Hmmm. It all depends where they're made and by whom.
I'm guessing these "CNC" drill bits are short with a larger shank. If they're carbide, they are very brittle compared to HSS bits. But not all carbide bits are as good as some others, it's all about quality, and that applies with both types of material.
When using tiny drill bits in machines, we're talking about very high spindle speeds. But when using them by hand in a pin vice, we don't have that luxury, also we can't have the same feed rate as would be possible with the bit spinning very fast.
Therefore we are talking about a very slow process when doing it by hand, constantly removing the bit to clear the waste, it's something that can't be rushed. Drill bits snap for three main reasons; Manufactured incorrectly.
Not being kept straight, mostly by uneven pressure.
Not removed frequently enough to clear the waste.
With the smaller drill bits, another two factors could be taken into account. The way they're sharpened, causing too aggressive a cut, which can cause the bit to snag during the cutting. Or the material being drilled is either causing a bigger chip by its nature, or causing a tighter hole than the size being drilled, and hence jamming the bit.
Funny enough, I've volunteered doing a small drilling job for someone, because, hey, how hard can it be for a know it all with only hand tools. . . .
I ended up ordering some better quality drill bits as the material was very brittle.
Then I decided on a different tactic, and ended up ordering some brass micro tube to completely fabricate an inner barrel, then realised the inner barrel is tapered, and now I'm trying to work out how to taper the barrel without splitting the tube.
All good fun
