PC BOARD DRILL BITS

[Tom Hammond-3]

Just a note for builders, especially those who make their own PC boards.

While you CAN use high-speed steel drill bits to drill your
glass-epoxy PC boards, you'll find that they (the bits) will dull
very quickly (sometimes within the first dozen holes) due to heating
(especially when turned at high rotational speeds) and the dulling
effects of the fiberglass in the PC board substrate.

For drilling holes in PC boards, drill bits made of Tungsten Carbide
will last MUCH LONGER (typically several THOUSAND holes), even when
turned at very high speeds.

The problem with carbide bits though is that they are EXTREMELY
BRITTLE and will break if you even look at them askance, or if
they're subjected to lateral stress. Run them straight up 'n down and
they'll last for a LONG time, but apply even a small amount of
lateral stress and you'll be replacing the bit in a heartbeat. JUST A
WORD TO THE WISE SHOULD BE SUFFICIENT.

For the past 20+ years, I've been making my own PC boards... in the
kitchen... with the kind forbearance of my dear XYL, Jeri (K0RPH).
And I've been using an old Dremel MotoTool, secured in a drill stand
designed to hold the device, for virtually all drilling tasks. The
drill stand allows me to run the drill motor (and bit) straight up
and down, with virtually no lateral stress on the bit (unless I try
to move the PC board before the bit's fully exited the last-drilled
hole (bad things happen then!).

I've had problems finding reasonably-priced suitable tungsten-carbide
bits however. Most new bits run $4-$5 (US) each and I shudder to
think of breaking one each time I chuck it up into the drill motor.

I found a semi-local source of used bits (but still good for a few
thousand holes), but I think he's no longer available, so I've had to
search for another source. Fortunately a friend, Willie, KH6NO/7, has
found a source of resharpened tungsten-carbide bits in Drill Bit City...

http://www.store.yahoo.com/drillcity/restool.html

While the prices ($0.90/bit) are not those I was paying a year or two
ago, they're still a LOT better than 4X to 5X that price, for bit
which will break just as fast, and which won't drill any more holes
than a resharpened bit.

Just thought I'd bring this to the attention of anyone who might be
searching for a more reasonable price for their PC board drill bits.

A sharp tungsten-carbide bit, chucked up in a high-speed drill motor
will go thru PC board like a hot knife thru butter.

Enjoy.

73,

Tom Hammond    N0SS

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[stephen Farthing]

Tom,
    You are dead right about the fragility of the bits. I was lucky
enough to pick up a couple of boxes of bits at Dayton a few years back,
50 bits per box, $5 per box, the guy had loads, they were new too, guess
I was lucky.

Regards,

Steve
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[Alexandra Carter]

Tungsten carbide bits live a LOT longer if they're used an a drill
press, they just can't stand ANY side forces. 73 de Alex NS6Y

On Apr 23, 2006, at 7:11 AM, Tom Hammond wrote:

> Just a note for builders, especially those who make their own PC
> boards.
>
> While you CAN use high-speed steel drill bits to drill your
> glass-epoxy PC boards, you'll find that they (the bits) will dull very
> quickly (sometimes within the first dozen holes) due to heating
> (especially when turned at high rotational speeds) and the dulling
> effects of the fiberglass in the PC board substrate.
>
> For drilling holes in PC boards, drill bits made of Tungsten Carbide
> will last MUCH LONGER (typically several THOUSAND holes), even when
> turned at very high speeds.
>
> The problem with carbide bits though is that they are EXTREMELY
> BRITTLE and will break if you even look at them askance, or if they're
> subjected to lateral stress. Run them straight up 'n down and they'll
> last for a LONG time, but apply even a small amount of lateral stress
> and you'll be replacing the bit in a heartbeat. JUST A WORD TO THE
> WISE SHOULD BE SUFFICIENT.
>
> For the past 20+ years, I've been making my own PC boards... in the
> kitchen... with the kind forbearance of my dear XYL, Jeri (K0RPH). And
> I've been using an old Dremel MotoTool, secured in a drill stand
> designed to hold the device, for virtually all drilling tasks. The
> drill stand allows me to run the drill motor (and bit) straight up and
> down, with virtually no lateral stress on the bit (unless I try to
> move the PC board before the bit's fully exited the last-drilled hole
> (bad things happen then!).
>
> I've had problems finding reasonably-priced suitable tungsten-carbide
> bits however. Most new bits run $4-$5 (US) each and I shudder to think
> of breaking one each time I chuck it up into the drill motor.
>
> I found a semi-local source of used bits (but still good for a few
> thousand holes), but I think he's no longer available, so I've had to
> search for another source. Fortunately a friend, Willie, KH6NO/7, has
> found a source of resharpened tungsten-carbide bits in Drill Bit
> City...
>
> http://www.store.yahoo.com/drillcity/restool.html
>
> While the prices ($0.90/bit) are not those I was paying a year or two
> ago, they're still a LOT better than 4X to 5X that price, for bit
> which will break just as fast, and which won't drill any more holes
> than a resharpened bit.
>
> Just thought I'd bring this to the attention of anyone who might be
> searching for a more reasonable price for their PC board drill bits.
>
> A sharp tungsten-carbide bit, chucked up in a high-speed drill motor
> will go thru PC board like a hot knife thru butter.
>
> Enjoy.
>
> 73,
>
> Tom Hammond    N0SS
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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> Elecraft web page: http://www.elecraft.com
>

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