Drills

Making round holes: Drilling with and without a template

A twist drill seems to be such a "normal" thing that it's hard to believe it's not much older than the first Harley-Davidson: the invention is attributed to a Mr. Martignoni from Ticino, the year is 1863. Such a twist drill is a marvellous thing: cutting edges set at an angle to the workpiece peel out chips, the helical flutes around the drill core remove the chips. Twist drills can be used to drill into the solid and they guide themselves in the drill hole, but they are not self-centring due to the small transverse cutting edge at the tip. They need a centering hole or at least a center point for the initial guidance so that they do not run off. Speaking of the drill bit tip: drill bits for metal are ground with a 118° tip angle as a standard, drill bits for plastics with 60°. This prevents the soft plastic material from tearing.

How do you drill the right way?

To ensure that the drill bit finds the correct position straight away and does not "wander" on the workpiece, you will center-punch of the future hole. An automatic center punch is more precise than one which is blown by a hammer. For round tubes such as handlebars you may want to use drill template which reliably prevents drill bit tip side tracking. The drill is positioned at a right angle. Sounds obvious, but it is not always the case, especially when working freehand. When drilling freehand, you can also follow the rule that the sharper the drill bit tip, the slower you drill and the less pressure you apply. Let the bit do the work, not your muscles. Otherwise, very sharp drill bits tend to get caught in the material and bend, or the drill bit bites off chips more than it cuts them. Both things will not allow perfectly round holes.