From: Jim RabidWolf
To: 7x12minilathe@...
Sent: Sunday, March 04, 2007 2:59 PM
Subject: Re: [7x12minilathe] Way Lube, last post
I'm still using mobil 1 on the ways, however I have found an additive that
makes them so slick, the tailstock will not lock in place <G> After a bit
more testing, it may be offered for sale.
Rabid
Lubricity or as some call it "oiliness"! Of all the traits of a lubricant this is one that you rarely see a specification on. Usually from synthetic fluids suppliers but never from mineral oil suppliers. Unlike viscosity which is a function of the fluids internal interplay within itself, internal friction, lubricity defines how the lubricant interplays with the material it is applied to, external friction. From a tactile view point it is hard to distinguish. To quantify lubricity as a separate function, the additive must not interfere with the viscosity of the material it is added to. In other words the fluid, before and after addition, would need to display the same viscosity absolute (centipoises) as measured on something like a Brookfield Cone and Plate test rig, then show a lower sine of angle slip to proof a claim of greater lubricity. Years ago it was found that Wynn's friction proofing, which claimed greater lubricity, was not much more than kerosene which just reduced the viscosity of the base oil it was added too. Yes it provided a lower sine of slip but also reduced film strength significantly and greatly reduced viscosity and nobody at home knew the difference. The same effect could be simulated by going down one or two SAE grades or running the motor hotter by 20 to 30 degrees F.
Another "trick" used by oil suppliers is to play with the molecular weight via catalyst cracking operations or reforming, more or less molecular branching, or selectively placing the distribution curve of the fluid via distillation , thus altering the specific gravity. As the SAE and ISO rating systems are apparent viscosity systems their relationship to the absolute systems hinges on this factor. Apparent viscosity in centistokes (cST) relating to centipoises (cP), that is centistokes X specific gravity = centipoises. Centistokes or Saybolt Seconds are used as industry standards to classify a lubricant and if pumped or dripped the delivery system cares about its apparent nature but the lubricated surfaces proper only cares about the absolute value.
In a more simplistic layout, ways and slides use viscosity to dampen vibration "chatter" and provide dynamic braking to the system, along with mechanical considerations. An additive that provides lubricity at the expense of viscosity may improve the tactile "feel" while reducing the dampened features.
Keep us posted Rabid, I'm very interested in your project!
Marty
