Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

@markus:
i fear helis are to expensive for me (now)
would love to have one (some day)


the rails:
the fr4 is really very abrasive, you can use the edge of a board as a fine
file.

i think printer rails are not sturdy enough.
i store the rails from two similar printers (actually only the size is
different, one was a4 and one a3).
thought i would use it some day..

the rails are 12mm steel (not hardened, easy to cut a thread on).
the carriages are cast aluminium with bronze (or similar) sliding bearing.
the bearings have a bit of play.
i fear those rails won't hold up in fr4 drilling dust (maybe a hoover can
remove it before it hits the bearings).
one is already a bit scratched (from long years use) and also has much more
play.
i gave up on using these already (in the moment they are a cd stand - the
12mm hole fits exactly the rods).

also 12mm would be to thin (without additional support) to make ways for a,
lets say a4 size, mill...

most industrial rails have a wiper for the ways mount on the carriage.
this helps a bit to prevent dirt coming into it.

i would suggest putting the rails high enough to keep most material below
them.

if there is no other way it may be possible to protect all ways with a
cover, i saw this on a grinding machine for
hard tools and it seems to work. but i think this will show up during
useage if needed.

On the other hand the ball bearing method is better for abrasive dust.
imagine a piece of glass fiber coming into a bronze sleeve.. it may stay
there and be dragged along the whole
way. but if you have a rolling ball bearing on a flat surface the glass
fiber piece might just be run over.
and the bearings itself are so dirt cheap you can replace them often (they
are sealed and made for road dust/sand and
will never need replacement).

stefan