First I went to the various web sites for the companies that sell rod ends and read their technical data, FAQs and articles that have been written about their products. Then I reviewed the offerings in their catalogs; noting the recommendations included with the item. Once I was familiar with what possible items would serve my purpose, I called their tech help / order assistance line and asked for their recommendations. Here is some of what I learned.
Spherical Rod Ends: Most rod ends are manufactured utilizing one of two construction styles. They are of the two or three-piece type. Both types feature the advantages of metal-to- metal contact between bearing components (PTFE to metal interface may also be incorporated when specified).
The standard two-piece style consists of a body and precision ground oil impregnated sintered steel ball. This type of construction allows the rod end body to carry a greater radial static load and the oil-impregnated ball is self-lubricating under normal operating conditions. This unit also offers greater misalignment capabilities. A variety of material and plating options for the component parts in this series are available. Any cold- formable steel in stainless and alloy steel categories can be specified for the body, and all harden able alloys such as 52100 and 440 C stainless steel may be employed as options for the ball component.
The three-piece style consists of a body, ball, and race. This type of unit, offering fully swaged bearing construction, features the advantages of maximum spherical conformity between the ball and race. It also offers flexibility in that many different types of materials can be interchanged in each component part, providing combinations that can be tailored to meet just about any application requirement.
Lubrication: Grease Grease is oil that has synthetic filler, thickener, metallic soap, or a combination of the three added to prevent oil migration from the lubrication site. The operative properties of grease depend mostly on the base oil. Metal on metal spherical bearings are supplied with lubrication grooves and holes to provide the ability for lubrication. Metal on metal rod ends can be furnished with grease fittings along with the lubrication grooves and holes to allow for lubrication. These bearings could gall without frequent lubrication and a reversing load to keep the grease from being pushed out. In applications with one direction loading, the grease will tend to be squeezed out of the bearing area. These types of applications should be evaluated for the use of dry film or Teflon.
Teflon Liners PTFE (bonded coated PTFE liner) lined races are available in all three-piece bearing units and all spherical bearings. The steel race has a self-lubricating liner; a PTFE impregnated woven fabric, chemically bonded to the inner diameter of the race.
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