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Before starting to drill a hole, you will need to centre punch the surface of the metal to provide a start for the drill bit, preventing it from slipping or skating across the metal pipe or plate, and ensuring accuracy. Mark the metal where you want to drill, and then line up the point of your centring tool – hitting it firmly with a hammer to produce a small round indentation. If you are drilling through thin metal you may need to place something behind it to prevent creating too large a dent, or if drilling into a metal pipe, tap lightly and start your pilot hole with the smallest drill size you have available.
To start your hole, it is best to start with a pilot hole – a narrower bore in the metal than what is required, and then change up to a larger size drill bit. If you have a power drill that is not particularly powerful or are drilling through metal that requires a slower drilling speed, you may also want to make an intermediate sized hole – for example 4mm > 8mm > 12mm.
It is essential to keep the drill bit as sharp as possible or else there is the chance that it will overheat and damage the bit beyond repair. For the same reason lubrication may be required – especially if drilling a hole deeper than the width of the bit (and always on stainless steel). Speed is another factor to consider. If you drill too fast, you will over heat the drill and the metal edging of your hole. If you drill too slowly, you will not get a clean edge on your hole and although sharp edges and burrs can be filed down once the job is complete, they are a safety hazard whilst you continue to drill.
Manufacturers of variable speed power drills will usually include a guide to drill speeds with the tool´s instruction book and, although it is always recommended to follow the manufacturer´s instructions, should you not have access to one, please click here to access Mr Skill´s Guide to Drill Speeds. If you do not have a variable speed drill, or one which operates faster than the speed you wish to drill at, intermittently release the trigger and give the RPM of the drill a chance to slow down.
Safety Advice
When drilling metal you should always wear goggles and keep a good grip on your drill. Do not use a drill if it has a frayed electrical cable or when working near water. Wear gloves wherever possible and remove metals shavings with a soft brush and then wipe down the area with a disposable cloth.
If you do not have adequate tools for the job or have allowed your drill bits to become blunt or damaged, do not attempt drilling through metal. Instead get quotes from builders in London through our “Post-a-Job” facility at the top of each page and stay safe!