The Secret Society of Lathe Trolls

OLDLEE · Joined: 12 Nov 2007 Posts: 14 Location: Ontario Canada

Does anyone know what type of plastic was used for the green Sound Scriber blanks, which work by embossing a modulated groove?
I think thin sheets of Lexan will work as a substitute (it won't break but it takes scratches very easily), but it would be good to know the type of original plastic, in case one can still get it.
Readers of this forum will probably know that the Wagner Micro-disc used the same process.
Thanks from a new member.

grooveguy · Joined: 22 Jun 2006 Posts: 40

Not sure about the Soundscriber blanks; have a bunch of them, however. When they burn... one of the best ID tests... they smell like styrene plastic.

You are right, the Wagner-Nichols machine was quite similar. It had a following in the late 1940s, written-up in Audio Engineering magazine. Could e-mail a scan if you are interested.

I plan to make some exhaustive tests re: sound embossing. With bonafide cutting styli getting harder and harder to find or resharpen, an embossing scheme might have merits for us experimenters. If you have ideas, please share. In particular, if a spherical stylus is used for embossing, what's a good angle? Obviously a vertical stylus will simply tear the suface of the disc. If you take a relatively good stellite or steel cutting stylus and chuck it up backward, it will indent a nice groove in something like a CD. It would be interesting to know the physics of embossing; that is, what the virtual point-of-contact with the groove actually is. I have a feeling that the HF response is not nearly as good as with a chisel-type stylus, but at 78rpm decent results might be achieved.

OLDLEE · Joined: 12 Nov 2007 Posts: 14 Location: Ontario Canada

Thanks, Groove-Guy, for the info. The clue about smelling like burning styrene is very useful...I wasn't sure they had styrene back then, but the discs might have been made of a precursor plastic. I am assuming that the embossing stylus point is like a very tiny ball...will have to check on the Wagner machine. Thanks again.

OLDLEE · Joined: 12 Nov 2007 Posts: 14 Location: Ontario Canada

Memo to Grooveguy: I looked at a Wagner embossing needle under a microscope and it's very much like an LP sapphire phono needle - not a ball as I had assumed. I suppose this is because the point provides a lot more pounds-per-sq-inch pressure for good embossing, but without tearing. People say the Soundscriber stylus is ball-shaped, however.