Babbitt can be characterized as either Tin-based or Lead-based.
Originally Ford Motor Company used tin-based bearing metal (babbitt) made to their own specifications and requirements and produced by the National Lead Company (also producers of Tin and Zinc alloy products).
In typical fashion, Ford paid no apparent regard to what babbitts other manufacturers in industry were using, or how others were naming and specifying it. Ford always suited themselves first.
In subsequent years the automotive industry primarily used the SAE J460 specification and numbering system to describe the composition and requirements of different babbitt grades commonly used in automotive applications.
In the 1980's and 1990's the automotive OEMs also used ISO specification and numbering systems to describe the composition and requirements of different babbitt grades used in automotive components.
UNS numbering systems were also sometimes used to describe the composition and requirements of different babbitt grades.
Today ASTM B23 grade specifications are typically used in a broad range of US industry to describe the composition and requirements of different babbitt materials and grades.
Recently (9/2019) there have been some ill-informed postings on the Model A message boards insisting that Ford never used Babbitt bearings, because Babbitt was at that time a 100 year old 'brand' name, and that Ford produced their own metals. Wrong and wrong.
Actually both lead and tin based white metal bearing alloys were (and are) commonly and commercially known as 'Babbitt', and that is a fact that exists to this day, as seen in the current ASTM specification which covers all grades of both classes.
Lead-based poured babbitt metals were never recommended for use as engine main bearings under impact or cyclical loading, though they were used in some instances in automotive camshaft and transmission bearings (bushings) where the forces acting on the bearing were more uniform and without impact or reversal.
Lead-based poured babbitt won't last long as an automotive crankshaft main or connecting rod bearing. Lead-based babbitt is not discussed further here on Ford Garage.
The following table is a comparison of various specifications of tin-based babbitt bearing grades used for automotive poured and machined bearings such as found on Model A Ford engine crankshaft main and connecting rod bearings.
Chemical compositions of babbitt are expressed in elemental percentages, either as a range, or as a maximum value. Many specifications have been created and obsoleted in the last 75 years, but listed below are the common ones from the last 30 years or so for tin-based babbitt grades.
Sn is tin, Sb is antimony, and Cu is copper. These are the three principle components of tin-based babbitt. All other elements are trace elements in varying maximum allowable levels.
Tin is what actually does all the work of providing the lubricity and the bearing surface.
Antimony is added to the matrix for hardness and to control the shrinkage of the hot poured bearing as it cools.
Copper is added to the matrix to impart both strength and malleability to the bearing to resist fracture.
Lead is only present in trace amounts, less than a half percent.
Other trace elements are allowed but not necessarily desired in automotive engine bearing babbitt.
Pb is lead, As is arsenic, Fe is iron, Bi is bismuth, Cd is cadmium, Zn is zinc, and Al is aluminum.
| Babbitt Specification |
Sn | Sb | Cu | Pb | As | Fe | Bi | Cd | Zn | Al |
|---|---|---|---|---|---|---|---|---|---|---|
| Ford (National Lead Co) | 86.0 | 7.0 | 7.0 | 0.50 | 0.10 | 0.08 | 0.08 | 0.05 | 0.005 | 0.005 |
| ASTM B23 Grade 11 UNS L13870 (SAE J460 Grade 11) |
86.0-89.0 | 6.0-7.5 | 5.0-6.5 | |||||||
| ASTM B23 Grade 3 UNS L13840 |
83.0-85.0 | 7.5-8.5 | 7.5-8.5 | 0.35 | ||||||
| ASTM B23 Grade 2 UNS L13890 |
88.0-90.0 | 7.0-8.0 | 3.0-4.0 | |||||||
| ISO SnSb8Cu4 GM4031M SAE J460 Grade 12 |
0.10 | ~ | ||||||||
| SAE J460 Grade 17 | 85.5-88.5 | 7.5-9.0 | 0.50 | 1.0-1.5 |
In the table above, the various specifications are listed approximately in the order of closest match to the original Ford Babbitt composition produced by the National Lead (and tin) Company.
A variety of nicknames and trade names have been applied to various babbitt compositions over the years such as "High Speed Nickel", "XXXX Nickel", "Government Genuine", "Imperial", "Nickel Genuine", "Diesel Babbitt", and others. It is all branding and marketing! Don't draw any conclusions from the name.
The names may sound descriptive, but actually don't mean very much at all. You really need to know the chemical composition from the smelter that produced it, or the industry specifications that it meets. Incidentally, babbitt metal does not contain any amount of elemental nickel or magnesium, despite whatever marketing name a grade may carry!
Knowing and choosing the right bearing metal is just the beginning. Now you have to find the guy that has the right know-how, the right equipment, and most importantly, the right attitude to pour it at the correct temperatures and according to the bearing metal manufacturer's instructions.
If your rebuilder can't tell you what grade and composition of babbitt he is using, or what temperature he is pouring at, it is time to find another rebuilder! The same is true if you find out he is using lead-based babbitt rather than tin-based babbitt for crankshaft main and connecting rod bearings.
By-guess and by-golly is great for do-it-yourselfers who don't mind doing it over and over again, but a real professional knows the right materials and how to properly use them.