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Greases and Lubrication

Modified on 2008/04/12 01:07 by Dan McCallum Categorized as Bearings, Maintenance, Restoration Topics

Grease for Machinery

Introduction to Grease

All greases start with an oil base stock and then add thickeners. The most common base is an ISO-220 stabilized oil. The most popular thickeners are metallic "soaps". Some of them are lithium, calcium, molybdenum, and boron. The metallic particles are made into a soap through a process call "saponification". Other thickeners used are microgel clays and polyurea, which are usually for specialized applications. NLGI (National Lubricating Grease Institute) is the most common classification system in use today. Grease thickness grades are from an NLGI of "000" which is pourable to a "6" which comes in brick form. NLGI grades do not overlap and there are companies that offer some greases in half grades ( NLGI 1.5). There is also an NLGI service classification that was developed for the automotive industry. Supposedly, they are working at an industrial equivalent to ASTM D-4950 which is the automotive standard.

Automotive greases and industrial greases are not equal. Many of the automotive greases have anti-wear additives that are made from polysulfides and/or chlorinated esters. These additives will attack "red metals" (copper) and will pit bronze and many brass alloys. Don't use automotive lubricants in machine tools or woodworking machines!

Lithium thickened grease is by far the most popular in use. Good for most applications and takes a fair amount of heat. Calcium is probably second in use. Calcium thickened grease tends to be a little more stable (stays mixed better) and can handle moisture better, but will not take much heat. Most electric motors and electro-mechanical assemblies are assembled with calcium thickened grease and not the "white lithium" that many claim. Then you go to molybdenum disulfide which has better temperature handling capabilities but is more expensive and should not be used around brass or bronze bearings.

Almost all of the "gun grease" is an NLGI #2. Lower numbered greases are used in gear boxes, central lube systems, and cartridge spindle assemblies. There are reasons for thinner greases and most of them are very valid. Just because a machine has a zerk on it, does not mean it takes #2! The manual is still the best place to look (assuming you can find one!) {Reference:|}

Grease Selection

For grease it seems that picking your favorite NLGI 1 grease should do. If you are starting fresh a synthetic NLGI 1 grease might be a good choice, in my opinion. If you are adding grease to a machine with an unknown lubrication history it’s a bit trickier. The consensus is that there is no known universally compatible grease, many grease types are incompatible with each other, and on an old machine, you usually have no idea what was used in the past. Mixing incompatible greases can soften one or both of the greases. Does this matter? Might. Ideal is to start with a clean, non-greased bearing. {Reference:|}

Chevron SRI grease is used/recommended by just about all motor manufacturers for ball bearing use. HOWEVER, since Chevron SRI is a Polyurea based grease, it can have compatibility problems with other greases. Industry recommends flushing out all old grease before re-greasing with a polyurea (Chevron CRI) grease. As to how much to add, most motors are OVER greased. One or two "shots" from a grease gun is all (about 2 teaspoons). Once a year greasing is way more than most applications need. Example, for new motors, Baldor recommends greasing motor bearings every 5,000 hours of operation (3600rpm) or 12,000 hours (1800rpm). At work, a belt driven, 15hp blower motor that runs 24/7 is greased just once a year. Motor has been in service 6+ years now no failure (~48,000 hours of use). I disagree with adding grease until it comes out when greasing a motor. Bob is right about removing the drain plug but, most (including maint. crew at work) don't bother to remove the drain plug to allow excess grease out. With new motors there is plenty of empty room and no grease will come out of the drain for many greasings. OVER GREASING damages more MOTORS than under greasing. {Reference:|}

Oil for Machinery

The following oils would probably cover most OWWM applications.

Velocite #6ISO - 10
Velocite #10ISO -22
Vactra #1ISO - 32SAE -10
Vactra #2ISO - 68SAE- 30
Vactra #4ISO -220SAE- 90
DTE 24ISO- 32SAE -10
DTE 25ISO- 46SAE- 15
DTE 26ISO- 68SAE- 20
DTE lightISO- 32SAE- 10

Other recommendations seem less clear. For example, for Oliver machines with open, oil bath bearings, speeds < 4,000 rpm, Dev and others have recommended DTE light or Vactra #1, both ISO 32 oils. Oliver literature recommends Vactra heavy medium oil. Vactra heavy medium oil seems to translates to Vactra #2 an ISO of 68. This comes from the Mobil literature and the PM site. I’m using Vactra #2 for my 116d and 166.{Reference:|}

ISO Viscosity Classification System

Many petroleum products are graded according to the ISO Viscosity Classification System, approved by the international standards organization (ISO). Each ISO viscosity grade number corresponds to the mid-point of a viscosity range expressed in centistokes(cSt) at 40 deg C. For example, a lubricant with an ISO grade of 32 has a viscosity within the range of 28.8-35.2, the midpoint of which is 32.

