Presto 1-D and 1-C cutter heads are frequently encountered on our lab bench for repair and restoration. Some are just regular repairs to original spec, others are rewound to a different impedance, but some undergo more comprehensive and exciting modifications!
We have previously examined modifications where a feedback system was added to a Neumann MS-52H and an Audax R-56 cutter head. This time, we shall discuss adding feedback to a Presto 1-D, which arrived with damaged coils.
This Neumann cutter head arrived as a particularly clean example, but in need of repair. The first obvious issue was that the coil was fried. The second issue was that the original stylus fitting was broken.
We recently had the pleasure of having Symatic over, from Bristol, UK, for a week of training on how to cut (and how not to cut) records.
Symatic runs Cut & Paste Records, a record label attracting some serious attention among skratchers, with high quality releases of skipless skratch samples, lock-groove tones, beats, and relevant music.
All Hardinge HLV and HLV-H variants feature a continuously variable speed drive to the spindle. It starts with a 3-phase, two speed squirrel cage induction motor, rated at 500 rpm and 1500 rpm nominal (less in practice, due to slip) at 50 Hz. This would be 600 rpm and 1800 rpm at 60 Hz.
Finding a Hardinge HLV can be challenging enough, especially if, like us, you happen to be located in Europe. At 1400 lbs, shipping and handling gets complicated. In a previous post, we described the joys of forklifting the beast onto a platform trolley (with suitable structural support added to the building), to get it to the workshop, though narrow corridors and doorways. Once there, it had to be lifted off the trolley and placed directly on the floor. With no chance of being able to drive the period-correct forklift truck into the shop, we had to get creative. A hydraulic engine hoist along with slings and tacks got the job done neatly. With the lathe on the floor and properly leveled, it was time to check it over, replacing, adjusting, lubricating and cleaning parts along the way!
The best finds always pop up in the summer, when everyone else is on holidays! Still, they are not always nearby or easy to deal with. When this 1954 Hardinge HLV precision toolroom lathe appeared on the horizon, it took all of 5 minutes to decide to go for it and one week of frantic international phone calls to organize everything. An engineer was sent to check it over, local transportation to an industrial machinery crating facility, international transportation, more local transportation and another week later it was finally in our yard!
Inspired by the toolposts used in metalworking lathes and improving upon the cutter head mounting system used by Neumann, the Type 6021 will accurately and rigidly hold any cutter head fitted with a suitable bar, including Neumann, Vinylium and FloKaSon heads, as well as any other head imaginable, through the use of our Series 1400 head mount adapter range.
Happy new year! Time to reveal what has been secretly developing in the lab throughout the past year: A stereophonic cutter head of an entirely unique design, invented by J. I. Agnew during his work with experimental transducers for measurement and testing purposes.
There is a long history of use of precious stones as industrial materials, from precision bearings to cutting tools, lapping compounds to grinding tools and several other specialised applications.
The recording of phonograph records is essentially a machining operation, performed by means of a machine tool called a disk recording lathe. A special cutting tool is used to cut a continuous spiral groove on the surface of a blank disk. This tool is called a disk recording stylus, or simply cutting stylus. The big difference to other forms of machining is that there is sonic information stored as modulation of the cut groove, which can be reproduced on another special machine, often called turntable or record player, or disk reproduction system.
In the previous episode, we had a look at taper shank stylus adapters and saw a vintage magnetic monophonic cutter head fitted to the AM44 lathe. The two are not normally compatible. Neumann lathe suspensions do not have the same mount as the suspensions of Presto, Fairchild, RCA and other lathes of the monophonic era, which were originally designed to accept such cutter heads.
But, in fact, almost any cutter head can be fitted to any lathe, as long as there is enough space for it to physically fit, by means of a suitable adapter. The eagle-eyed reader will probably have noticed that the cutter head mount on our prototype AM44 suspension is similar to, but not the same as, the mount used in Neumann suspension boxes. So, the adapter shown here was made specifically for our AM44 suspension unit.
Stereophonic cutter heads developed by Neumann are designed to accept a cutting stylus with a conical shank, resembling a micro-miniature version of a Morse Taper, a type of fitting frequently encountered in machine tools, especially metalworking lathes. Vinylium and FloKaSon cutter heads also adopted the same fitting for the sake of compatibility. But most other cutter heads, especially all those predating the stereophonic era, used long, thin cylindrical shanks, often with a flat machined on one side, to allow a set-screw to align the stylus and secure it in place.
Swiss Precision Engineering: The legendary Schaublin 102 precision lathe with parts of a Simonet lathe in the Agnew Analog laboratory! These pictures are from a 2016 restoration project, documented on the Agnew Analog website. Read the full report here: Schaublin 102 Swiss Precision Lathe Restoration
Back in 2015, we started a big lathe project, taking a beat-up Fairchild lathe from the 1930's, fitting it with an RCA cutter head, and eventually going full-on with a stereophonic feedback cutter head, vacuum clamp-down platter and automatically variable pitch.