I made the world's tiniest table saw by by taking a brushless dc motor, a
small spindle and belt, and a 545 diamond mototool cutoff wheel and mounting
them to the bottom of a piece of aluminum.

Makes smooth, clean exceptionally noisy cuts but that dust is deadly.  I use
a full painter's mask and only cut outside.

DougM


On Mon, Feb 15, 2010 at 10:03 AM, Brooke Clarke <brooke@pacific.net> wrote:

> Hi Don:
>
> I just looked at a bunch of boards under a microscope and can see some
> type of sub surface disturbance (fracture?).  On those boards the cut
> lines are actually traces that are 0.006" wide.  I cut these just by
> eyeball alignment and in the vast majority of cases the cut line is to
> either side of the trace.  (I'd like to do be able to cut exactly on the
> cut line, but so far have not found a good way to position the boards.)
> Those cut line traces, are in tact except where the cut line crosses the
> trace.  So if by fracture you mean a crack on the top surface that would
> cause an open circuit trace then I'd say no.
>
> When using tin snips where the distance between the hinge and active cut
> is a few inches the fracture effect is much stronger.  Just past the cut
> the two sides get rotated relative to one another putting a lot of
> strain on the material at the cut point.  When using the 12" shear
> there's so much leverage that cuts can be made at the very front of the
> blade which is over a foot from the hinge so the angle between the two
> cutting edges is very small, hence much less strain on the PCB.
> http://www.prc68.com/I/12InShear.shtml
>
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
>
>
>
>
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