Thank you for the information, Tom.
Real intelligence from someone in the business is invaluable. I haven't purchased resharpened bits in a very long time, but when I used to do it, microscopic examination of the points convinced me they were actually re-pointed (I did return a batch of unsharpened bits once; kind of funny at the time). Things have probably changed since then, so it's good to get that pointer (pun intended :).
Donald.
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----- Original Message -----
> From: "twb8899" <twb8899@...>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Sent: Thursday, February 24, 2011 12:45:09 PM
> Subject: [Homebrew_PCBs] Re: Carbide PCB drill ?
>
> --- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@...>
> wrote:
> >
> > Does any one know when the commercial guys have their carbide PCB
> > drills sharpened do they just dress the tips or do they grind the
> > flutes as well?
> >
> > Just wondering if resharpened drills will drill a smaller hole after
> > sharpening or are they just a little shorter.
> >
> > Was thinking of getting some resharpened drills for the shop.
> >
> > Craig
> >
>
> I was in the printed circuit business for many years and drilled
> several million holes per month. We used new bits for multilayer
> boards and replaced them after 2500 or so holes depending on the
> customer and project. After multilayer drilling the bits were sent out
> for re-pointing then used again for two layer boards up to
> approximately 3500 holes and re-pointed again. After the second
> re-point the bits were used only on single layer boards until they
> were worn out or broken.
>
> I paid around $1.75 USD per bit for middle of the range bits such as
> .028" to .125" etc. The smaller and larger sizes cost more due to
> complexity and/or cost of carbide. The cost to re-point any size bit
> was $0.25 USD each and this included new depth rings. All of this took
> place over ten years ago so I don't think those prices would be good
> today. Even though it was inexpensive to re-point I eventually bought
> a sharpening machine that had diamond wheels, drill bushings and a
> microscope. From then on I bought new bits and maintained them in
> house.
>
> We actually broke very few bits but I kept all the carbide shanks and
> now grind them into engraving bits and other small cutters for the CNC
> machines I use today. The only way to know how many times a bit has
> been re-pointed is to measure the flute length and compare it to the
> original specifications. Many sellers of "resharpened" drill bits are
> actually selling used bits which are fine for hobby projects even
> though they aren't very sharp. I hope this answers some of the
> questions concerning pwb drill bits.
>
> Tom
>