NICE® Ball Bearings Engineering Data

NICE® Ball Bearings

For more details and a current listing of parts, please visit:
NICE® Ball Bearings

Table of Contents

• Selection Guide
• Engineering Data
  • Design
  • Capacity and Fatigue Life of Ball Bearings
  • Operating Temperature
  • Limiting Speeds
  • Lubrication
  • Retainers/Cages
  • Axial Load Capacity
  • Misalignment
  • Finish and Accuracy
  • Seals and Shields
  • Radial Internal Clearance
  • Recommended Shaft and Housing Fits

Selection Guide

NICE® Ball Bearings, Inc. produces a full line of ground, semi-ground, and unground bearing assemblies. To choose the exact bearing you need, start with the NICE® line of standard inch-dimension, radial, angular contact and thrust ball bearings. Standard series bearings can be customized to include many features that can satisfy the demands of many special applications. They are available with special bores, modified outer ring shapes, extended inner rings, locking devices, and flanged housings. Standards can be ordered sealed, shielded, or open, and are offered in ground and semi-ground grades to deliver the most cost effective solution for your application.

If you are now designing with only ABEC-1 level or higher bearings, chances are there may be a more economical solution to your application. A NICE® application engineer can help you determine the exact precision your design requires, and show you how to take advantage of the savings, selection and special features available in our standard series. Even when a standard isn't the answer, our engineers can deliver an economical, modified standard design that is "fit for purpose."

Engineering Data

The methods, equations, and technical data presented in this section allow the user to select the correct bearings and estimate their performance for a wide range of applications. These calculations apply to the NICE® selection of ground and semi ground product lines, namely the 1600, 3000, 6900, 7500, and 7600 series. For applications with unusual operating conditions, NICE® can provide engineering assistance and recommend the most suitable bearing design.

Where standard bearings cannot be used, NICE® can meet the application requirements with a special bearing design specifically tailored for optimum performance. Contact your RBC Sales Engineer for special sizes, materials, application requirements, dimensions, and tolerances.

Design

Three basic ball bearing types are illustrated to assist in proper design selection.

	Radial bearings are designed prima-rily to carry loads perpendicular to the axis of the bearing bore. They will also accommodate limited thrust loading or a combination radial and thrust load.
	Thrust bearings carry loads applied parallel to the axis of the bearing bore. They are not designed to ac-commodate radial loads
	Combination radial and thrust bearings are designed for simultaneously applied thrust and radial loads. Combination assemblies will also carry pure thrust loading; however, they are not recommended for straight radial loads unless provisions are made to keep the inner rings and outer rings in proper contact with the balls.

Many sizes and types of the three basic designs illustrated are available for selection from this catalog. However,if you have an unusual application problem,NICE field and factory engineers will be glad to give you the benefit of their specialized training and broad practical experience.

Capacity and Fatigue Life of Ball Bearings

The BASIC DYNAMIC LOAD RATING, C, or "dynamic capacity," for a ball bearing is that calculated, constant radial load at which a group of apparently identical bearings with a stationary outer ring can statistically endure one million revolutions of the inner ring.

The BASIC STATIC LOAD RATING, or "static capacity," is that uniformly distributed load, which produces a maximum theoretical contact stress on the most heavily loaded ball of 609,000 psi. At this contact stress a permanent deformation of ball and raceway occurs. This deformation is approximately 0.01% of the ball diameter in inches.

The RATING LIFE L10, is a statistical measure of the life which 90% of a group of apparently identical ball bearings will achieve or exceed. For a single bearing L10 also refers to the life associated with 90% reliability. Median Life, L50, is the life which 50% of the group of ball bearings will achieve or exceed. Median life is usually not greater than five times the rating life.

The relationship between rating life, load rating and load is:

For radial contact ball bearings calculate P with X = 1.0 and Y=1.0. Then recalculate P with X = 0.56 and Y from the chart below. Use the larger value of P to determine L₁₀ life.

Operating Temperature

Maximum recommended operating temperatures for NICE® ball bearings are a function of the bearing cage, seal, and grease materials used in the final assembly. For the NICE® standard precision product series (600, 3000,7500, 7600, and 6900) the maximum recommended operating temperature is 250°F. Operation at temperatures as high as 300°F can be tolerated if of an intermittent nature. When operating at the extremes of allowable temperatures, grease may purge out between the seal lip and the bearing inner ring. If this is unacceptable for a particular application, other design arrangements might be necessary.

The NICE® line of full complement unground series (400,5000, 500, and 600) can operate at higher temperatures than above, and will be limited only by choice of lubricant. However, NICE® Engineering should be consulted for application verification.

