I want to drill a hole (about 12mm diameter) through the floor of a shipping container. From the inside of the container, the wooden (probably plywood) floor is visible, and from the outside there is the steel hull. I have no idea what is in between those two layers.

How do I get a hole through the whole floor?

2 Answers 2


Unless this is a powered shipping container, e.g. one with a builtin refrigerator or other such features, there's probably nothing interesting between the plywood floor and the steel skin. So just get a drill bit suitable for steel and have at it.

  • So, use the steel bit for both wood and metal?
    – Jasper
    Commented Mar 13, 2022 at 11:03
  • 2
    @Jasper Sure. It won't give a perfect finish in the wood, unless you clamp another piece of wood on top, but it'll work just fine. Given that it's a shipping container, the finish is probably not #1.
    – vidarlo
    Commented Mar 13, 2022 at 14:11
  • @Jasper I have a cheap set of twist bits that I commonly use in both wood, steel, aluminum, and plastic. It works perfectly acceptably in all materials even though they're not ideal for most of them and the use in steel has probably dulled them enough that they don't cut all that well in wood any more. I use my nicer bits for actual woodworking projects where I care about the quality of the cut.
    – FreeMan
    Commented Mar 14, 2022 at 13:58
  • Important tip: Once you're through the wood and drilling into the steel, stop and apply a few drops of a light oil to the bit to help keep it cool and cutting better through the steel. You'll want to pull the bit out of the hole and apply the drop or two of oil every 10 seconds or so, just to ensure you don't overheat the bit. The wood will help insulate the bit and keep even more heat in, so it's important to keep the bit cooled. If you don't, the heat will cause the bit to dull even faster and will frustrate you, though you'll make it through eventually.
    – FreeMan
    Commented Mar 14, 2022 at 14:00

Drill through the wooden flooring first, shine a light into the hole, when you'll be able to see or feel what's directly below. If it's the steel bottom (an magnet would prove) then using a drill bit for steel, carry on through. If there's something else in the way 9doubtful), you can always fill the hole in in the wood, if needed.

An auger may do a better job in the wood, but a tungsten carbide, etc., bit will do both.

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