Homebrew PCBs

In a message dated 1/12/2003 12:39:07 PM Central Standard Time, 
dave_mucha@... writes:


> It seems like the box of 50 burrs from Harbor Freight are the best bang for 
> the buck, IF they last.
> 

Dave:  You didn't mention if these are solid-carbide, diamond-"plated", or 
what.  Carbide holds up well against such as FR-4 ("glass-epoxy"),  Diamond 
would "forever", if the diamond were the ONLY material touching the 
glass-fibers, but that "diamond plated" stuff is just that:  They 
nickel-plate diamond-grit onto a HSS spindle, so as soon as the nickel 
outer-"skin" is worn off (within first two seconds of use!), there is little 
"holding" the diamond bits on the steel.  AND, there is plenty of steel 
(nickel-plated or not!) exposed to the glass-fibers, between the rather OPEN 
grit-area, at the start!  

I found out LONG ago that even the "new wholesale" price of solid-carbide 
drill-bits (often more than $2.00 per bit!) is cheaper "per hole successfully 
drilled" than ANY HSS drill-bits, even if you can resharpen them yourself 
(every twenty holes?), and have a "chuck" capable of gripping HSS bits, which 
are NOT made with "One Size Fits All" 1/8" dia. shanks as are carbide bits.  

A carefully-zealous "browsing shopper" can find BOXES of useful-sizes of 
solid-carbide bits offered in the various mail-order catalogs such as JDR 
Microdevices and JAMECo, etc.  I don't know that their current pricing is 
like, but I have bought several boxes of 50 "reconditioned" bits of size #57 
or #65, etc., for less than $1.00 per bit!  NEVER throw away the 1/8" shank 
when the "drill-part" breaks off, as that is VERY useful "tool-making stuff"! 
 All you need is a little diamond-wheel on a little grinder-motor, some 
imagination, and minimal skill!

I do not "machine-etch" PCB's (easier to chemically-etch!!!), but I note 
there are many "of us" who do, and I wonder why no one has offered that these 
busted, "useless" (NOT!) solid-carbide drill-shanks would be ideal for the 
tooling on a machine-etching job!  Ya just have to grind an "engraver's tip" 
on the pointed-end of the shank (where the drill-part left for a galaxy far, 
far away)!   True, one must have a nice small lathe (Unimat, Sherline, Taig, 
etc.), if not a "bit holding fixture" and a diamond-cup-wheel grinder rig, 
and some wisdom and skill.   Some may-well know a "machinist-friend" who 
grinds his own tooling, who will do these as a favor.  Might be a "project" 
for some ambitious soul!  Others might find some grinding-shop willing to DO 
this "for us all" at a reasonable price, mail-order---we just supply the 
shanks/blanks.  Can someone with more wisdom on this point comment???

Jan Rowland, old troll








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