How to cut sorbothane?


I recently read a glowing review of Herbie's Big Fat Discs, which are 5/16" thick by 1 5/16" diameter sorbothane discs. So, I did some research and I found a huge variety of sorbothane sheets available at McMaster-Carr. I bought a 12"x12" by 1/4" sheet of 40 durometer sorbothane for $29.

Does anyone have a clever and easy method for cutting discs out of this sheet other than scissors? I was thinking of a sharpened cookie cutter type thing as a tool which could be hammered down on the sorbothane, effectively cuttting a disc...

BTW, I can get 8 discs out of this $29 12"x12" sheet (with useful scrap left over), and 8 Herbie's Big Fat Discs would cost just under $90.
tvad
Sorbothane is a proprietary thermoset polyurethane formulation. They have a patent on the specific formulas, blend to the various durometers, and add modifiers for specific applications (chemical resistance, fire retardation, etc.). Several polyurethane blenders make similar products, Sorbothane is just marketed for vibration isolation and absorption applications.

Thermoset polyurethanes are an isocyanate and a polyol (resin and hardener) that are mixed together and allowed to set. They cannot be remelted, hence thermoset - not thermoplastic. Most specialty polyurethane manufacturers' have large drums of polyols, isocyanates, and the modifiers they use in their formulations, going from drum to drum by hand, creating the specific formulation of their products.

Within the same polyurethane product category, a change of durometer is often as simple as a change of one element in the hardener or mix ratio.

In other words, you wouldn't believe how simple it is to blend polyurethane compounds. We have several polyurethane mixes in our facility that produce the same "isolation effect". Sorbothane just found a modifier (probably a plasticizer) that they can sink their marketing teeth into, did the work to document the properties, and applied for a patent/s.

The point kinda is - each manufacturers' formulation will be slighty different (but patentable) leading to a very similar effect in material properties.

Sorry for answering a question that nobody really asked, but you happen to be talking about a subject I actually have a little knowledge in.(Now some bona-fide PhD Chemist/Audiophool is going to burn my noogies for opening my mouth and show me just how little I really know).

And yes, when I got around to it, I was going to put together isolation devices from the polyurethanes I work with and see if it works/helps.

Jim S.


Grant- i think that your idea of just cutting some squares or rectangles is the best solution. The cost of the proper tool is only viable if you are making dozens of discs. let us know how it sounds.
11-16-06: Swampwalker
Grant- i think that your idea of just cutting some squares or rectangles is the best solution. The cost of the proper tool is only viable if you are making dozens of discs. let us know how it sounds.
I believe you're right. If I happen to find a tool for $30 or so, I could conceivably make 36 discs out of the one sheet of sorbothane that I purchased for $35 shipped to me. That would more than make up for the cost of the tool.

I will let you know how it sounds. As I mentioned (I think), I plan to put them between the speaker modules of my VR4 loudspeakers. Others have commented that this makes a nice improvement.
i would think that it would work there. i have read that many folks tweak their VRs with some form of isolation btwn the cabinets.