On 2011-11-15, Searcher7 wrote:
[ ... ]
Thanks everyone.
To answer the questions, the grooves I have to make don't need to have
near perfect tolerances. I'm creating the grooves to place 3/16" wide
phosphor-Bronze strips in them for new contact blocks I'm making.
O.K.
If you were working with high frequency RF, Teflon makes a
wonderful insulator, but is probably overkill for the machines you are
working-with/modifying/making.
Making the grooves over-sized wouldn't be a problem because the 1/8"
distance between them is flexible. (In fact I may just go with 1/16"
between each groove).
You probably want the grooves slightly oversized to give the
fingers room to spring.
The grooves, are just to make sure the strips don't shift. The
finished nylon pieces will be 4-1/2" long, 3/4" wide, and 1/4" thick,
and the grooves will be on the opposite 1/4" sides. Each strip will
wrap around into it's own groove.(Which will probably be the toughest
part of this project).
O.K. Just two contacts per, then. Sort of like this as an end
view?
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I was hoping that cooling would not be an issue because I'll basically
be making a 4-1/2" long grooves, moving over about 1/8", and then
repeating for a total of 16 of these grooves. I can then cut off 1/4"
thick slices with my band saw. (The other alternative is to cut off
the 1/4" thick slices first and make the grooves in each piece). :-)
I would suggest that would be preferred, since that will let you
go a little too thick and make a nicer finish with the mill before you
turn it to mill the grooves.
As for the mill to use -- use a *brand-new* end mill for this so
it is at its sharpest, and later use those for metal working while you
move newer ones into the plastic milling game.
I guess my mini mill(with sharp 3/8" end mills) is the best machine
for the grooving job, out of the what I have. (I just have to get it
fixed first).
Yes -- that makes a difference.
You might, if you clamp the plastic to the mill's table with the
two sides to be grooved on front and back edges, try a 1/4" woodruff key
cutter (if you can find one that big) which would be closer to the
horizontal mill cutter which I said I would use by preference.
I have a lot of Delrin, which is also my favorite, but I like to save
it for the critical stuff, since it is not cheap. :-)
Understood. Compare it to Teflon. :-)
BTW. I use this chart to get an idea of the properties of the plastics
I tend to have:
http://www.machinist-materials.com/c...r_plastics.htm
Useful -- though I did not notice the change in dimensions when
exposed to water -- may have been there, I got tired of scrolling around
the page. A printed copy of the right size would be easier to work
with.
Good Luck,
DoN.
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