[78-L] runout spirals

[Royal Pemberton]

No, those are called drive pin holes, and served only to prevent slippage of
discs while cutting.

On Sat, Oct 9, 2010 at 5:05 AM, Milan Milovanovic <
milanpmilovanovic4 at gmail.com> wrote:

> Are those eccentric grooves were cut by placing lacquer in those additional
> holes (1 or 3 of them) used for stabilizing locking blanks onto lathe mat
> when cutting? You can put cutting needle anywhere then and make just one
> simple revolution, and voila...
>
> Just a thought...
>
>
> ----- Original Message -----
> From: "Royal Pemberton" <ampex354 at gmail.com>
> To: "78-L Mail List" <78-l at klickitat.78online.com>
> Sent: Friday, October 08, 2010 7:06 PM
> Subject: Re: [78-L] runout spirals
>
>
> > I'd think that would be how a lot of eccentric grooves were cut, with the
> > disc offset.  The only mastering lathe I've ever seen, a Neumann AM 32,
> > actually had a latching arrangement on the underside of the turntable
> that
> > permitted offsetting it to permit cutting eccentric grooves.  (Once upon
> a
> > time, I tried to get the guy who owned the lathe to cut me a disc with an
> > eccentric groove at the end but he refused, citing the hassles of getting
> > the platter re-centred and perfectly balanced again....)
> >
> > On Fri, Oct 8, 2010 at 5:40 PM, Michael Shoshani
> > <mshoshani at sbcglobal.net>wrote:
> >
> >> On Fri, 2010-10-08 at 08:53 -0700, DAVID BURNHAM wrote:
> >>
> >> > There are two possibilities - either the recording
> >> > stylus, after the music is finished, is activated by a cam to go
> >> > through
> >> the
> >> > eccentric groove motion to create the trip groove, and then moved
> ahead
> >> > a
> >> > millimetre or so and so activated again, or, the recording stylus
> >> disengages and
> >> > a separate cutter, mounted on the same assembly is brought down to
> >> engrave the
> >> > trip eccentric.
> >>
> >> I'm thinking the separate machine theory as well, but here's the kink in
> >> the works: the eccentric grooves on VEs are different sizes. If the dead
> >> wax is larger, the eccentric pair is really large, but if the dead wax
> >> is small, the eccentric pair shrinks. If they used a cam on one of their
> >> machines, it would have to be adjustable in some way.
> >>
> >> Early Capitols and I believe some early Deccas are cut with an eccentric
> >> runout spiral. This would indicate shifting the wax or lacquer disc
> >> somewhat while the spiral and locked groove were being cut, I think...
> >>
> >> MS
> >>
> >>
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