[78-L] runout spirals

[neechevoneeznayou at gmail.com]

This is getting a little OT but some of you who attended the ARSC 
Conference in 1997 (?) in Syracuse, may remember that in their control 
room they had a lacquer on their SP 15 using the drive hole as a center 
hole. It caught the attention of many!

joe salerno


On 10/9/2010 1:30 AM, Michael Biel wrote:
>
>
>
> 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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