Bearings FAQs

What size bearings does NMB manufacture?

NMB is the world's largest manufacturer of miniature and instrument ball bearings. These small bearings range in sizes up to 1 inch outside diameter. Our smallest bearing has an outside diameter of .1181 inch.

Why are NMB's bearings separated in metric and inch series?

NMB bearings follow the worldwide bearing sizing standards. These standards have resulted in two types of bearings, the metric and theinch. A standard bearing refers to a bearing that is in such worldwide demand that large volumes are produced. This virtually guarantees continuity of supply while assuring pricing benefits for your OEM requirements.

What materials are NMB bearings manufactured from?

NMB produces bearings with two types of material. Chrome alloy steel and *DD stainless steel. Stainless steel is recommended for ball bearings in applications where corrosion is a possibility, and is also mainly for miniature bearings in which slight contamination can cause disturbance of operation. Chrome alloy steel is harder, and will provide a quieter run in applications where noise is a major concern. Chrome alloy steel, however, will corrode at a faster rate than stainless steel. (*NMB developed stainless steel material, which falls within the 400 series martinsitic stainless steel grouping)

Do I need different ball bearing types for radial vs. thrust loads?

Yes. If your primary use for the ball bearings is to handle radial loads, you should look for a deep groove radial ball bearing. If you are handling only thrust loads, you will want axial ball bearings. If your ball bearings will need to handle both thrust and radial loads, the angular contact ball bearing is best suited to your needs. Using the wrong type of ball bearings in your application can seriously damage said application, so make sure you are using the right ball bearings for the load bearing you require.

Will stainless steel protect against rust?

Stainless steel is corrosion resistant, but will rust in corrosive environments. Stainless steel will corrode at a much slower rate than chrome alloy steel.

What are shields and seals, and which one is better?

Shields and seals are in place to keep contamination out of the bearing. In order of effectiveness, the enclosures that are offered are as follows: metal shields, rubber non-contact seals, PTFE (Polytetrafluoroethylene) non-contact seals, and rubber contact seals. As the sealing performance is increased, the torque to turn the bearing will also increase. It is important to know the application's condition and life requirements so the best shield or seal choice can be made. Specific information about the description of each seal and the pros and cons can be found in the Shields and Seals section in the catalog, or under Bearing Components in our Bearing Engineering Section.

What is ABEC?

ABEC is the acronym for the Annular Bearing Engineers Committee, the standards committee of the American Bearing Manufacturers Association (ABMA). The ABMA is the organization that set the grades of bearing tolerance accuracy. Higher ABEC level means greater accuracy for bearing dimensions and internal runouts in the manufacturing processes. This dimensional control includes tolerances for outside diameters, inside diameters, width, and various runouts within the bearing. ABEC grade does not control roundness, raceway smoothness, or noise performance.

Does a higher ABEC mean a quieter bearing?

For NMB bearings, a separate noise rating controls noise performance. This rating and its meaning can be found in the Part Numbering Section. Another major factor affecting noise performance is the grease type. For very quiet running, the selection of a quiet grease is very important. Handling, installation and use of preload will also ensure the quietest possible operation.

What is Preload?

Preload is a side load that is applied to a radial ball bearing that takes the extra play between the balls and raceway out of the bearing. The side load is normally applied by a spring, so that the system can expand and contract as the conditions fluctuate. Designing a preload system into a bearing application will ensure the quietest possible operation with the longest life. Please see the Engineering section for recommendations.

How do I hold the bearing in place in my application?

Holding the bearing in place can be done by using adhesive, pressing the inner and/or outer ring in place, or by designing a bearing pocket that will enclose the bearing. Each of these methods has its advantages, as can be seen in the Preloading section. A few rules of thumb apply: For adhesive, care must be taken to keep the adhesive from getting inside the bearing. Adhesive in the bearing will cause the grease to breakdown, and the bearing will fail early. For press fitting the bearing, the shaft and housing tolerances should be kept so that the interference fit does not cause the bearing to bind. There should be some radial play remaining in the bearing after press fit. Also, during the press fit installation process, care must be taken not to damage the raceways and balls by not supporting the rings that are being pressed. For the bearing pocket, care must be taken to keep the inner and outer rings from moving freely in the bearing pocket or on the shaft. Movement can cause heat build-up and premature failure.

What grease is best?

Grease selection will depend on the application conditions. With a wide variety of greases available, solutions are available for most requirements. There is, however, no perfect grease. Each grease has good points, but will fall short in other areas. High temperature greases will not be able to handle very high loads. Quiet greases will break down at high temperature, etc. It is important to know what the application requirements will be so that the best grease can be recommended. Lubrication information and a Table of Commonly Used Lubricants are available for your review.

How fast can a bearing rotate?

The speed of a bearing will depend on the bearing size, the lubrication used, the bearing material, the cage material and how long the life requirement is. Bearings can typically rotate at high speeds with good life performance. The speed rating section contains information on ring rotation. Speed ratings are also listed as part of the index section.

How can I make sure I select the right bearing for my application?

We strongly suggest you contact our bearing application engineers at the time of your design specifications. NMB offers an experienced sales and engineering staff to help in the design and selection process, insuring your success.

Where can I get a bearing catalog?

Contact us directly, and we will send you NMB's miniature and instrument ball bearing engineering catalog.