The lower the ISO grade number, the lighter weight (thinner) the oil will be. For comparison purposes, a "30 Weight" motor oil would have an ISO grade of about ISO-100.

Oil for Babbitt Bearings

There are about as many opinions as to what kind of oil should be used for babbitt bearings as there are people using babbitt bearings. The general consensus on what kind of oil to use is that it is really not that important - what is important is that the operator is using some kind of oil on the bearings.

Most old literature suggest that babbitt bearings be oiled with a "light machine oil". Oils with an . Any kind of light weight spindle oil between ISO-10 to ISO-68 should work fine. With that said, here is some specific information on oils used with Babbitt.

Way Lubes

The most recognized name is probably Mobil Vactra #2. Way lubes are formulated with tacifiers and EP (extreme pressure) additives to handle linear movements. The do work in some low speed bearing applications. Mobil changed the formulation of Vactra about 10 years ago at the request of the metal working industry so that the oil was more compatable with synthetic and semi-synthetic coolants. The printing industry complained and the old Vactra is available as Vacuoline. The generic name for Vactra #2 is; ISO-68 medium way oil.{reference:|}

Spindle Oils

Bearing and spindle oils and greases get more confusing. When somebody asks me to spec a spindle oil for them, I always ask, what's max RPM, what RPM do you run at most of the time, and what type of bearings, how are the bearings lubed, and what does the factory reccommend? Most of the time, I will get them a generic unless they ask for a specific brand. These generics are usually a R&O (rust & oxidation inhibited) stabilized, hydraulic recirculating oil, like Mobil DTE.{reference:|}

Spindle Grease

Generally speaking, babbitt bearings should not be lubricated with grease. Grease will not properly lubricate a spindle running at high speed on Babbitt. With that said, some slow speed babbitt bearings will operate fine with grease. However, do not assume that just because the babbitt bearings on your machine were acquired with grease fittings that the machine was intended to run on grease. Many times, unknowing machine owners will insert a few grease fittings on a machine, give it a squirt of grease from to time and "let her run". Unless you have documentation from the manufacturer that a babbitt bearing was intended to run with grease, it is probably better to assume that you should be running it on oil.

Old Grease

The problem with older grease products and even some of the newer conceptional grease products like Mobil EP-2 is that the binder of the grease stays behind and the oil and volatiles disappear with use. In theory, as you add new grease, the older spent grease should ooze out as it gets displaced. This is great if you can wipe the crap off but often it oozes out inside a motor or direct drive spindle like on a tenoner's coping heads. After 30 some odd years, this solid goop becomes a nasty 'break down and clean up' job and often creates excess heat as the motor runs. Not a good thing. On a vertical motor application, you often have no choice but to use greasers. Hollow chisel motisers and tenoner coping motors are good examples. In other cases where high speed and super precision are needed, then you are back to varients of oilers. For example, look at the quill assembly on the oliver 287 shaper. That upper bearing alone costs more than most 6 inch jointers in TOTAL!

Additional Topics Needed in this Wiki

Requests have been made in the forums for additional information relating to grease and lubrication. Others with more knowledge are encouraged to update this wiki to help answer these questions.

  • Why certain "modern" lubricants may not be appropriate. Examples would be foaming of detergent oils and damage of copper-based (brass/bronze) gearing.
  • Links to oil viscosity cross-references so that the references to certain oil weights and types in old manuals can be related to modern oils. Also would compare SAE and ISO viscosities and other characteristics.
  • Requests have been made for info on grease to use in specific OWWM, as well as more general applications and information:
  • babbitt bearings on a jointer
  • drill press spindles
  • drill press rack
  • machine ways
  • planer feedworks - needle bearings, chains
  • variable speed pulleys
  • drip rates
  • exchange frequency
  • temperature ranges of effectiveness
  • capacities

Wikipedia has a grease table here

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