VMS70 Dash Pot. How do you run yours?

[concretecowboy71]

Lately, some of my masters have had a very quiet squeaking noise once every revolution. Today I worked all day chasing the issue down (changed belts, lubricated all points, changed stylus, checked radius and more) and after eliminating most everything it was suggested that I reset my dash pot and see if that was a factor.

I followed the factory instructions and after some trial and error, it appears that I finally found the problem.

My question is:

1) What oil do you use? I have been told there are at least two kinds that have been used (silicone and a mix of heavy and light petroleum oils). I have been also told not to use the silicone because it creeps into the head over time.

2) Where do you run your dash pot? Right now I seem to be getting good results about one half turn clockwise from fully open.

As always...thanks for your input. I hope this helps some poor soul save eight hours chasing down a noise that sounds like a cricket!

[Bonati]

I think the setting is likely different for every lathe. I had the same squeaking in the beginning too. I think mine is set somewhere in the middle. I'm using the light/heavy oil mixture. Never heard of the situation where the silicone would seep into the head - how would it get there?

[concretecowboy71]

I was told by two lathe repair guys (Al and Chris Muth) that the surface tension of the silicone allows it to "creep" over time out of the pot and down into the head where it makes a big mess.

That is why people stopped using it.

I thought that was pretty wild, kind of like "The Blob that ate my cutterhead"!

You are right about how each lathe is different, Even the oil or combination of oils can change how it is set.

I was wondering how people got to the point that works for them. Trial and error works, but takes time.

[Bonati]

Well those are the gurus, so it must be true. I took Al's advice on the oil mixture and the general position of the nut. I experimented a little bit but seemed to get it locked in pretty soon after.

[mossboss]

Singer Sewing machine oil works fine and its about a buck for the can
Whale based so temp variations do not affect it greatly
Its not hard to set it make sure there is oil in the pot a bit past the top where the little arm is mounted on
Just move the whole head suspension contraption with your hand two thumbs one at the top the other at the bottom, move it fully up and fully down a few times with a nice and easy even continuous pressure so a smooth movement results, that is so as to get any air trapped in there out, then adjust to suit
How?
Easy just push it up like suddenly with your index finger it should not move with a jerk it should resist the sudden push than move up The pot only works in the direction up
If it moves with a jerk there is air in there The golden rule is you cannot compress liquids only Air
A jerky movement indicates that it has air trapped in the pot
This oil density is more of a legend than fact any thin oil without air being trapped in there should work well and by the way where the hell did they get silicon oil back 40 years ago? from the space program?
And opcode the dash pot is checked every day and a few drops of oil on the slides every day, it takes about 1.5 minutes to do and it saves 8 hours of scratching around Remember that make a check list and follow it daily Easy
Cheers

[Techie]

When I had a Presto 6n, the manual said to use glycerine. Is that no longer considered a good idea?

[concretecowboy71]

Nobody has ever suggested that for a Neumann lathe so I cannot speak to that.

It seems that would be pretty thick.

[subkontrabob]

This oil density is more of a legend than fact any thin oil without air being trapped in there should work well and by the way where the hell did they get silicon oil back 40 years ago?

I'm using the light/heavy oil mixture.

I got a hint about the correct oil mixture from a guy who used to be the head of equipment acquisition at Finnish Broadcasting Studios. He bought a used lathe in the late sixties, and when on a business trip to Berlin (Finnish Broadcasting Company was a trusty Neumann client), asked for advice on his new "toy". They serviced his two R12 heads (standard groove), and told him how to get the proper mix for the dashpot.

You mix two kinds of oil. The correct viscosity can be determined by dipping a screwdriver or something similar in the mixture. If it flows down as a thin, continuos stream, you have the correct mixture. If the stream is interrupted and beads or drips develop, the mixture is wrong.

This piece of info came supposedly directly from the Neumann engineers....