[78-L] runout spirals

[Milan Milovanovic]

OK, probably there should be an answer to how they did it...

Maybe later, in factory, right before electroplating?


----- Original Message ----- 
From: "Michael Biel" <mbiel at mbiel.com>
To: "78-L Mail List" <78-l at klickitat.78online.com>
Sent: Saturday, October 09, 2010 8:30 AM
Subject: Re: [78-L] runout spirals


>
>
>
> From: Royal Pemberton <ampex354 at gmail.com>
>
>
>> No, those are called drive pin holes, and served only to
>> prevent slippage of discs while cutting.
>
> If you tried cutting a lead out circle with the disc in a driving hole
> you will find that the swing of the eccentric is HUGE!!!!  Plus the
> cutting of eccentric lead outs predates the use of lacquers by well over
> a decade.  And modern lacquers no longer have the driving holes because
> modern lathes use vacuum suction to hold the disc to the turntable.
>
> Mike Biel  mbiel at mbiel.com
>
>
> 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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