On Sun, 21 Jan 2007 08:38:07 +0100, David McNab <
rebirth@...>
wrote:
>
> I tried a jigsaw mounted upside down under a table - worked great for a
> few cuts, till the teeth wore out - I gave it up because I knew the cost
> of blades would quickly start to add up.
Also, you get glass fiber dust into the machine, which i'm sure makes a
great grinding paste combined with the grease.
There are two options - sawing and shearing.
Sawing gives a better edge, but is usually slower, more noisy, and dusty.
You can use a carbide blade in a small circular saw - that gives an
absolutely perfect smooth, square, straight edge. Looks even better than
professionally milled IMO. Proxxon makes such a blade and saw, for
example. Some also reported reasonable success with diamond blades in
tilecutters (wet), i have not tried that myself yet.
The second option, shearing, is quick, clean, quiet, and has virtually no
wear on the blades used. The only disadvantage is the edges are not as
clean, they are "broken". After a quick sanding they are nice enough
though. You can use bench mounted shears, for example bungard makes one
specially for PCBs but the sheetmetal ones work too. That type has a wide
blade that cuts the whole width at once. You can also use a bench mounted
lever shear, which is much cheaper, and has a blade about 15cm long, so
you may need to use several cuts for the larger boards, not a problem
since a lever shear is designed to let the sheetmetal run through. The cut
of the lever shear looks slightly worse than of the guillotine version to
me, i expect it comes from the slight twisting action of the cut. Another
option is a handheld sheetmetal shear "tin snips". Sturdy ones that are
designed to let the metal run through straight work quite well. I used
those for a while before the lever shear. Some people have also reported
success with larger paper cutters.
I can recommend the shearing, since there is no noticeable wear and no
dust. But the carbide blade in the circular saw made a fabulous cut, i
just wouldn't want the dust and noise all the time. For me the quality of
a lever-shear cut is easily sufficient, and i got one free, so that is
what i currently use.
ST