As raven says, you should buy the drill bits that you need for tapping metric holes.Dog Tyred wrote:Thanks Tapio, really useful stuff![]()
Assuming of coarse you have a 6.8mm, 8.5mm or 10.2mm drill bit !!
DT
But what if it's late saturday night and you have a strong craving to do a M8 tapped hole?
Can't find your 6.8 mm drill bit?
Your local waterhole for drill bits' manager is reluctant to open up his shop for you to buy a drill bit?
Bring out your drill bit set. They typically come in increments of 0.5 mm.
You take the 6.5mm drill bit and grind one of the cutting edges slightly longer than the other.
This makes the drill bit wobble thus making the hole slightly larger.
It's tricky to know just how much longer the egde needs to be, so you should always try it on a scrap piece first.
Also, you cannot do this by starting out with a small drill bit, and enlarge the hole in steps with bigger and bigger drill bits. The final drill bit won't wobble then.