Oilite
Oilite is a trademarked brand of self-lubricating bearings produced through powder metallurgy, consisting of porous sintered metal alloys—primarily bronze or iron-based—that are impregnated with oil to provide continuous lubrication without external maintenance.[1] These bearings are designed for low- to medium-speed applications requiring durability, low friction, and resistance to wear and corrosion.[2] The development of Oilite bearings traces back to 1927, when engineers at Chrysler Corporation, including Carl Breer, William Sherwood, and Bill Caulkins, invented them to address clutch slippage issues in the Chrysler B-70 automobile introduced in 1924.[3] Initially produced by Chrysler's Amplex Division starting around 1930, the bearings gained widespread use in automotive components such as distributors, generators, starters, and water pumps during the 1930s and World War II era.[4] By the mid-20th century, Oilite had expanded beyond automotive applications to include aviation, such as in the Supermarine Spitfire fighter aircraft, and various industrial machinery.[3] Today, the Oilite trademark is owned and manufactured by Beemer Precision, Inc., in the United States (as of 2025).[5] Oilite bearings are manufactured using a powder metallurgy process, where fine metal powders are blended, compacted under high pressure into the desired shape, and then sintered at elevated temperatures to form a porous structure with interconnected voids comprising at least 19% of the volume.[1] This porosity is subsequently filled with lubricant oil under vacuum impregnation, enabling the bearing to release oil gradually during operation for self-lubrication.[3] The standard Oilite bronze composition includes 87.2–90.5% copper, 9.5–10.5% tin, and up to 0.3% graphite, achieving a density of 6.4–6.8 g/cm³, while iron-based variants like Super Oilite use 19–23% copper balanced with iron and carbon for higher load capacities.[1] Key variants of Oilite include the original bronze Oilite for general-purpose use, Super Oilite for demanding conditions with enhanced strength, Oilite Plus with reduced friction properties, and Excelite TX featuring a PTFE coating to eliminate break-in periods.[1] These bearings are applied in diverse sectors, such as electric motors, escalators and elevators, agricultural and construction equipment, medical devices, printing presses, aviation cargo systems, and Formula One racing components, valued for their maintenance-free operation and longevity in oscillatory or linear motion scenarios.[3][2]Overview
Definition and Principles
Oilite is a trademarked brand of porous, sintered metal bearings engineered for self-lubrication, primarily used as sleeve or flange components in mechanical assemblies. These bearings feature a network of interconnected microscopic pores that are impregnated with oil, enabling continuous lubrication without the need for external additives during operation. Developed as a maintenance-free solution, Oilite bearings rely on the inherent properties of their structure to sustain performance over extended periods.[1][6] The core operating principle of Oilite bearings centers on capillary action, where the oil retained in the pores is drawn to the bearing-shaft interface under the influence of frictional heat and load-induced pressure. This mechanism ensures a gradual release of lubricant, creating a thin hydrodynamic oil film that separates the surfaces and reduces friction coefficients. The porosity, typically consisting of 18-22% void space by volume filled with a refined mineral oil, plays a critical role in this process by acting as a reservoir that replenishes the lubricant as it is depleted.[1][7] Under load, the bearing functions by forming this oil film, which supports the shaft and prevents direct metal-to-metal contact, thereby minimizing wear and extending service life. The capillary forces within the pores facilitate oil migration to high-friction zones, maintaining a stable lubrication layer even at varying speeds and temperatures, while the minimal external lubrication required enhances reliability in enclosed or hard-to-access applications. This self-sustaining lubrication principle, invented in the 1920s, distinguishes Oilite from traditional bearings that depend on periodic greasing.[1][8]Historical Development
Oilite bearings were invented in the late 1920s by engineers at the Chrysler Corporation, including Carl Breer, Charles Frederic Sherwood, and Bill Caulkins, as a solution to lubrication challenges in automotive clutches, where traditional oils and greases caused slippage.[9] The development stemmed from observations during testing of Chrysler's B-70 model in 1927, leading to the creation of a sintered metal bearing that incorporated oil within its structure for self-lubrication via interconnected pores.[3] Sherwood's innovative approach built on earlier powdered metal experiments by competitors like General Motors, resulting in stronger, more reliable components.[10] The first patents for Oilite bearings were filed in 1929 and 1930 by Sherwood through his own patent-holding company, securing the technology for Chrysler.