Home Improvement → Advice for kitchen sink knockout

I need to make a hole in my kitchen sink, and I see there is a knockout that I can use. My question is how to punch out the knockout with out damaging the ceramic finish. Do I punch from the top or the bottom?

I tried it once. I bought a new sink instead.

But seriously, is this what you want to do:

»www.ridgidforum.com/foru ··· p=220496

And cover the (top) surface with a few layers of masking tape around the area you will drill. This will keep the metal filings from scratching up the surface. Always drill from the good side to avoid chipping. You can drill the pilot hole from the bottom, so its centered in the 'knockout' and then the larger holes from the top.

"Advice for kitchen sink knockout"

DON'T

Seriously, I would never try that on a glazed sink. What do you need the extra hole for? Why not just change out the faucet to gain the extra hole or two? Much cheaper than a new sink with the labor involved to replace it.

@whizkid3
Thanx for the tip.

@cableties
Yup, thats exactly the info I need, thanks for the link. Its a shame the drill kit costs as much as the Quick & Hot water dispenser that will use the new hole.

The worst that could happen is that I'd need to replace the sink, so I've got nothing to lose except the cost of the drill kit.

Maybe you can rent it at Home Depot?

If the cost is that high, and your not itching for a new tool, perhaps its cheaper to pay a one-time and have a plumber or counter top guy come in and put the hole in. A guarantee that no matter what, it'll eventually be right,

It's called knockout for a reason
Punch from the top.

Can he then send you the bill for a new sink? The knockout is there for use during manufacturing. They can easily knock out various holes, depending on the requirements for the particular model. Once the porcelain is applied, smacking it with a punch will get you shards of pretty white glass scattered around the kitchen.

Many moons ago at my old job, I used to have a knockout tool made by Greenlee that would be perfect for this application. Might cost less than the drill setup you found. Check out a place like Grainger's.

That's what I was trying to think of when I first saw this thread. The tool is used for putting holes in metal boxes.
What about a diamond tipped hole saw?

I still don't understand the need for the new hole. I just installed a very nice kitchen faucet which uses one hole for the spigot and one for the valve. The third is filled with a soap dispenser. Instead of installing the soap dispenser, put the new hot water dispenser there. It is an upgrade all around when looking at the pics the OP posted and there is no wasted expense for tools rarely needed, much less chance of breaking the sink and no exposed edge for rust to form on around the hole.

I agree with HarryH3 that the knockout is used in manufacturing before the finish is applied. I'm not saying that a new hole can't be done, but I don't understand the need when the present holes are underutilized.

There are currently 4 holes in the sink. Three of them are used by the spigot (center one for the spigot itself, two on either side covered by the spigot skirt that could have been used for separate hot and cold valves). The fourth hole, to the right of the spigot trio, has the valve, a lift-lever type.

The valve is separate from the spigot because the spigot is a lift-up version, which can be raised up about 10 inches to accomodate tall pots. I don't want to remove the skirt to expose the two other valve holes as then I'd have to find another way to cosmetically mount the spigot, not to mention that would make things non-symmetrical and leave an unused hole.

Much nicer to keep things symmetrical by putting in the hole to the left.

But then, I don't really have to justify my decision to you now, do I?

P.S. Thanx for the explanation of the 'knockout' usage.

I had to do a similar hole in our sink for a reverse osmosis water dispenser.

I applied a good coating of masking tape, drilled the pilot hole from below, then used a "cheap" $10 carbide-coated hole bit of the proper size from HomeDepot to finish the hole from the top. I had my daughter provide a continuous spritz of water over the work area as I drilled with my cordless drill. It took less that 30 seconds to get through the glazing and the steel. It was a piece of cake.

The alternative was a $60 diamond coated hole saw from Lowes. I figured I would try the cheap carbide-coated bit first. It worked fine.

Don't use a Greenlee 'Slug-Buster' or other brand hole-punch on this. They are made for going through metal boxes only, to create holes for electrical conduit & connectors. They will jam up with the porcelean finish, and also likely damage or even crack it severely. It has to be drilled. If you've ever experienced a jammed SlugBuster, you know what it means to wish it were 5PM on a Friday.