On Thu, 14 Jan 2016 17:11:25 -0800, Jeff Liebermann
wrote:

On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
wrote:

Anyone any such experience here?
I know it's a long shot.

Google for "mold your own rubber parts" or "cast your own rubber
parts". Lots of lousy videos on YouTube on how to mold rubber parts.
I use Plaster of Paris for the mold, Devcon Flexane 94 Liquid 15250
two part urethane rubber
http://www.devcon.com/products/products.cfm?family=Flexane%C2%AE%2094%20Liquid
http://www.amazon.com/Devcon-15250-Black-Flexane-Liquid/dp/B00065TLJK
and Vaseline or silicon grease for mold release. Careful when storing
the stuff as the stuff in the bottle attacks the bottle and causes it
to leak. It cures in 10-15 mins, so be prepared to work fast.
Although it's made for making flex molds, it's also the right stuff
for making fairly hard rubber buttons, gaskets, shock mounts, seals,
etc.

Oops. The Devcon Flexane 94 is probably too hard and stiff for your
rubber button that has to bend and act as a spring:
http://oi65.tinypic.com/14xdmo3.jpg
Something more like RTV (silicone rubber) will be more flexible. I
have a Shore A Durometer (rubber hardness meter) and can measure a few
random rubber buttons and see what's appropriate. Well, the assorted
TV remote controls run 53 to 60. Various other rubber buttons vary
from 50 to 65. All my music keyboards have hard plastic buttons, so
that's not going to work.

I found a part I had made using Flexane 94, which shows 85, so that's
much to hard to flex. I don't have something handy that will work,
but I'll do some catalog searching this weekend. Offhand, I would
suspect that bathroom caulk, rain gutter seal, or other commonly
available silicone rubber compound might work but might also be too
soft (typically 25 to 30 durometers). Structural silicone might be
harder. Digging:
http://www.siliconeforbuilding.com/pdf/structuralglazing/Data_Sheet_SSG4000_UltraGlaze.pdf
Argh... only 39.

These might help:
"Using Silicone Caulk as a Mold Material"
http://forums.gardenweb.com/discussions/1472166/using-silicone-caulk-as-a-mold-material

Durometer Hardness Scales:
http://www.paramountind.com/pdfs/paramount_durometer_scale_guide.pdf

MasterBond Adhesive hardness:
http://www.masterbond.com/properties/hardness


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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