Raw material suppliers, manufacturers and end-users of rolling element bearings from the United States, Europe, and Japan are finalizing a new standard specification for silicon nitride-bearing balls. The specification is being developed within Committee ASTM F34 on Rolling Element Bearings.

Jeff Wickwire, quality assurance representative, DCM Buffalo, N.Y., who is leading the development of the proposed specification, said it will benefit silicon nitride material suppliers, ball finishers, and bearing manufacturers or other purchasers of finished silicon nitride balls. “It will be a source of information for those not familiar with silicon nitride,” he said, “and provide confidence that they can order a silicon nitride ball (or silicon nitride material) that will be suitable for their requirements.

“The use of specific manufacturers’ material grade names can be reduced or eliminated. This will foster competition and reduce the problem of changing internal prints and specifications if a particular material grade name changes or goes out of production. Suppliers of materials should only have to meet one specification instead of multiple ones.”

According to Wickwire, the proposed standard specification covers:

• Acceptable material properties for different grades of material—with the grade being dependent on the intended application;
• Acceptable test methods for measuring the properties;
• Some guidance on applications for the different classes of material; and
• Appearance, geometry and finish specifications for finished silicon nitride balls that take into account the unique properties of the material.

Silicon nitride is a relatively new material that has only seen wide usage in the bearing industry within the last 10 years, Wickwire noted. “As a result,” he explained, “many people in the industry do not understand it and this inhibits acceptance. To date, there is no industry specification for either silicon nitride materials or for balls made from this material, and usage is growing rapidly.

“Some ball producers have developed their own proprietary specifications for internal use. This has made it difficult for suppliers of the silicon nitride materials and for end-users of the balls. Suppliers have to meet multiple material standards developed by the ball producers and end-users only have access to finished ball specs originally developed for steel balls. These specs provide no guidance with regards to silicon nitride materials and they are not completely appropriate for specifying finished silicon nitride balls.”

Also within Committee F34, Subcommittee F34.01 on Rolling Elements, which is chaired by Wickwire, is seeking participation for current activities. The subcommittee will develop ASTM specifications for the conversion of Military Standards MIL-B-1089, MS 17130, and MS 17131. Additional end-users are needed to develop steel ball and needle-bearing specifications.

For additional technical information, contact Jeff Wickwire, Quality Assurance Representative, DCM Buffalo, N.Y. (phone: 716/934-2644, ext. 231). Committee F34 on Rolling Element Bearings meets April 30-May 3 at ASTM Headquarters in W. Conshohocken, Pa. For meeting or membership details, contact Staff Manager Tim Brooke, ASTM (phone: 610/832-9729). //

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