"Carl Ijames" wrote in message news
"Bob La Londe" wrote in message news
"Bob La Londe" wrote in message news
Looking for 3mm Teflon Coated Stainless Wire as a core for a mold I am
designing.

I checked McMaster and they topped out at 0.082 in. I'm looking for .118in
(3mm). Some of the lab and medical supplies go to .090 in, but that's still
too small. Suggestions?

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So far the best appearing solution is to get 3mm OD (2mm ID) tube and push
some 2mm wire thru it. If its tight, great. I can make a jig to hold the
tube straight during the process.
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So you need the overall od to be 3 mm, not 3 mm rod plus a teflon coating?
You don't say how long or how many, but if you need a tight grip between
teflon and SS you could use teflon heat shrink on SS rod, instead of pushing
on teflon tubing. If the length is short, shrink in batches in an oven.
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Yes 3mm net OD. It could vary a couple thousandths. I had considered
bending the assembly outside of the critical area to keep them together.
Maybe even use a crimp sleeve past the bend as I know how slippery teflon
is. For this application a net length of around 3 inches and about 20
pieces, but if I can make it work I would likely repeat this process for
other applications. The teflon is used as it does not wick heat away as
quickly as steel, the wire is because it needs to be fairly straight. 3mm
is the spec.

I've done similar core pins with 1/4 teflon rod and a 6/32 machine screw
threaded inside. It works. The casting fills, and the screw provides both
rigidity to the pin, and a place to pull with pliers from the casting.
Sometimes I can get away with stainless wire for pins, but when the
clearance between the core pin and the wall of the cavity gets to small the
heat sink ability of the wire/core is significant. Also, the teflon pulls
from the casting much easier than a steel or stainless steel pin. You can
coat steel pins with motor oil (it can take the heat) as a release, but it
leaves a residue that can make succeeding processes more difficult or
require a cleaning process. Graphite and talcum powder also work, but each
has its limitations.