How do I drill drainage holes into a large galvanized tub?

Most drill bits will be fine. Generally the bits we homeowners have are metal/wood rated- just go slow. Galvanized metal isn’t to hard to drill through but the edges could be sharp

I agree, most bits will work fine as most bits that people have are metal/wood rated. You can purchase specific metal bits too.

Pam: Yes a standard drill bit will work. ...and yes, it will be sharp around the hole. If you make an "X" with masking tape (for each hole), this will help -- and help the drill not to slip as easily.

Make sure to put some rock or brick pieces in the bottom -- before adding soil -- for further drainage help

If the metal tub is relatively thin I would expect any drill bit would be fine. Sometimes placing a coffee filter in the bottom and maybe some Styrofoam peanuts as helpful so the soil does not wash out the drainage holes.

You should be fine with a standard drill bit, but it may not be necessary. You could fill the bottom with old plastic containers (juice, milk, etc.) for drainage and those things will not add weight to the tub. I used them in a trash can I turned into planter:

https://theapplestreetcottage.blogspot.com/2015/06/trash-can-to-planter.html

Before you begin to drill, put on a pair of safety glasses, there may be metal filings that could fly off in any direction. A galvanized tub is fairly thin metal, so just about any drill bit will penetrate if.

Take a center punch and make a mark with the punch by a tap with a hammer, this will make a dimple where to start the hole and keep the drill bit from wandering.

You may want to spray the new hole with a Cold Galvanizing spray-available at diy stores, it is RustOleum Professional Galvanizing Compound Spray, a produce made mostly of zinc. This is to prevent corrosion of the galvanized metal.

I used empty water bottles in the bottom of my tub for drainage, much lighter than stones.

No. A standard drill bit should cut through nicely. They do make drill bits for metal but galvanized is not all that tough to drill.

You can use any drill bit that will work for metal. Make sure to wear protective eyewear and clothing. There are tiny metal shards that will fly everywhere.

Once you drill them, take a piece of rough sand paper and smooth the edges or you might cut yourself later down the road.

Others have given good advice on drilling. I'll add that you can also put a layer of gravel or rocks in the bottom to help with drainage if you end up not drilling it.

A high speed steel drill bit for metal is all you need. Different bits are made for wood, plastic, ceramics, and metal. The tip angle and flute twist are different.

I have galvanized tubs and I use them as planters, but I might use them for other things in the future so I didn't want to drill holes in them. Instead, I line the bottom with about 2 inches of pea gravel and then I add the dirt on top. I've never had problems with drainage. The plants thrive and if I want to use the tub as a fountain or pond in the future I still can.

Otherwise, I would use a metal drill bit and watch for sharp edges.

Thanks all for your answers! I had already put plastic bottles in the bottom but since I live in NC I am very concerned about standing water and mosquitoes. I’ve been throwing those mosquito dunks in but haven’t been able to get the water to evaporate so now I’m just going to drill a little drain hole so I won’t need to worry about standing water and mosquitos

I used a regular drill bit no problem!

You will need to drill more than one hole. Probably several 1/4" ones. This is interesting

https://www.quora.com/What-is-a-good-plant-drainage-material-for-a-potted-plant

here is a good video https://www.pinterest.com/pin/3096293472715742/