[9] In 1930, Chrysler established the Amplex Manufacturing Division to produce these bearings, marking the commercial inception of Oilite as a trademarked product.[9] Official introduction occurred in 1932, with widespread adoption in automotive applications such as distributors, generators, starters, water pumps, and clutch pilots, revolutionizing engine design by enabling maintenance-free operation.[10] During World War II, Oilite bearings gained prominence in aviation, notably featuring in the British Supermarine Spitfire fighter aircraft for critical components requiring reliable, low-maintenance lubrication under extreme conditions.[3] Post-war, production expanded significantly through Amplex, which by 1935 operated a large Detroit plant and grew to become the largest U.S. manufacturer of powdered metal parts, diversifying into industrial sectors beyond automotive use.[9] The division added facilities in Trenton, Michigan (1961), and Van Wert, Ohio (1965), achieving record sales and over 6,000 product variants by the mid-1960s.[9] In 1988, Chrysler sold Amplex to ICM Industries, leading to further acquisitions by Sinter Metals in 1996 and GKN plc in 1997, before the Oilite brand transferred to Beemer Precision, Inc.[10][5] Despite advancements in alternative materials, Oilite remains relevant in the 21st century for applications demanding durable self-lubrication, underscoring its enduring engineering legacy.[3]Materials and Manufacturing
Composition
Oilite bearings are primarily composed of a sintered bronze alloy, consisting of 87.5-90.5% copper and 9.5-10.5% tin, which forms a durable porous matrix suitable for self-lubrication.[11] This alloy also includes up to 1.0% iron and trace amounts of carbon (≤1.75%), with other elements totaling ≤0.5%.[11] Minor additives, such as 0-0.3% graphite, are incorporated to enhance wear resistance within the base composition.[1] The structure features engineered porosity, with interconnected voids comprising at least 18% of the volume, designed to retain oil for prolonged lubrication.[11] These bearings are impregnated with SAE 30 mineral oil, a highly refined turbine-grade lubricant with a high viscosity index, antioxidants, and corrosion inhibitors, ensuring compatibility with the metal matrix and providing initial lubrication content of at least 18% by volume.[12][1] The copper-tin alloy imparts inherent corrosion resistance, protecting the bearing from environmental degradation in typical operating conditions.[1] Standard Oilite formulations support an operating temperature range of -35°F to 300°F (-37°C to 149°C), beyond which the impregnated oil may begin to degrade.[13]Production Process
The production process for Oilite bearings utilizes powder metallurgy to create porous, self-lubricating components. It begins with the preparation of fine metal powders, primarily a bronze alloy of copper and tin, which are blended to ensure uniform particle size and distribution for controlled porosity in the final structure.[1][14] The blended powder is then loaded into precision dies and compacted under high pressure, typically ranging from 25 to 50 tons per square inch, to form fragile "green" compacts that approximate the final bearing shape.[15][16] These green compacts are subsequently sintered in a controlled-atmosphere furnace, heated to 1450-1550°F (788-843°C) in a reducing environment, which bonds the metal particles at their contact points without full melting, resulting in a strong matrix with interconnected pores comprising approximately 19-25% of the volume.[17][1][11] Following sintering, the porous bearings undergo vacuum impregnation, where oil is drawn into the structure under reduced pressure to achieve full saturation of the pores, providing inherent lubrication.[1][18] Finally, the impregnated parts are machined to precise tolerances, followed by quality inspections to verify porosity uniformity, oil retention, and dimensional accuracy.[1][16]Variants
Standard Oilite
Standard Oilite bearings represent the baseline variant in the Oilite family, consisting of sintered bronze impregnated with mineral oil for self-lubrication.[19] This material is produced through powder metallurgy, blending copper and tin powders that are sintered to form a porous structure, which is then vacuum-impregnated with SAE 30 mineral oil.[11] These bearings are available in a wide range of dimensions, from fractional inches (e.g., 1/8 inch ID) to several inches (up to 5 inches OD and 6 inches length) in both imperial and metric sizes, accommodating various sleeve, flanged, and thrust configurations.[1] Load capacities reach up to 2,000 psi for continuous operation, based on projected bearing area, with static limits extending to 8000 psi under low-speed conditions.[20] Design features include cylindrical or flanged shapes that enhance oil retention through interconnected pores, optimized for moderate speeds up to 1,200 ft/min to ensure consistent lubrication without external supply.[1] The low friction coefficient, ranging from 0.05 to 0.10 when lubricated, contributes to their suitability for applications requiring minimal maintenance, as the impregnated oil migrates to the surface during operation.[21] Standard Oilite complies with key industry specifications for sintered bearings, including SAE 841 for composition and performance, as well as ASTM B438 Grade 1 Type II for material properties and quality control.[22]Oilite Plus
