The Secret Society of Lathe Trolls

Bratwurst · Joined: 01 Feb 2008 Posts: 22

Ahoi, I'm trying to work out the depth of cut here. I've read in the recent post on rejuvinating a lathe that the chip should be thin like hair and straight and shiny (at least for a silent cut). The chip I'm getting is kinky. The same article says this is indicative of too much weight. Any less weight and my play stylus fails to track the groove and I get "bald spots" on flexi discs.

I don't have a way to measure the exact weight I'm using, just using the chip and the sound as indications. Although it seems like depth doesn't affect the surface noise too much.

Any takers?

JayDC · Posted: Thu May 01, 2008 3:52 am Post subject:

what are you cutting, pvc or acetate?.. I think the article was talking about acetate. If you not using acetate, then your chip will be different.

If your using acetate, check cutting angle, depth, and the age of the acetate. The older discs you'll find on ebay are usually pretty old, and hard.

Try fresh new acetate..

blacknwhite · Joined: 24 Apr 2008 Posts: 50

Cool title. Agreed, most likely freshness of blanks. If that doesn't work...

Have you considered adding an advance ball? If you're cutting on not-perfectly-flat blanks & have had enough luck with mechanics in the past that you'd not be afraid of ruining your cutting gear (assuming you're not working on a stereo Westrex), you could add one: Just requires any polished small rounded smooth surface.

From 1929, from "free patents online" site...

http://home.nc.rr.com/goodmusic/1929_cutter_head_advance_ball_patent_1874101.pdf

Also, there are articles on the forum for DIY stylus heating, but must be sure your head can take it (heat will RUIN a chrystal head; for magnetics, old rubber parts close to heat transmission may require replacement w/ more modern heat resistent neoprene rubber; metal cutting stylii might need insulation from heater wire with a shank coating of high-temp auto engine enamel; etc)

- Bob

Bratwurst · Joined: 01 Feb 2008 Posts: 22

Well, I'm not sure on several of these things... I *think* the blanks are some kind of pvc... I bought them with the lathe and I don't know what/how old they are... not decades though. Smile

The discs are like sheets of acrylic cut into circles... could they be just acrylic? They are fairly soft... I'm thinking lexan or similar. (see my dumbass replies about souri's blanks)

I'm using a vinylrecorder which has stylus heating. The heating electronics don't work, so I'm hooking it up to an external power supply. When using that, the chip just sticks to the stylus and makes a crystal glob. So I figure I'd better get a decent unheated cut before attempting with heat.

An advance ball is a good idear- I'll look into that...

cutting angle- I've read everything from "don't go past 5deg, foo!" to up to 18deg... since playback stylus is 15deg, I'm guessing the 18deg makes more sense, but it looks pretty extreme, so haven't tried that much yet- just a couple degrees. vertical makes the awesome demonic screetching sound. I love it, but it can't be good.

My stylus is taking a BEATING haha

JayDC · Posted: Thu May 01, 2008 6:39 pm Post subject:

Bratwurst · Joined: 01 Feb 2008 Posts: 22

12vac! I have a variac hooked up to it. I blasted it at 10v and it made the wire explode into lava. I was scared for my beautiful face. I set it at a conservative 2v after that. maybe I will try another power supply Smile

The wire coil I have is only about 3ohms of resistance. I don't know what the impedance would be though as it's coiled about 6 times. But with just pure ohmic resistance, I should have had about 3a through at 10v. less than an amp at 2v. The impedance would have lowered this some as well. maybe this variac is wack.

JayDC · Posted: Thu May 01, 2008 9:22 pm Post subject:

HOW MANY AMPS?????? a couple of mah should do it..

Bratwurst · Joined: 01 Feb 2008 Posts: 22

haha wow I thought that was a dangerous amount when I read it. Vinylrecorder makes these machines strong like ox. I have done everything in my power to kill it so far.

of course, I cannot find the source that said up to 5.5 amps.

