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Home-Brew CNC PCB Drill

2004-03-24 by Jan Rowland

I had been thinking I had ALREADY added this [subject] photo to the 
group, but, well, guess it's Alzheimer's!  This quill has a 400 Hz. 
12,000 RPM AC motor in it.  Some machining to replace 1/4" shaft 
on "bottom end" of motor with 1/8" collet/nut!  And ABEC-7 bearings.  
That "quill motor" is powered by simple "push-pull" 400 Hz 
multivibrator and 95 VA transformer purpose-wound for the 
application.   I had used the old PET you see for years, but the last 
of several I had on hand finally gave-in to alpha-particles, so I'm 
slowly getting around to converting the 8-bit interface (yep, just a 
9-wire cable to puter!) to work through a PC parallel printer-port.  

The little blue motor atop the quill is a Slo-Syn 72 RPM SS-25 that 
rolls a tiny cam-follower roller around a 1/4" pitch helix.  So the 
quill-travel is abotu 0.24".  The quill can "do a hole" or "go down 
and stay until told to return to "home".  This latter way, the 
machine can engrave.  

The screws are 1/2" lead (1/8" pitch/4-start) stub-ACME.  Thomson 
linear ball-bearings/ways.  Baltic birch base.  Formica-covered top.  

Can do about 3000 holes per hour, drill-rate.  (one bit-size!  Takes 
time to change bits!)                  Jan Rowland

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