Archive for the ‘Radial Ball Bearing’ Category

Rolling Bearings: Parts and Cage Types

Friday, February 27th, 2015

The main parts of the ball bearing are the races and the balls. There is an outer and an inner race. The outer race goes into a bore, and the inner races carries the shaft. In between these two parts is where the balls are placed to create the bearing’s rolling properties.

Likewise, roller bearings follow suit with this placement. In both roller and ball bearings, the rolling element lies between the outer race and inner race. Then, there is a separator between the inner race and the outer race, in which the rolling element actually sits. On the inside of the inner race is where the shaft sits.

Without these basic parts, there is no ball or roller bearing. The image here, from Encyclopedia Britannica Online, shows us how roller and ball bearings are set up within the races.

There are, however, other bearing parts to consider such as flange, shield, and bore. Here you will find a description of these types of parts explained in detail and with a map of terms, from SKF.com.

One additional part, for example, is the bearing cage, or retainer. All rolling bearings contain a cage. Depending on the number of ball or roller sets, the bearing may contain multiple cages. The purpose of the cage is to:

  • Reduce frictional heat in the bearing by separating rolling elements.
  • Evenly space the rolling elements to optimize load distribution.
  • Help avoid damaging sliding movements by guiding the rolling elements while in the unloaded zone.

Cages are stressed by friction, strain, and inertial forces, and can be degraded by high temperatures and certain chemicals. Thus, the design and material of a cage influence the suitability of a rolling bearing for an application. There are different types of cages for different bearing types and operating conditions. Below are three common types of cages.

Stamped Metal Cages: Typically made of sheet steel, stamped metal cages are lighter weight, and provide ample space inside the bearing to help maximize the effects of the lubricant.

Machined Metal Cages: Machined metal cages, typically made of brass or steel, generally permit higher operating speeds.

Polymer Cages: A third type of cage, the polymer cage, which is a fabric reinforced phenolic resin, has characteristics of both strength and elasticity. These cages are able to operate smoothly under poor lubrication conditions.

A panoramic view of the KTV (Koyo Training Vehicle)

Friday, April 13th, 2012

KTV (Koyo Training Vehicle) Panaramic view

Very impressive vehicle. While it was a wonderful day with all the activity, it felt good when it was over. The turnout was wondferful. Thank you to all that stopped by, and thank you to the Koyo representative and driver!

Until next time!!!

How Bearings Are made

Thursday, January 12th, 2012

BEARINGS, HOW THEY ARE MADE
I saw this video this morning and thought it would a good way to start the new year of 2012.  It was interesting to watch, and very informative.

Hope you enjoy it.

Peer Large Bore Bearings, now available….

Tuesday, November 15th, 2011

On our website, Bearings Incorporated; specifically within the Peer Bearing Category check out the Large Bore Series.  This is new to Peer Bearing, and they are as excited about it as we are .  These prices are in effect until December 31, 2011.  Check them out!! Electric Motor Quality, containing Mobile Polyrex EM Grease; they come in Open (C3), ZZD-C3 and 2RLD-C3.

Also check out our new Facebook connection and LIKE our page at Bearings Incorporated at Facebook!

Bearings Incorporated is hosting the KTV again …

Friday, September 16th, 2011

Koyo will be stopping by with it’s KTV on September 28th from 9:00 am to 1:00 pm, and open to Bearings Incorporated past, present and future customers.

Koyo brochure 2011

Here is the printable brochure, and we hope to see you there!!

Timken Extra-Precision Bearings Part 4 of 4

Wednesday, August 10th, 2011

PRELOADING

Description

Preload is defined as the internal load existing in any device before an external working load is applied. The application of preload to ball bearings is utilized to increase the ball bearing unit’s rigidity; to guarantee intimate contact between the rolling elements and the races at all times, thus insuring complete utilization of the actual running accuracies of the bearings; to elimi­nate the possibility of looseness from all phases of bear­ing operation; and to obtain the added effects on the bearing’s basic geometry such as a change in contact angle, a change in strain pattern or a reduction of the minute inaccuracies caused by surface irregularities.

