hole for other uses.

    Personally we like a liquid soap dispenser mounted in the sink deck.


    • #3
      You're on the right track. There are two tasks: getting through the porcelain glaze and then the cast iron.

      I've used hole saws with decent luck. Carbide is best, but HSS/bimetal works. You can drill a pilot hole for the hole saw first to prevent wandering. I've also made a plywood drilling jig matched to the OD of the hole saw to get it fixed where I wanted it.

      An abrasive slurry, careful use of a die grinder inside that plywood jig etc. will help get through the porcelain. A carbide hole saw will do it on its own as will a bimetal blade if you don't mind trashing it.

      When you're done, you'll still have some chipping. Be sure to prime and paint the cast iron to avoid rust under the glaze -- that can spread. Whatever you put in the hole should have enough of a flange to cover up what touched-up-chipping you end up with.


      • #4
        There is a series of hollow diamond bits, up to about one inch. They are not very expensive, and I expect that one of these, at low speed, with water lubrication, would march through the whole thing. It would be best to stick a piece of plywood, with a guide hole, to the sink with double sied tape.
        Duffy, Gatineau, Quebec


        • #5
          I drilled a 1/2 hole through an old fashioned porcelan outdoor lamp shade. I fist went through the porcelan with a Dremel and the quarter sized brown thin cut off wheels. I used that wheel to just eliminate the porcelan on both sides and then drilled the metal with a conventional bit. Just takes a little time and careful workmanship. BUT, it do work !
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          • #6
            Gee I thought this would be the perfect time for him to justify the purchase of a water jet.

            Never enough tools.


            • #7
              HF sells diamond hole saws for ceramic tile that should work after removing the porcelin like YOD suggested. Arter cleanly cutting through the porcelin a standard metal cutting hole saw should work to cut through the cast iron. I would cut through the porcelin on both sides before cutting through the cast iron.


              • #8
                A diamond drill will fly through that, but a 1/2" drill is getting near the small limit for ordinary ones. Use water for cooling and take care not to over-load it. Make a guide from card or thin timber to stop it skating on the porcelain.
                Peter - novice home machinist, modern motorcycle enthusiast.

                Denford Viceroy 280 Synchro (11 x 24)
                Herbert 0V adapted to R8 by 'Sir John'.
                Monarch 10EE 1942


                • #9
                  Another vote for diamond coated hole saws.
                  Cheap ($20 a set or something stupid), effective, should'nt excessively chip/damage anything, just use some clay or similar to build a 'dam' to hold the water (or do it outside with a water hose dribbleing over the drill site)
                  And idealy use a corded drill, your cordless batterys will likey die before the job is done :P
                  IE: you are going to be drilling for a long time to keep the stresses low to prevent chiping/etc. the diamonds can cut with very low pressure and perfer it that way, but it will take time.
                  And unless you have a continious water flow, keep the rpms (for the drill size) rather low to prevent overheating.
                  Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.