[Elecraft] PC BOARD DRILL BITS

[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
>
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