 

Selection

The selection of the type of bearing and the mount­ing arrangement to be used is a function of the operat­ing conditions and requirements of the assembly. A realistic evaluation of these conditions and require­ments must be made in order to establish the design parameters. Often these parameters are contradictory in practice; therefore, the designer must strive for the optimum design through compromise. Design consider­ations, such as speed range, operating loads, rigidity requirements, accuracy desired, and ambient and oper­ating temperatures, determine which type bearing must be used, which type mounting and lubrication is re­quired and whether or not preload is necessary. These factors also dictatethe magnitude of the preload required and the method of its application.

If the design dictates that preload is required, a proper level must then be chosen. It should be stressed that while preload on bearings increases their rigidity it also reduces their life expectancy and increases their frictional drag. Therefore, the choice of the preload level to be incorporated must be made with care. Too often, however, the basic design parameters are contradictory and a compromise preload must be selected.

The Fafnir Bearing Company offers three standard preload levels for the various bearing types and sizes. These preload levels were established to satisfy most application requirements.

In the determination of limiting operational speeds corresponding to the permissible ball bearing preloads for machine tool spindles, many influencing factors are involved. Among those considered are spindle mass and construction; type of mounting; spindle rigidity; accu­racy requirements; spindle loads; service life; type of service, intermittent or continuous; and method of lubrication.

Because of the complexity of this subject, encom­passing all of the factors is difficult. Over a period of several years, data from actual field applications has been accumulated and compiled.   Extra precision ball bearings of the three basic series are included. In certain applications, such as the high-speed motorized spindles, specially preloaded extra-precision ball bearings are required. These bearings are zero preloaded (desig­nated FS-223). This means that the faces of the inner and outer rings are flush ground under negligible load.

Width Tolerances

The width tolerance for individual inner and outer rings is +.000 to —.005, but to allow for face grinding for various preload levels the total width tolerances for duplex pairs of bearings are as follows:

NOMINAL BORE MILLIMETERS                      WIDTH TOLERANCE

       over                   inclusive                      maximum            minimum

o

80

+.000

-.020

80

180

+000

-.030

 

If additional bearings are involved, the total width tolerance is in proportion to the number of bearings.

 

Timken Extra-Precision Bearings Part 3 of 4

Thursday, August 4th, 2011

SHAFT AND HOUSING DESIGN

Shafts

Shafts  are generally made from steel, hardened and ground all over. During the  design of a spindle or shaft it is highly desirable to plan the design  so that the shafts can be ground all over from one setting as a final opera­tion to assure true balance and running accuracy.  This is a basic requirement  for extreme accuracy or high­speed operation.

Housings

Housings  are generally made of cast iron and usually are seasoned to lessen possible distortions. The bore of the housing should be ground or precision bored and checked  at a number of points throughout its length and diameter to assure that it  is uniformly round and not tapered. It is preferable to mount the bearings in one casting. In this way the two or more housing bores required can be machined during one setting, thereby, helping to assure accurate alignment.

In many applications, a quill-type design is required in order to obtain spindle adjustment. This type of assembly can be advantageous,
in certain applications, in that it allows assembly of the bearings on the shaft and insertion of the bearings and shaft into a housing as a
bench assembly. Quill-type designs are also used when the main frame is made of materials having low hardness such as aluminum.

Where screws are used to fasten parts into the main housing, adequate section should be left under the screw holes to prevent
distortion of the housing bore when the screws are secured and the covers or other parts are pulled tightly into place.

Bearing Spacers

Spacers mounted between units of a pair of bear­ings are preferably made of steel, hardened and ground and should be sturdy in cross-section. The length should be produced by grinding the inner ring spacer and outer ring spacer simultaneously. It is important that faces of the spacers are square and that their parallelism is the best possible. All corners should be rounded to remove sharp edges and burrs.