Maybe he should call his machine "The Rasputin".

motorino · Joined: 24 Aug 2005 Posts: 190

hi folks!

i use that circuit

[URL=http://g.imageshack.us/g.php?h=167&i=heatingxw0.jpg][IMG]http://img167.imageshack.us/img167/50

i use 350 miliamperes + - for cut lacquers

BE CAREFUL!!! use a miliamperimeter, and before conect to the stylus try short the output and measuring the miliamperes with the variable resistor

The regulator lm317 work hot, use a heatskin, the big resistor 20 ohmn 10 wats work hot too.......be careful

MEGAMIKE · Posted: Sun May 04, 2008 1:48 am Post subject:

hi
i have vinlyrecorder and i never use heated stylus....
rarely.... if that....
_________________
seas of cut grooves

lester · Joined: 08 Feb 2007 Posts: 31 Location: belgium

Hi Megamike,

that's strange...don't you have got a lot of background noise then?!
I always heat the stylus upto +/- 30! If i don't heat it, i got crazy noise!!
_________________
diamonds are forever?! What a joke! Wink

bancho · Posted: Mon May 05, 2008 5:58 am Post subject:

Hey motorino!

What kind of heating wire do you use (length, diameter...)?
What is the resistance of the heating wire you use it that circuit?

motorino · Joined: 24 Aug 2005 Posts: 190

i use transco and adamant styluses in my lathe, with her original heating coil..

i believe all heating coils have very low impedance

i use that circuit ever with miliamperimeter, and work very good, 350-400 ma its ok

andybee · Joined: 14 Aug 2006 Posts: 63

simple thing:
pvc blanks are heated with lamp, so you don´t need heating wire.
laquer discs can also be heated with lamp.
lamp need much more power than a 5V/0.5A wire heating.

Bratwurst · Joined: 01 Feb 2008 Posts: 22

Thanks everyone for the help. The schematic was especially useful motorino.
I'm going to make it today.

Dub Studio · Joined: 20 Jun 2006 Posts: 49 Location: Bristol

An easy way to measure the depth of the groove is to measure the width of it and divide that by two. You can get eyepieces for microscopes (ideally x40 or more) that enable you to measure small fractions of a millimeter.

You definitely need to get a way to measure the weight of the head on a vinylrecorder, because it really affects the cut. Even if you find a setting you like by chance, different plates have different thicknesses which will affect the angle and therefore the weight of the head, so you need to be able to make small accurately-measured adjustments as and when you need them. A 100g lab scale works fine for me.

The other thing to remember is that the angle of the stylus can affect the downward force acting on the plate, so the larger the angle the less weight is needed. At 15 degrees I use about 20g, and at 0 degrees I would use about 30-35g, although I seldom cut at this angle. Heating makes a bit of difference to the depth but not as much as the other two factors I find, but it does make a difference to surface noise.

Whenever I set up I do the following:

1) set the angle of the stylus to 15 degrees
2) check the suction tube is about 1 or 2mm away from the surface of the plate, and 1 or 2mm away from the stylus (when its lowered onto the plate)
3) adjust the weight to about 20g
4) try cutting a few grooves and listen to the surface noise with no heat, turn the heat up until the noise improves (sometimes it gets worse before it gets better)
5) If you need to adjust the angle, then you need to adjust the weight again (that's why its best to do it in this order)

I am not saying this is guaranteed to work for you, but its a ball park setup, and the final setup must be trial end error. If you are trying to alter the depth of the cut using stylus heating alone you are probably barking up the wrong tree. Try different weights (and angles if you have to) without heat until you get close to what you want and then fine tune with the heat.

You might need to heat the plate a fair bit on a cold day, and just a touch on a warm day, but again trial and error is the key, and the weight and angle are more important to get right. A little heat can help a bit, but too much can be catastrophic!

One other thing, if you are using an old stylus, you will never get a clean deep cut no matter what combo of weight, heat and angle.