Tips for drilling metal
Tip 1: choose the right drill bit
For all drilling jobs goes: you can't do them effectively without the right drill bit. When it comes to drilling metal, the right drill bit is of course a metal drill bit. This drill bit has a very sharp point and a cylindrical shaft through which metal fragments escape. Want to drill a hole that's larger than 8 millimeters? Drill a 3-millimeter hole first, then drill again with a drill of your desired size. This prevents the drill from slipping off.
Tip 2: use a low RPM
The number 1 most commonly made mistake when drilling metal is using an RPM that's too high. When it comes to speed, the best thing is to take it easy. The larger the hole you want to drill and the harder the material, the lower you should set the drilling speed. If you're drilling stainless steel or inox with a 5-millimeter drill bit, don't turn the machine's RPM up beyond 600RPM. When drilling aluminum (softer than stainless steel), the same effect requires 1,500RPM. I could bore you with difficult ways to calculate the RPM, but just start nice and slow. If it's going a bit too smoothly, slowly increase the RPM.
Tip 3: prevent slipping
When drilling metal, the surface is often slippery. There's a good chance your drill bit might slip off on your first try, leaving a big scratch and making you angrily throw away your drilling machine. In order to prevent this, first use a sharp object to make a dimple. Placing the drill inside the dimple greatly reduces the chances of it slipping off. You can use a center punch or – nice and simple – a steel nail. Perhaps the best way to get that drill into the exact spot where you want it to drill is using a pillar drill. This does of course require the material you want to drill to fit underneath it.
Tip 4: cooling with cutting oil
Cooling is very important, especially when drilling hard metals like stainless steel, since one property of stainless steel is that it gets harder when heated. Drilling metal gets both the drill bit and the material extremely hot (don't touch either right after drilling!). If you're not cooling, the material will harden and drilling will get tougher and tougher. By using special cutting oil, you'll be cooling both material and drill. Drilling will be more effective and faster and – not entirely unimportant – your drill bits will last a lot longer, because their cutting edges will stay nice and sharp. Cutting oil can be found both in liquid form and in a spray can.
Drilling metal: it's either a job done right the first time, or a job you'll curse after many failed attempts. I hope you'll get to join those for whom it's the former, thanks in part to the tips listed above. You see, preparation is the trick. The right drill on a nice, low RPM, the right drill bit, and the right accessories will get you a long way.