Limiting Speeds

Limiting operating speed is dependent upon the materials used in construction and the internal design and finishing of the bearing. For the NICE® standard selection of ball bearings, the recommended speed limits are as follows:

Lubrication

All NICE® double sealed and double shielded precision ground bearings (1600, 3000, 7500, 7600, and 6900 series) are supplied pre-greased 33% full with Shell Alvania #2 grease.

Shell Alvania #2 is a general purpose lithium soap grease with a useful temperature range of -40 °F to +280 °F. Single closure and open bearings are supplied slushed with a rust preservative. NICE® can supply bearings with a wide variety of greases by special order, some of which are listed below. Contact NICE® Engineering for details.

Retainers/Cages

NICE® precision ground ball bearings of standard production are fitted with snap-in ball riding retaining cages made from heat stabilized polyamide 6/6. For special applications or design requirements cages made of special materials can be supplied. These include pressed steel or stainless steel, glass reinforced polyamide 6/6, and brass. Availability of bearings fitted with nonstandard cages should be checked before ordering

Axial Load Capacity

Deep groove ball bearings by nature of their design can carry axial loads either alone or in combination with radial loads. Axial load capacity of standard bearings is 0.5 times the Basic Static Load Rating, CO of that bearing. Smaller bearings should not be subject to a load greater than 0.25 times CO. Excessive axial loads can lead to serious reduction of bearing service life.

Misalignment

Radial deep groove ball bearings do have the ability to accommodate a limited amount of angular misalignment. The amount of angular misalignment that can be tolerated before adversely effecting bearing performance is a function of a variety of parameters. Internal radial clearance, internal design, applied loads, and the size of the bearing all play a role in determining the bearing's misalignment capability. Because of this, exact values for allowable misalignment are not provided. Under normal operating conditions, a safe estimate of permissible angular misalignment is usually between .0005 in/in and .003 in/in. Noise levels may increase when the bearing is operating misaligned.

Finish and Accuracy

NICE® ball bearings are available in several different finish and accuracy grades that may be selected to suit the functionality of a particular application.

NICE® fully ground precision bearings are available in single row radial configurations. Boundary dimensions and internal fit-up are held to exacting tolerances by precision grinding of all external surfaces and both ball grooves. These bearings are recommended for applications requiring quiet running, higher speeds, and applied loads. Normal tolerances for series 1600, 7500, and 7600 bearings range from 0.0005" to 0.001". See product tables for exact tolerances.

NICE® functional precision and unground bearings are designed for those applications where speeds and loads are moderate, and running accuracy and noise requirements do not warrant a fully ground precision bearing. Single row radial, single row angular contact, and thrust ball bearings can be supplied in semi- ground or unground accuracy. Series 3000, 6900, 400, 5000, 500, and 600 bearings are available with functional tolerances that range from 0.005" to 0.010". See product tables for exact tolerances.

Seals and Shields

Contact seals are used on bearings to prevent solid contaminants and moisture from entering the bearing while retaining the lubricant in the bearing. NICE® design and field experience has resulted in a variety of heavy duty and effective sealing designs.

The NICE® RS1P seal, which is standard on the 1600, 3000, and 6900 series bearings, is made of oil and wear resistant synthetic rubber with a steel reinforcement. The sealing action is accomplished via interference (deflection) of the seal lip against a recess in the inner ring shoulder. The outside diameter of the seal is retained in a recess groove cut into the outer ring. The DC seal is an old style multi-part assembly consisting of a nylon seal insert held in place with a metal shield. It is a cost effective seal used only on a few sizes and specials. The NICE® DL and Super Ag seals are special high efficiency contact seals for heavy duty applications. They are constructed of synthetic rubber molded to the back of a metal shroud or guard. The seal lip rides in a labyrinth groove for reduced seal drag and lower torque against the inner ring land surface.

Bearings fitted with non-contacting metal shields are primarily intended for applications where the inner ring rotates and low drag torque is a requirement. They retain the grease at normal operating speeds and temperatures while protecting the bearing from contamination. Metal shields are also utilized in applications where contaminants may pose a threat to the seal materials.

Radial Internal Clearance

All NICE® single row deep groove ball bearings are designed and produced with radial internal clearance to provide for optimum performance. NICE® ball bearings are supplied with "normal" radial clearance as standard, but can be ordered with radial clearance tighter than normal or looser than normal as a special item. The values listed in the table below apply to bearings before mounting and under no load and are supplied as a design guide. Consult NICE® Engineering when ordering other than normal radial clearance.

Recommended Shaft and Housing Fits

Proper mounting fits of ball bearings to shafts and in housings are critical to their performance. Excessively tight or excessively loose fits can result in premature bearing failures. Recommended fit values have been established which will facilitate optimum bearing performance.

The shaft and housing fits listed below apply to the NICE® 1600 and 7500 series bearings. They may also be used for the housing fits only on the 3000, 7600, and 6900 series bearings.