Fixed Pitch Scully Lathe question

[mr_scratchy_esq]

Hello,

I will soon be the owner of an old Scully 501 lathe. Is there anyone on the board using a fixed pitch Scully? Aside from the inability to get longer cuts and maximize level, what (if any) are the sonic drawbacks to a fixed-pitch system. Will I really be at a disadvantage sonically even if I keep cuts on the short side (ie. 16 min a side for lps)? Has anyone on the board made the modification from fixed to variable pitch? FWIW, I am acquiring this lathe as part of a package deal that includes a defunct recording studio and a newly restored record pressing plant.

Thanks,
Bill

[Steve E.]

I don't know about Scully lathes per se, but check out the charts I'm futzing with in this thread:

https://lathetrolls.com/viewtopic.php?t=824

I think you should be able to get 16 minutes or so per side using a fixed pitch of 160 lpi, which people are telling me should also get you decent sound. I have not done this yet, because I have not had my 160 feed screw made.

Kim Gutzke of Custom Records told me he is developing some sort of variable pitch system that can go on an existing lathe turntable (hope I am remembering that right). Look for his info in the top link of the "Resources" section of this site.

[cuttercollector]

My friend's Scully has had most of the pitch drive system gutted.
The leadscrew shaft is extended outside the main casting and there is a pulley. This pulley in his configuration was being driven by a small DC motor with a variable voltage supply. He was able to get good results for variable pitch but had some issues with being able to "overclock" the motor with high enough voltage for legitimate lead in and lead out grooves and also have it run slowly and consistantly enough for even groove spacing at high lines per inch.
My point is, varying the pitch does not always have to be a matter of changing the leadscrew. You can change the drive ratio via a pulley tree system (like a drill press) as on some Presto units, vary the speed of a pitch drive motor etc. The hardest ones to vary are directly gear driven off the turntable. There, changing the leadscrew might be the best choice.

[cuttercollector]

One more question. How does lines per inch pitch directly affect sound quality?
Only thing I can think of is if you cut too fine a pitch you have to limit bass and level more and more to keep the grooves from running into each other. But that is something you choose to modify in response to time constraints. You can always not limit bass or level and cut a wider groove pitch. That is why automated variable pitch systems were developed.

[jtransition]

I cut fixed pitch for years and had no problem getting 20 mins on a side.
Jason

[diamone]

Well, just as any mastering engineer knows, not only do you have to reduce the level to cut longer sides, you also have to take the depth-of-cut back from 100-120 on a 45 or 90-100 on an LP back down to maybe 50, 60, or 70 depending on which fixed pitch you use.

You can look at any number of especially independent`deep-grooved' releases which border on having too deep of a cut for the pitch. As we all know, one can increase the depth of cut only to the point of ``land'' disappearance, but no farther, as grooves will then skip.

[kgutzke]

Kim Gutzke of Custom Records told me he is developing some sort of variable pitch system that can go on an existing lathe turntable (hope I am remembering that right). Look for his info in the top link of the "Resources" section of this site.

Kim here. Not so much a variable system by itself - but more so a complete overhead lathe with auto pitch/depth. I'm working with an "engineer" to get something started - but no one hold your breath )