Gravity Rollers are the means by which products are transported in many types of gravity conveyor systems. They are available in sizes from 1" dia. x 16 ga. with a 1/4" round axle, up to an 8" dia. x 1" wall with a 3-7/16" round axle. Hex axle sizes are available from 5/16" through 1-1/16".  Numerous bearing options are available as well as special coatings like urethane and zinc plating.

Power Rollers with Sprockets are the means by which products are transported in many types of heavy duty powered unit handling conveyor systems.  These rollers use type "A" plate sprockets welded to tubes for use in chain driven live roller conveyor.  Single or multiple sprockets per roller are available.  They are available in sizes from 1.9" dia. x .145" wall with a 7/16" hex axle up to a 5" dia. x 3/4" wall with a 1-7/16" round axle.  Hex axle sizes available from 7/16" through 1-1/16".   Numerous bearing options are available.  Location of sprockets, chain size and number of teeth must be specified.  Hardened tooth sprockets are also available.

Lineshaft Rollers are provided with one, two, or three grooves rolled into the tube to accommodate 3/16" diameter urethane belts.  Location of grooves must be specified.   Standard roller diameters include 1-3/8", 1.9" and 2-1/2".   Other sizes are available.

Bearings can be divided into four groups:   Non-precision, semi- precision, precision, and journal bearings. Refer to other sections of the Sanders Equipment LLC website for more details.

Non-Precision Bearings have hardened steel balls and raceways.  They are often referred to as "full compliment" meaning they do not have a ball retainer.  The outer race is either stamped or machined.  Non-precision bearings are used where speeds and loads are moderate.

Semi-Precision Bearings have hardened steel balls and raceways along with a ball retainer or "cage" to separate the balls. These bearings are suitable for speeds up to 400 rpm.

Precision Bearings have hardened and ground balls, raceways and ball retainers.  They are normally shielded and sealed.  Precision bearings are suitable for speeds above 400 rpm and for heavier loads.

Journal Bearings consist of a housing and a bushing.  They have no balls or seals.  The housing is generally plastic or wood.  Journal bearings are used in wash-down or similar conditions.

Bearing Components

Races are the inner and outer surfaces that are in contact with the balls.  Non-precision and semi-precision bearings have a machined inner race and a machined or stamped outer race.   Both races are hardened steel.  Precision bearings have inner and outer races made of higher quality steel which are machined, hardened and ground to a fine finish.

Balls are the medium between the inner and outer race which allows the outer race to rotate while the inner race is held stationary.  Balls in non-precision and semi-precision bearings are hardened steel.  Balls in precision bearings are hardened chrome alloy steel.

The Ball Retainer separates the balls from each other, minimizing noise and contact friction between balls. 

This enables higher operating speeds.

Shields and Seals help keep contaminates out of the bearings.  A shield is generally made of steel.  It "shields" contaminants from falling directly into the balls.  A shield can be used by itself or in conjunction with a seal, in which case, the shield will also protect the seal from damage.  Seals are available in Teflon, felt, rubber, nylon and Mylar. Seals affixed to the outer race also contact the inner race.  They create a slight frictional drag, but seal out contaminants while helping to retain grease within the bearing. Standard seals are suitable for temperatures up to 225° F.

Bearing Lubrication

Oiled bearings are generally used in gravity applications requiring a low coefficient of friction.   The temperature range of standard oil is 0° to 200° F.

Grease Packed bearings are generally used in powered applications.   The temperature range of standard grease is -10° to 225° F. They are suitable for higher humidity applications.

Regreasable bearings share the same features as grease packed bearings and, in addition, are designed to accept more grease through a grease fitting located on the end of the axle.  Regreasable bearings have either a drilled inner race or an extended back closure.

Axle Specification

Axles are typically hexagonal to avoid rotation in the frames and to prevent the inner race in the bearings from rotating on the axle, however, round axles are also available.  Larger sized round axles are kept from rotating by use of a keeper bar. Bearings used on these larger axles usually have set screws or eccentric locking collars to prevent inner races from rotating.

Pin or Ring retained axles have a hole drilled in each end of the axle to accommodate cotter pins or hog rings.  Axles can also be drilled for pressure lubrication of bearings.  Pin retained axles are offered in hex sizes of 1/4" thru 1-1/2" and in round sizes of 5/16" through 3-7/16".

Spring Retained axles have two upsets or "dimples".  When assembled into a roller, the axle is held in place by dimples between bearings.  A spring retained roller is assembled into a frame by first inserting one end of the axle into the frame.  The free end of the axle is then depressed and dropped into the other side frame.  Removing the rollers is equally as simple.  Spring retained axles are available in hex sizes of 5/16" through 11/16" and round axle size of 1/4"

Keeper Bar retained axles have a hole and machined flat on one end.   The keeper bar is welded to the frame and rests against the flat surface of the axle, preventing it from rotating.  The hole is for a cotter pin which holds the axle in the frame.  Keeper bar retained axles are used only on round shafts 1" in diameter and larger.

Roller Construction

Tubes are specified by outside diameter (O.D.) and wall thickness.   Diameters from 1" through 8" are available. 

Wall thickness is expressed in either a gauge or a decimal dimension.

Counter Bored rollers have a tube which has its inside diameter bored to the correct size for the bearing to be press fit into place.

Crimped rollers have a tube which is crimped down over the bearing to hold it into place. 

Bearings installed in this manner are non-replaceable.

Rollers provided with an Adapter use a combination of a bearing and an adapter.  The bearing is first press fit into the adapter and the adapter is then press fit into the tube.

Roller Capacities

Roller capacity refers to the maximum load a single roller can support.   Key factors in establishing a roller's capacity are as follows;

    - Bearing capacity
    - Bearing offset (distance from side frame to centerline of balls)
    - Axle deflection
    - Tube deflection

Most manufacturers base capacities of rollers upon tube deflection of no more that .21% of BF and axle angular deflection of no more that 1" at the bearings.  Angular deflection of axle at the bearings is limited to .75" for cylindrical semi-precision and precision bearings.

Because the conveying surface of products is not perfectly flat, use only 2/3 of the rollers under the product when calculating the required roll capacity.

Common sense tells you that it is not practical to use 1-3/8" diameter roller on 1-1/2" centers for a 6000 lb. product (12" x 120" long), so in addition to the rule above, use the following guide lines: