On Nov 16, 12:11 am, "DoN. Nichols" wrote:
On 2011-11-15, Searcher7 wrote:

On Nov 15, 12:24 am, "DoN. Nichols" wrote:
On 2011-11-15, Searcher7 wrote:

Yes. I may lay a 1/16" Nitrile or Styrene Butadiene/Natural Rubber
blend pad in between the block and contacts to keep the contact
consistent between all of contacts of two opposing blocks during heavy
vibration.

That -- or bend the contacts so they bow up in the middle of
their length.

Well, if the contacts were to be secured by only one end, then I'd
just let them bounce like a diving board, resulting in less metal
fatigue. But, the wiping action I'm incorporating must allow for both
directions across the contacts, which is why both ends of each contact
has to be secured.

The *structure* the contact blocks will be permanently attached to
will be wood, which must come together tightly and locked into place.
Something like rubber will account for any expansion/contraction of
the structure under conditions of varying humidity.

O.K. Very different from what I was interpreting your text as
saying. Be sure to view this with a fixed pitch font (like Courier) to
keep the drawing from being distorted

/ / /
/ / / //
/ / / ///
+---------------+ / ///
| |/ ///
| | ///
| | ///
| |///
| |/
+---------------+

As I was drawing it, the (now added) diagonal lines would go
along the 4.5" length, the 3/4" width would be the horizontal dimension,
and the 1/4" would be the vertical dimension -- giving only room for a
single strip on each side.

Obviously not what you intended to say.

Ok. The 3-D image makes things clearer.

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.

I figure I can use a hand file to clean up if needed.

You may want to make something too thick and finish with the
mill (or a metalworking shaper if you had one).

I'm not averse to hand tools. :-) (Which is preferable considering my
present living environment). :-)

A Woodruff key cutter is normally used to make a cut in the side
of a shaft which is like a ')' in profile, into which a Woodruff key
(like a slice off the edge of a coin) is placed, and part of it projects
above the shaft to engage a groove in the pulley or gear on the shaft to
prevent them slipping around the shaft.

However -- the cutter is *not* right for cutting the grooves in
the direction you want. It does not have a long enough shank to reach
along your shaft in the 4-1/2" dimension. I was assuming that the
groove was parallel to the 4-1/2" dimension, in which case a Woodruff
key cutter could do a nice job on either side of a piece of plastic
clamped down to the table -- *not* in a vise.

Ok. But I'll keep those in mind when I have to make a keyway in
something like a motor shaft.

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. :-)

I had some opportunities to pick some up relatively cheap, but didn't
foresee any use for it at the time. :-)

Too good for your task, unless you need the low friction
features of it. You aren't working with high frequencies, and certainly
not with high voltages (2 kV to maybe 60 kV. :-)

Nylon should be fine for what you are doing.

Yes. And Delrin has always been good enough for those low friction
needs or for when dimensional stability is needed.

Thanks a lot.

Darren Harris
Staten Island, New York.