It started life in the 1940's as a completely manual machine. A sturdy design, capable of very decent results, these lathes were extensively used across the USA and other parts of the world for several decades. Many are still in operation today. In the original condition, they were quite limited in what they could do. But, as with most good lathes, they can take a lot of modification and improvement.
Eric took it apart and basically started from scratch, replacing worn out parts, having a lot of custom parts made, and installing state-of-the-art components, turning this old Scully into one of the finest disk recording lathes in the world.
A substantial aluminum casting with a gigantic carriage arm, this machine was designed to hold the heavy American cutterheads, such as the Westrex 3D. Massive shafting and precise gearing hides within the lathe bed.
Originally the operator had a choice of seven cutting pitches from 88 to 130 LPI, outside-in or inside-out.
Scully lathes can be greatly improved in this respect, so Eric went for a Pitch13 automatic variable pitch and groove depth system.
The other weakness of the vintage Scully machines was the original platter, with cork on top. It was never as precise as it could have been, and the cork introduces a resilience which has proved undesirable over the years. Later Scully lathes came with a greatly improved platter, but Neumann machines were superior in this respect.
Neumann vacuum platters have been fitted to Scully lathes before, but they are now becoming rather rare.
So, Eric turned to J. I. Agnew, known for his work in heavily customised lathes, who came up with the ideal solution: A custom vacuum platter, machined from a special aluminium alloy, normally used in the aerospace industry, along with a custom subplatter, designed to fit the Scully lathe center bearing. The subplatter allows precise adjustment of the platter to extreme precision, using a system similar to the one found on Neumann lathes.
Machining the platter at the Agnew Analog shop.
Drilling and tapping the subplatter.
Testing the fit.
Machining the vacuum spindle.
Trying out the concept on our workshop testbed, a Neumann based AM44 lathe. The test cuts were outstanding, this platter is also great for Neumann lathes! Next step, fitting the entire assembly on the Scully lathe!
The first attempt resulted in the platter sitting a bit too high. The eagle-eyed reader among you will have noticed the original A&M / Bernie Grundman suspension unit, one of only five ever made! This unit allows electronic groove depth control and can actually float a Westrex head. As in, no advance ball needed!
Adjusting the platter runout, using a dial indicator. Hang the Westrex cutter head, tune in, turn on...
and cut some amazing records!
Many thanks to Eric Conn from Independent Mastering for his awesome pictures!