The HSS bits will be fine for maybe 30 holes or so before
resharpening. Geometry doesn't matter nearly as much as when drilling
metals, so you can easily sharpen them.
If you don't plan on too many holes, it'll work, and they can be used
freehand without breaking.
Carbide drills make nicer holes for longer, but if that doesn't matter
HSS will be OK. You can buy 10 packs of just the size you need for
very little money.
What I noticed is drill hardness makes a big difference with FR4. If
you get a soft drill you may not be able to do even one hole. Recently
I tried to drill a 2.5mm hole and had to give up on the drill after
resharpening it 5 times. Obviously this drill (source unknown) was
much softer than proper HSS drills, it rounded out immediately upon
contact with the fiberglass. The next drill I tried completed the hole
with no apparent dulling.
Let's hope the harbour freight drills are decent hardness despite their origin.
ST
On Sat, Apr 18, 2009 at 10:43 AM, Alessio Sangalli <alesan@...> wrote:
> Thanks for the tips.
>
> I still think that would be a bit overkill to me... what do you think if
> I try these with my dremel by hand:
>
> http://www.harborfreight.com/cpi/ctaf/displayitem.taf?itemnumber=94606&Submit=Go
>
> even if they do not last many holes:
> - I am not drilling much
> - they have many bits in a package
> - it's cheap
>
> bye
> as
>