How to drill a hole in the bottom of a stainless steel mixing bowl?

I would like to drill a hole into he bottom of a 3 quart stainless steel mixing bowl in order to insert a 1/2" brass needle drain cock (and then secure the valve to hold liquid).  How do I measure the diameter of the valve so I use the correct drill bit?  How do I get the hole centered.? How do I keep the pot stationary? The bowl is thin, how do i keep the bit from ripping the metal?

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pippi1133 years ago

i realize that this post is quite old but i am making a bar sink out of stainless steel bowl. we drilled the hole but can't seem to find a drain that sits (semi) flush to the bottom of the bowl....any advice?? thanks in advance!!

The easiest and most accurate way to measure the valve would be to use a dial caliper or perhaps a set of dividers. But, you could probably get close enough using a ruler.

An easy way to determine the center of the bowl would be to trace the circumference of the bowl onto a piece of paper. Then draw a square using the same dimension as the diameter of the bowl for each side. The square should touch the the circle at one point on each side. A good guide for this would be a framing square or a T-square if you have one. Now draw a diagonal line corner to corner on the square. The intersection of the lines should be the center of the circle. Now transfer this template to the bottom of the bowl.

To secure the bowl for drilling, ( I assume you're going to use a hand drill) place the bowl at the corner of your work bench or table so that it touches the 2 tabled edges. Then use C-clamps on 2 sides to fix the bowl in place.

To drill your hole you will need a sharp bit. Since it is stainless steel (this metal is very hard) I would use a cobalt tipped drill bit. If you don't have one a high speed steel bit will work, but it will take longer and you will need to take it slow and use a lot of cutting oil. The first thing you will need to do is to mark the center of you hole with a sharp punch. Place the punch on you center mark and give it a firm whack with a hammer. If you you don't have a center punch, a nail or a philips head screw driver will do in a pinch. You need to do this to leave a small dimple in the metal to catch the drill bit and prevent it from skating when you start to drill. Once you have punched your center point you can start the drilling process. You should be wearing gloves and eye protection before you start. Place the tip of the drill bit on your mark and start the drill. Apply steady firm downward pressure to the drill. Try to keep it as straight as possible. Take it slowly and apply some cutting oil to the cutting surface of the drill bit as you work. Cutting oil, 3-in-One oil, motor oil, or even WD-40 will work. The main points are to keep the drill straight, drill slowly, and don't push too hard once the bit breaks through the bowl it might tend to bind up. Just reverse the drill and back the bit out then try again easily. Once you get completely through the bowl, the edges will be extremely sharp. Smooth them out with a round file if you have one or some sand paper, but be careful.
angelikaengel (author)  diyoutdoorsman5 years ago
Wow, super instructions. The only thing I am not clear on is whether I am drilling from the outside bottom of the bowl with the bowl inverted on the table or if I am drilling into the inside bottom of the bowl, with the bowl bottom directly on the table. I trust this question makes sense. Thank you!
I would invert the bowl so it would be easier to clamp to the table. It would also be helpful to have a block of wood under the bowl to keep the bottom of the bowl from flexing while you drill. A chunk of 2x4 would probably do depending on how deep the bowl is.
onrust5 years ago
A hole punch like this. I usually get them used at pawn shops.
angelikaengel (author)  onrust5 years ago
This is a whole new approach. I have never seen one of these. I had imagined there should be something similar out there. How does one use this? Happy just to have you provide a link that I can read. Thanks.
Its called a knockout punch and these work great, but you still have to drill a pilot hole. You didn't say what size your valve was, but if it is much over an inch, this would be a good way to go. Otherwise, since you have to drill a hole anyway you may as well just use the right sized drill bit.
sam D5 years ago
If you drill with a normal drill, put some sticky tape down first. It will stop the drill sliding around until it starts to dig in.
angelikaengel (author)  sam D5 years ago
Thank you for the tip. Is 'scotch tape' OK?
seandogue5 years ago
If you don't have access to either a venier or dial caliper to measure the diameter, you can ask an attendant at the hardware store to tell you the final drill diameter required.

To set the bowl up for drilling:

1) Locate the hole and mark it using a sharpie or other indelible marker.

2) Place the bowl on a block of wood and use a hammer and marking punch to place a small dent where the hole will go. This mark will assist you in drilling the pilot hole

3) Using a 1/16-1/8" diameter drill bit, drill the pilot hole

4) Slowly increase the size of the drill bit until you reach your final drill size.

5) By hand, using a drill bit that's slightly larger than the final hole size, gently twist to remove any imperfections from the edge of the hole. install drain-cock.