The inside diameter of the inner ring spacer should clear the shaft, but not be so loose as to make it possible to mount and run them
eccentrically. For short spacers and high operating speed a clearance of less than .001″ over the maximum shaft diameter is generally satisfactory. For long spacers and low speeds this clear­ance may be increased to prevent the shaft from dis­turbing the face parallelism of the spacer.

The outside diameter of the outer ring spacer should be about .001″ less than the minimum bore of the housing. The overall design of the inner ring and outer ring spacers should be made so that a minimum of dead air space is left in the cavity between the bearings.

Housing Seals

A labyrinth combination of slinger and end cover provides a highly effective seal against intrusion of foreign material. This seal
design is recommended for use over a wide range of speeds. For exceptional slow speed applications a combination of slinger and com­mercial contact type seal is usually employed.

Slingers should be completely machined to assure true running. Their diameters should be concentric with the bore. The outside diameter of the slinger is often tapered, to throw off cutting compounds, coolants, etc., from the point at which such liquids may enter the spindle. A drip or runout groove adjacent to the open lip of the end cover is highly desirable and practical.

The axial clearances of the internal faces between slinger and end cover should be about 1/16 of an inch. The first radial clearance opening on any design through which liquid may pass should be made very close, approximately .003/.005″ on a side. The inner radial clearance should be between .0075″ and .015″. These figures are based on successful practice.

In sophisticated oil-air-mist lubrication systems it has been found that exhaust porting must be supplied between the bearings and
labyrinth type seals in order to insure adequate lubrication of the bearings and suffi­cient air flow for cooling.

SHAFT AND HOUSING FITS

Shaft Fits

The main purpose of the shaft fit is to assure proper security of the inner ring to the shaft. Under normal conditions of shaft rotation, a loosely fitted inner ring will creep on the shaft leading to wear and peening. This condition will be further aggravated by increase of load or speed. To prevent creeping or slipping, the inner ring should be mounted firmly in place and held securely against the shaft shoulder. However, it is important that the shaft diameter should not be so great an inter­ference fit as to cause undue radial preloading of the bearing. Such a condition could lead to excessive heat generation and increased power consumption.

As a general rule it is recommended that the shaft size and tolerance for seating extra-precision bearings be the same as the bearing bore.
In the case of pre‑ loaded bearings, the ideal shaft fit is a line-to-line fit since an excessively tight fit expands the bearing inner ring and
increases the bearing preload which can lead to overheating. In the case of extremely high-speed applications, however, a minimum press fit of the inner ring is required to insure that the proper fit will be maintained at operating speed. This press fit must be sufficient to compensate for expansion of inner ring due to centrifugal force. Any creeping or shifting of the inner ring on a high-speed device would tend to destroy the balance of the shaft assembly.

The extent of preload change due to an interference fit on the shaft can best be illustrated by the following example: A duplex pair of 2MM9111WI CR DUL bear­ings, with 35 pounds built-in preload, mounted on a shaft that provides an interference fit of .0004 inches will
have a mounted preload level of approximately 180 pounds. This significant increase in preload will result in elevated operating
temperatures.

Housing Fits

Under normal conditions of rotating shaft, the outer ring is stationary and should be mounted in the housing with a hand push or a light tap fit. Should the housing be the rotating member, the same fundamental considera­tions apply in mounting the outer ring that were used for the inner ring mounted on a rotating shaft.

As a general rule for rotating shaft applications, the minimum housing bore dimension for extra-precision bearings should be established
as the maximum bear­ing outside diameter. The tolerance of the housing bore should be the same as the tolerance for the outer ring.

Numerous designs utilize the fixed and floating principle. The previously mentioned fitting practice should be utilized on the fixed
end only. In order to insure that the opposite end will float, and to corn pen-sate for thermal changes within the device, it is neces­sary to supply a looser housing fit. Generally this fit will be sufficient if the average fit is made .0002″ looser than the average fit of the fixed end. If a heat source is present, such as an integral motor, added looseness in the housing will be required.