Homebrew PCBs

In a message dated 26-May-02 06:09:15 Central Daylight Time, 
john@... writes:


> The problem with Mechanical Etching is the epoxy in the board. 

Correction, if I dare:  The "epoxy" is merely easy-to-cut "plastic stuff"!  
It is the GLASS FIBER impregnated in the "epoxy" which eats up cutting-edges! 
 

I suspect the main reason alternatives of pointed "engraving" bits is 
considered here is that such a TINY portion of tool is "in the work" at any 
instant, it therefore has to TURN at such a tremendous speed to have any 
suitable "surface-speed" to work, at all, whereas the CIRCUMFERENCE of even a 
1/8" dia. bit would have much more surface-speed, even at slower RPM.  That's 
why a modern dental hand-piece turns those tiny "burrs" (mill-bits!) at 
100,000-300,000 RPM and more!).  Tip:  Dentists typically throw-out used 
burrs, even if only "package opened, but not actually used".  Next time you 
have 3 grams of amalgam put in  your face, ask the dentist if you can HAVE 
"your" used burrs (you HAVE paid for them, after all!).  These will 
(usually?) have 0.0625" dia. shanks, yes, even those built-in and USED-in the 
rest of the world, I think!  So, you will have to use the correct collet, 
etc.  But those can probably do "mechanical PCB etching" very well, if turned 
at least 30,000 rpm or more.  Think AIR-MOTORS!!!  Whew, even if the "main 
spindle-bearing" were dual-race angular contact ball-bearing, a "Dremel tool" 
just isn't the kind of "quill motor" for a PCB drill!


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