Homebrew PCBs

On Mon, 22 Jan 2007 21:05:45 +0100, Roland Harriston <rolohar@...>  
wrote:

> Ha!
> Stefan Trethhan you are so correct!
> I just went to the drawer in my worktable to fetch my carbide scribe and
> it is not there anymore!
> And I just used it a few weeks ago. Funny how those kinds of things can
> appear and disappear
> at will.
> I have a bunch of snapped-off carbide drill bits, and I will try to
> mount one of them in a little
> pin vise (used for miniature drill bits) and see if it works as nice as
> my missing carbide
> scribe.
> A diamond scribe would probably be better, but they cost a bit more than
> the few bucks
> I paid for the carbide scribe.
> Roland F. Harriston


Yes, stuff just hides all the time...

I'm not sure a diamond scribe would actually be better, since i don't  
think it has a narrow long tip.

The scribe we made in shool was to learn using a lathe, basically just  
round stock nicely turned with a taper at the front and knurled, then sand  
blasted. A hole in the tip to mount the drill (with loctite).
They used to cut a thread on the drill and into the scribe, and screw it  
in, but then they stopped making PCB drills with only the thin part  
hardened and you could no longer cut threads on the solid carbide drills.

I do not actually know how the broken drill was sharpened, i was ill that  
day and someone else did it for me ;-). But i always assumed they simply  
ground them by hand on a plain bench grinder.

Would be a 5 minute job to make a holder with a grub screw, especially if  
looks are not so important.
I keep all my broken drills, just for that purpose, although it might be a  
bit silly to keep them all since i didn't actually use one so far.

ST