"Larry Jaques" wrote in message
...
On Fri, 2 Dec 2016 07:17:31 -0500, "Jim Wilkins"
wrote:

"Michael A. Terrell" wrote in message
news
Jim Wilkins wrote:
...
The frames broke on these, near the die. I wore out a lot of
punches, before the frame died of metal fatigue. I used to do a
lot
of prototyping, with hand tools. Trimming fiberglass circuit
boards
to fit into a case was the worst for wearing out the tool.

I've worked at a few places, notably Mitre, that had good facilities
for both electronic and mechanical prototyping but that wasn't the
case at smaller startups developing some new idea on a tight budget.
I've nibbled, filed and sanded a lot of circuit boards to size
including the mechanical-fit models for the Segway balance sensor
assembly. At one place when the Dremel died I cobbled up a pump
drill
to finish a circuit board. Unlike a bow drill it applied no side
force
to the fragile carbide bit.

http://cart.occpaleo.com/stonetippedpumpdrill.aspx

For that price they could at least have found a prettier smoothed
river stone for the weight.

Do those rely on the inertial force of the spinning stone to work?
Wind 'em up, push down, and they spin until wound the other way.
Rinse, repeat?

Yep, push down, let it rise, push down...., while steadying the top
end with the other hand. It's less awkward and tiring than a bow
drill. Since it spins both ways a blunt spear point with flats on the
edges works well for the drill bit, and is easy to resharpen. You
could drill your first counterweight with a bow drill that doesn't
need one.

http://www.lowtechmagazine.com/2010/...-machines.html

When I was little we moved into an 1830 house that had a chest of
those old "cordless" tools, which I used until I was old enough for
power tools. The tricky part was learning how to keep them sharp.

--jsw