This is where record cutters raise questions about cutting, and trade wisdom and experiment results. We love Scully, Neumann, Presto, & Rek-O-Kut lathes and Wilcox-Gay Recordios (among others). We are excited by the various modern pro and semi-pro systems, too, in production and development. We use strange, extinct disc-based dictation machines. And other stuff, too.
The more I diddle around with these the more questions I discover. Didn't consider myself a "newbie" as I was cutting records on a Recordio 40 years ago, but now that I strive for better quality, I have these questions. I've moved past the Recordio to Presto and Rekokut.
1. I have a couple brand new styli from Apollo. Would it be my guess that these are cutting modern microgroove rather than standard grooves? I have been using some NOS Presto sapphire 604-A styli with better results than I've been able to get with the new ones, but it may because I'm being overly cautious with my adjustments on the new ones. I have a half dozen or so, new in the boxes, of the Presto styli, one box of which is stamped "microgroove" on the side making me think the others are standard. Am I correct assuming the new ones are all microgroove? It would only make sense.
2. None of my machines are set up for stylus heat. I'm presently still messing around with my Presto J5, and getting some acceptable results. But I've noticed many with online videos using various types of lamps to warm their blanks, either before putting them on the machine, or with a lamp near the platter to keep them warm while cutting. I recall one mentioning 100 degrees (F) was about right. Now, I haven't done any real scientific testing, but it's usually about 65 degrees in the room where I'm cutting. If I notice the heat come on (old fashioned water rads from 100 years ago) I will set a blank over the radiator until it feels warm, then cut it, and I do notice a reduction in surface noise and the cut seems smoother and the swarf more cooperative. Is the heating lamp idea a good plan? Seems to me, yes.
3. And this could be more of a theory discussion than practical. I have a nice Rekokut machine with the overhead linear cutter. I recall someone mentioning that these are better because the stylus remains properly positioned as it cuts rather than in an arc. And I remember the popular linear tracking turntables of the 70's and 80's that bragged how they track the LP record the way they were cut for best reproduction. BUT, I've never seen a 78 turntable from the 40's, 50's, 60's that have a linear tracking playback tone arm. Wouldn't it actually be better to cut with a fan (arm) style cutting movement rather than linear? Then the cut groove would be created more like a typical player would play it. Just pondering. I have yet to even plug in the Rekokut, although when I purchased it a few months ago I was assured it was operating perfectly and the artist (and I do mean artist) I purchased it from actually had his own "tech" who maintained it. It "appears" perfect.
4 Bonus question. My J5 has an Audax head on it. Gib rebuilt it for me. I imagine there are other cutting heads from which I can expect better fidelity and greater frequency range? Or are they all about the same? I'm presently driving it with a 70's era stereo receiver, using the meter in the Presto (the meter is in the circuit to the head when you use the external input socket) so I set the level correctly. I have a nice Grommes LJ5 (I might have those characters in the wrong order lol) mono tube amp from the 50's that I intend to try driving it with as well.
re:#3 I used to think the same thing - if most players track on an arc, why is linear better? The cutting stylus is not round, but chisel shaped with facets carefully designed to cut and polish a perfect groove. When a cutter moves in an arc across the disc, the chisel shape of the cutting stylus does not cut a symmetrical groove, except for at one point where it happens to be perfectly positioned. The more it strays from perpendicular, the more distorted or deformed the cut groove becomes. Towards the center of the disc, it's compounded by the fact that the linear speed of the disc is slower, the grooves become cramped, and you lose high frequencies. Not directly related to cutting in the arc, but it's one more thing to compromise fidelity. I hope my non-technical layman explanation helps.
Also - I dont' know of any new cutter that cuts 78 grooves. A new cutter would be microgroove.