2mm diameter drill bit bends?

[Phil Pascoe]

The jaws don't necessarily centre properly when gripping the helix. That's what I've found, anyway.

 

[Fergie 307]

why is it more accurate to cut down the tip than the shaft? I would have assumed that a factory machined tip would be be more accurate than a home sharpened tip, so better to reduce the shaft where accuracy is not important.

I can only think that reducing the shaft would leave the chuck gripping onto the grooves / auger rather than a smooth shaft which could introduce error, am I on the right grounds??

I wonder whether a collar (with an opening / gap down one side to allow for tightening) down the length of the bit would give the extra bit of support needed

It is simply because the fluted part is necessarily weaker that the solid part, and so more likely to bend. A stub drill will typically only have maybe 2 times it's diameter of flutes, the rest being smooth.

 

[worn thumbs]

So if it has a run out, you drill a 2mm hole it ends up 2.2mm ?

Not very likely.That would require a rigid drill bit rotating eccentrically and the tip of a 2mm drill bit isn't connected immovably to the shank.What usually happens is that the rotation continues and the flexing of the bit with each revolution leads to a breakage.

 

[Rhossydd]

One thing no one else seems to have mentioned is the quality of the drill bit. Lots of the hss drill bits sold cheaply or in sets are rubbish, especially the smaller sizes.
I had to drill hundreds of small 1.2>2.2mm holes in brass sheet during lockdown and getting high quality German drill bits transformed the task.
Go on eBay and search for Heller 2mm HSS drills and buy a box, not expensive, but very good IMHE.

 

[Phil Pascoe]

An acquaintance who has worked for a builder's merchant for many years told me he was always amazed at the number of people who spent a small fortune on top of the range power tools then complained of poor performance after using the cheapest bits and blades they could lay their hands on. A first class bit in a second class tool is usually better than a second class bit in a first class tool.