Horizontal striations in groove

[electronrancher]

Here are some pics from a test cut. It is noisy, and I'm wondering if these striations are part of the cause.

Material is polycarbonate at 110F, tungsten stylus at ~20 degree angle, 3oz weight, light oil, and about 1W in the presto.

I am seeing roughly 4.3mil grooves with 0.71mil p-p displacement. I may drop some weight and add some power, but I'm scratching my head over the striations.

Sorry for the dirt on the lens, should probably clean that...

Hmm pics won't attach from this app, I will try to add them in an hour. Sorry!

[electronrancher]

1khz

IMAG0555.jpg

Closeup

IMAG0562.jpg

[piaptk]

I get similar lines in my grooves sometimes (not that many usually), but my noise floor is pretty low... Usually nothing more than a little grumbling that disappears one the audio comes in. Perhaps your playback needle is riding in the side of the groove... Have you tried gently nudging it over into the bottom of the groove?

[electronrancher]

Yep, I did some hoppin around and side pushing to make sure the playback stylus wasn't riding in the lands - I got a pretty bleepy/screechy version of the sound when it was out of the groove so I'm pretty sure it was riding ok. BUT... The groove is pretty wide, so I began wondering today if perhaps it was riding all the way down in the bottom.

I'm about to head out of town so I can't retry until next week, sadly. But my plan is to first back off of the weight a bit while keeping everything else the same. Then... try other stuff...

I'm debugging a couple of mixed things, trying to increase signal to noise..
1) Repetitive low frequency crunchies - definitely turntable rumble as it's much worse without the vintage cork mat. The bearing looked pretty new, but who knows. Motor mounts are vintage, but do still have some flex. And roller seems in really good condition, but I'm considering sending to Terry anyway. They will probably be replaced in that order, after replacing the vintage cork mat.
2) Overall white noise. This I don't know, and I'm currently blaming on the striations until it's proven or disproven. I used a petroleum/silicone oil which seemed to bead and not wet the surface, so I'll quit being a pansy and douse my lathe in Ronsonol on the next test. Kidding.
3) Some random, high frequency chirps. These pretty much went away after 5-10 minutes of cutting, so I called it "break-in". To me, it sounded somewhat like extra hard areas of PC that were chipping instead of embossing - like some random crystalline structure. Dunno, but it's not doing it now. I should try to take a scope picture of one of those sometime for science's sake.

Piaptk - I've heard your soundcloud samples, and they sound really good! If you have a random disc where you could throw up a "noise floor" sample, that would be awesome - give me something to strive towards, at least.

[tragwag]

hmmm. I usually cut about 2mil grooves or so when the noise floor is lowest.
don't quote me on that as my scope is only 40x

some of what you describe may just be the material flatness overall.
even blanks that look flat come up a bit, and so changes the depth ever so slightly.

your grooves look good with the sine tone, but what LPI is this?
for music of any sort of level and length (160 lpi and up), I don't think 4 mil grooves (for embossing) will work so well.

just my thoughts, though again trial and error is the only way with embossing.
often, I'll figure out a great system, come back the next day and it's nowhere near as good.
best of luck!

[electronrancher]

Thanks for the tips! It's 120 LPI