In this article I am going to address one of the most common questions asked by not so experienced handymen. The answer to this question can be only found on forums, so I am going to make your search easier and save you time on reading various different answers.
So, when drilling through a square tube the most important things are:
- the right drill press,
- the right drill bit, safety equipment,
- lubricated drill bit and,
- like in every relationship, it is necessary to take things slowly.
The primary thing would be to choose the right drill press, in this case a regular jobber drill would be grand for the job with a combination of drill bits for metal (titanium ones are recommended). It is also crucial that you use plenty of oil on the drill bit, and that you maintain a slower speed. If the drill bit overheats it becomes useless, an experienced person can drill all day with one drill bit whilst the enthusiast can go through three in one hole. This is also suitable for thicker materials. You also need to have your workspace secured and have a scrap piece of wood beneath if your drilling downward on a concrete floor; smaller bits (max diameter 10mm) require higher rpm and with larger ones (13mm) less rpm is needed.
The second best option would be a hole saw drill press set on its slowest setting and provided with good cutting fluid which will extend the life and speed the cut. One user gave a really useful tip which can save you from breaking the pilot drill when the saws teeth make contact with the steel you are drilling: Basically you can use a fender washer larger than the size of the hole saw and put it on the steel piece centered on the hole location you are about to drill, as you are applying pressure to drill the center drill hole, the pilot drill as it breaks through the steel, it is hard to hold back the pressure on the handle of the drill press and so the teeth of the saw will catch the steel piece and want to grab, thereby jamming the teeth into the steel and with this twisting action, sometimes breaking the pilot drill. This also is applicable when using a hand drill. By using a fender washer the teeth of the hole saw will make contact with the washer and spin the washer and not getting caught in the steel. Remove the washer and continue your cut and use your cutting fluid.
One of the things you can do is to drill the holes from each side of the tube rather than drilling through the tube. You will then have less friction by not having the hole saw bit down inside the tube through the first hole.
In the end I just have to mention that SAFETY comes first! Please protect yourself because consequences can be terrible.