Re: [ARSCLIST] ET groove cutting ( was "More about ET preservation", was "Comparable collections anywhere?")

[George Brock-Nannestad <pattac@xxxxxxxx>]

From: Patent Tactics, George Brock-Nannestad

Eric Jacobs wrote:


> Graham Newton wrote:
> 
> > The BIGGEST problem was that most people trying to cut a disc NEVER read
> > the  "how to " manual and didn't have the foggiest idea of how to do it right.
> > They cut using chipped styli, worn styli .......................  The resultant
> > grooves bore the scars of the mistreatment and that consequently, is what
> you often see when looking at a groove under a microscope.
> 
> Thanks so much for that bit of history.
> 
> Actually, all the variations that I see in the grooves that I was refering to
> are on professionally cut studio lacquers, or on lacquer dubs.  I just wish I
> knew what aspect of the cutting process failed to create the groove
> distortions I see.
> 
> I'd like to be able to name these distortions more accurately in my groove
> condition descriptions that go into the technical metadata.
> 
> For example, sometimes the bottom of the groove is very rough - it almost
> looks scaly.  It seems that either the cutter wasn't hot enough or the angle
> was wrong, but I have no idea really what happened.
> 
> Other times, the groove bottom has a bumpy quality, almost like a smooth-ish
> lava flow.  The walls will still look just fine, but these are suprisingly
> noisy.
> 
> Other times, the bottom of the groove will be striated - I can't think of a
> stylus that would create that sort of wear pattern on a flat groove bottom. I
> have to assume that the cutter was perhaps worn, but maybe it's something
> else?
> 
> Those are some of the things I'm curious about.

----- I think that you need to get practical experience of cutting grooves 
yourself. I have had 78 rpm cutting equipment since 1990 and have 
experimented with a number of parameters. Fortunately I had an assignment to 
cut records (once I trusted myself), so someone else paid for the surplus of 
lacquers I have. They are quite expensive. However, you may use just 10 
revolutions on the pristine lacquer for each test, so you will make room for 
a fair number of tests per disc. You will enjoy avoiding having the swarf 
getting caught in the stylus (vacuum was only for expensive equipment), and 
the respect for cutting engineers increases as your own skill increases. Be 
careful, cutting is addictive, unless you have to make a living out of it!

----- your phenomena could partly be explained by chipped cutting stylii - 
striations are typical of that, and sapphire did chip if you hit something 
with them. Steel cutters were also used, but they gradually wear so that the 
edges get rounded, increasing noise. The wear was caused by remaining 
extremely fine grit in the lacquer, remaining, although the liquid was very 
carefully filtered to avoid that. They did not generally use heated cutting 
stylii at that time.

Kind regards,


George