Really should not be using HSS blades. Here is a link to information regarding FR4 PCB.
http://drum.lib.umd.edu/bitstream/1903/8362/1/umi-umd-5671.pdfchapt 2. has information on the composition of the FR4 core. And it says "The woven glass (generally E-grade) fiber cloth acts as reinforcement for the laminate, primarily providing mechanical strength and electrical properties."
E-glass. It is basically the same kind of glass as in your windows, glass bottles... HSS blade will dull very quickly and be ruined. Have you tried to cut glass with HSS blade? I use a diamond scribe to score a glass. We also have a diamond coated abrasives to trim stained glass. We always use water. I have near phobia level fear of glass powder. Silicosis is not good at any age.
And those working with fiberglass fabric S-glass, E-glass, kevlar and carbon, they buy scissors by the box load and throw them away as the blade gets dull. Pair of fabric scissors are lot cheaper than a tin snips. And tin snips last just as long as regular fabric scissors and not much more. If you want exercise in frustration, cut a glass fabric at an oblique angle to the direction of the weave. Hint, use adhesive tape near the cut.
And yes for this reason, preference is for carbide tipped blades and drill bits.
--- In Homebrew_PCBs@yahoogroups.com, jeremy youngs <jcyoungs76@...> wrote:
>
> because the glass reinforcement in the board is very hard
>
> On Sat, Dec 22, 2012 at 12:22 AM, Corey Minion <csminion@...>wrote:
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> > ∗∗
> >
> >
> > Why would fiberglass dull blades any faster than yellow or red brass or
> > any other metal for that matter?
> >
> >
> --
> jeremy youngs
>
>
> [Non-text portions of this message have been removed]
>