Oilite Plus represents an upgraded formulation of self-lubricating sintered bronze bearings, distinguished by the incorporation of a finely dispersed PTFE (polytetrafluoroethylene) additive within the impregnating oil, which reduces friction by approximately 17% compared to standard Oilite.[1] This enhancement promotes smoother and quieter operation, facilitates easier break-in periods, lowers power consumption, and extends overall bearing life, particularly in scenarios involving mixed-film or boundary lubrication.[1] The variant is engineered for improved load-bearing capabilities, accommodating static pressures up to 8,000 psi and dynamic pressures up to 2,000 psi, which supports its use in applications with pulsating or uneven loads.[1] These improvements stem from the PTFE-enhanced oil formulation, which provides better stability under stress without altering the core sintered bronze composition. Oilite Plus utilizes a synthetic turbine oil impregnated with PTFE particles and oxidation/corrosion inhibitors, enabling reliable performance across a temperature range of -60°F to +300°F (-51°C to +149°C).[23] This oil type offers superior high-temperature resistance and lubrication efficiency, with a viscosity of around 522 SUS at 100°F, making it ideal for environments where standard mineral oils might degrade.[1] From a structural perspective, Oilite Plus maintains the porous bronze matrix of traditional Oilite but features a larger pore structure optimized for enhanced oil channeling and retention, allowing for more effective lubricant release during operation under heavy or oscillatory loads.[1] This refinement contributes to its durability in demanding conditions. Available in standard configurations such as sleeve bearings, flange bearings, thrust washers, bar stock, and plates—often denoted by the "AP-" prefix for custom orders—Oilite Plus commands a premium price point due to its advanced features tailored for industrial applications requiring elevated performance.[23][1]Super Oilite
Super Oilite is a high-performance variant of Oilite bearings, featuring a sintered iron-copper alloy base conforming to SAE 863 specifications, which incorporates 18-22% copper with iron as the balance to achieve superior strength and hardness compared to standard bronze-based Oilite materials.[24][25] This composition enables it to handle static loads exceeding 20,000 psi, making it ideal for extreme high-load, low-speed applications where traditional bearings would fail.[26] The alloy's ferrous base provides enhanced durability under heavy pressures, with a maximum PV factor of 75,000 for process-hardened variants like Super Oilite 16.[27] The bearings are impregnated with a proprietary extreme pressure synthetic lubricant, AM3-SPD™, which offers high viscosity and stability for operation in temperatures ranging from -15°F to +300°F (-26°C to +149°C).[28] This lubricant formulation supports performance in harsh environments by reducing friction and wear under elevated pressures and moderate heat, without the need for external relubrication.[27] Unlike standard oils, the synthetic impregnation maintains self-lubricating properties across a broad thermal range, contributing to longevity in demanding industrial settings. Design adaptations in Super Oilite include process hardening and controlled porosity during sintering, allowing for thicker walls and optimized oil retention in forms such as sleeves, flanges, and thrusts.[27] These features enhance resistance to deformation in high-vibration scenarios, with the interconnected pore structure—typically 20% minimum porosity—ensuring consistent lubricant distribution.[29] Certain configurations also exhibit chemical and corrosion resistance, suitable for exposure to corrosive agents in industrial processes.[30]Excelite TX
Excelite TX is a specialized variant of Oilite bearings designed for high-load, low-speed applications requiring boundary lubrication. It features a full-wall thickness of bearing material with a PTFE coating on the surface to eliminate the need for a break-in period, combined with extreme pressure lubrication including a moly additive for enhanced performance.[31][1] This variant supports temperatures from -10°F to +220°F (-23°C to +104°C) and is available in sleeve configurations, prioritizing durability in demanding conditions without external maintenance.[32]Comparison of Variants
The variants of Oilite bearings—Standard Oilite, Oilite Plus, Super Oilite, and Excelite TX—differ primarily in their performance capabilities, material enhancements, and suitability for specific operating conditions, allowing engineers to select based on application demands.[33][1]| Variant | Max Load (P, psi) | Max Speed (V, fpm) | Max PV (psi-fpm) | Temperature Range (°F) | Porosity (% oil by vol., min) | Relative Cost |
|---|---|---|---|---|---|---|
| Standard Oilite | 2,000 | 1,200 | 50,000 | -40 to 220 | 20 | Baseline |
| Oilite Plus | 2,500 | 1,200 | 75,000 | -40 to 250 | 20 | Moderate increase |
| Super Oilite | 3,500 | 1,200 | 100,000 | -40 to 300 | 20 | Premium |