Using the ever so simple centre punch…
If you’ve tried drilling holes in metal before you’ll remember the drill bit ‘walking’ all over the metals surface instead of starting the hole exactly where you wanted it. This is because metal is hard (I know this is free advice but Duh! Of course metal is hard, when are you going to tell me something I don’t know?)
OK, so you know that metal’s hard, but did you know that if you make the tiniest of dimples in the metals surface, the drill bit will dive after that hole like a man who’s dropped his ice cream on the beach? Yup, because the metal’s hard and the drill bits even harder (another Duh!), nothing is going to happen unless you give it a head start.
Using a centre punch ensures accurate holes when drilling metal.
Using a centre punch couldn’t be easier. One hit is all it takes. In fact, try to resist giving it several hits (if one hit is good, then three is better right?). No, not in this case. Hitting the centre punch several times is more likely to move the hole, whereas one, hard, sharp hit, right on the button will do the job. You’re only giving the drill bit something to grab a hold off, not trying to make the hole with the centre punch!
Even if you press really hard on the drill bit, it’s always going to twist away from your pencil mark as the bit tries to get started. The only exception to this rule is if you’re using a fixed drill pillar and even then, centre punching your marks will still improve your accuracy and prevent smaller diameter drill bits from snapping.
The image above shows some back plates I modified today to fit the customers mounting points in the wall and although the actual placement of these holes wasn’t super critical, when the first one wandered off my pencil marks I thought Ooh, this would make a good tip and here we are. As you can see from the pic, the holes on the right hand plate are slightly off the pencil lines. On the left hand plate, the tiny dimples left by the centre punch were more than enough to help the drill bit stay true to the pencil marks, as you can see on the middle pic.
Safety Notes When Drilling Metal
- Always securely clamp the workpiece because drill bits grab as they exit and will turn unsecured workpieces into sharp propeller blades, good for chopping bits out of you…
- Drill large holes using a series of increasingly larger drill bit sizes.
- For very thin sheet metal cut a hole into a piece of wood (larger than the one you want in the sheet) and clamp this wood over your marks in the metal and onto another piece of wood to drill into (I’ll do a separate post on this later…)
- Gloves and goggles are as always a good idea when working with sharp metal.
Hope that helps you drill more accurate holes in metal!
Stay well
Ian
