What I used for many years is a little surplus 27V DC (brush
type)instrument motor. I had a machinest at the local hobby store make
me a coupler the connect the motor shaft to a pin chuck from a old dead
flexable shaft.
The first KEY is that the unit is small enough to be held in the and
between the thumb and fingers, this makes for easy drilling. I power it
with about 40V from through a foot switch. The second KEY is to set the
foot switch up to short the motor winding out when you let you foot off
the swtich. The short stops the motor is less than a second which is
important so the bit doesn't wander when moving to the next hole. The
third KEY is to make sure there are .005 to .025" dia no Cu holes in all
the pads on the board you want to drill. This acts like a center punch.
Put the bit in the void hit the foot swithch, dirlls quite fast. I do
have to let the motor cool a little after bout a 100 holes or so.
You can only use HHS wire drills, carbide bits are way too brittle and
will snap with the first hole. Keep a small pocket stone around to
resharpen the drill bits ever so often. I am going to make a tiny disk
sander from another small motor to sharpen bits.
Yesterday I had a nice $15 find at my local surplus store. Its an air
bearing brushless 3 phase dc spindle motor and should make a nice PCB
drill spindle for my CNC Bridgeport. From what I can tell the motor was
designed for Hard Disk platter testing and production equipment and
shoud spin up to 30,000 RPM. Don't know the power but I shouldn't need
much to punch through .063 FR4 at 30K with carbide bits.
Anyone have any suggesitons or ideas on what I should do for a chuck
design. Also be interested on suggestions for a burshless motor driver
IC as I will have to build a 3 phas power supply for the motor.
Here are some pictures of my hand drill and new spindle motor:
Pictuer Link <
http://picasaweb.google.com/cschaffter/PCB_Stuff#>
Craig
[Non-text portions of this message have been removed]