The complete bearing consists of components that can be purchase separately or as a complete bearing. The components include the inner race, the clamp collars (that hold the inner race halves in place), the roller cage with rollers, and the outer race, which all make up the bearing assembly. The seals protect the bearing from dirt and contaminants, the cartridge contains the bearing assembly, and the housing (pedestal or flange) units which support the cartridge and holds cartridge and bearing assembly in the correct position and height.
The Bearing Assembly
The rollers, inner race, and outer race are made from through-hardened 52100 bearing steel. With Craft's standard through hardening practices, this high carbon chrome, low alloy steel provides excellent load bearing strength and wear characteristics, superior surface quality, and an inherent ability to withstand impact load conditions. Strict statistical process control used throughout manufacturing assures tolerance accuracy, fine surface finish, and consistent high quality.
The clamp collars are made from various mild steels - dependent upon bearing size and series. The materials used are chosen for their ability to be hardened yet retain the ductility required for the repetitive stresses involved with dynamic and constantly varying loads, for millions of stress cycles.
Roller Cage Assembly
In the S1 series up to 3 ½ inch group, standard Craft roller cages are made from Zamac 3 material. Zamac is zinc - aluminum alloy with the desired high lubricity and stiffness qualities. The cage joints are of tongue and groove design and spring steel cage clips are supplied to fasten the cage halves together at installation.
Craft roller cages 4 inch bore and over in S1 series, and in all S2 and S3 series bearings, are made from 932 bearing bronze as standard. Cage joining faces are made with a special “Z” cut to create an overlapping design. The cage halves are secured by counter sunk high tensile socket cap screws, and they come with a thread-locking compound built into the screw (Nylok) that ensures retention of the screws for the life of the bearing.
All of Craft's roller cages are designed with cage pockets to encapsulate the rollers to retain lubricant and ensure accurate roller guidance while possessing extremely low wear characteristics. Once the cage halves are mated and secured around the inner race, the units perform as a solid roller cage.
Triple Labyrinth Seals
Craft's aluminum triple labyrinth (ATL) seals are made from 6061-T6 marine grade/aircraft grade aluminum. The seal bore is machined to accept and retain a double row of molded o-ring material. This provides a seal between the shaft and the bore, as well as allows for shaft movement for expansion and contraction during operation without compromising the seal. By design, the seals rotate with the shaft—this prevents shaft wear at the seal/shaft mating seat, ensuring long live and full sealing capability.
Depending on the application, various o-ring materials are available as an application may require, and the seal can be made from other materials such as UHMW, bronze, or stainless steel.
Cartridges and Housings
Craft's cartridges and housings are made of 65-45-12 ductile iron as standard. Ductile iron, which is far superior to the simple cast iron used by others, was selected because it provides the attributes of steel—high load, superior shock and wear resistance, and low and high temperature endurance. Craft's ductile iron components are protected with a powder coating finish as standard. The powder coating provides a more durable and longer lasting finish over the paint used in other bearings. Other coating types are available as an application may demand. Steel is also available for special applications as well as custom designs for a unique machine.
Bearing cartridges are designed to provide a rigid mounting for the bearings and seals which protect the bearing from contaminants. The labyrinths machined into the cartridges accept the seal O.D. labyrinths, and are lubricated with grease to further enhance sealing capability.
Bearing housings are designed for multiple mounting configurations. The pedestal housing is for mounting on a surface parallel to the shaft. The flange housing is for mounting on a surface perpendicular to the shaft. Both are designed for ease of installation and alignment of shaft and equipment. In addition to the standard sizes in stock, special sizes and housings are available to satisfy the customer's special needs.
Cartridge and housing self alignment
A major cause of premature bearing failure is misalignment which can be caused by misalignment at installation, machine movement, temperature changes, and other factors. The inside diameter of the housings are spherically machined to match the spherical outside of the cartridge assembly. When the pieces are mounted as an assembly, the classic ball and socket is formed. This creates a self aligning capability for the complete assembly. This is a true self-aligning capability unlike others which claim to be able to accept or tolerate some internal misalignment. The self-aligning capability of Craft's housed units is 3-4 degrees per side. To properly facilitate the ball and socket design, the machined surfaces are lubricated at assembly with an anti-seize or moly based compound that serve to both lubricate and protect the machined surfaces in operation. Since the complete bearing assembly is within the cartridge, this allows the bearing and seals to properly align with the shaft, thus allowing the bearing to perform optimally. As a result, Craft has addressed two major causes of bearing failure, misalignment, and contamination.
Grade 8, high tensile steel alloy (hardened and tempered) “Allen” head fasteners are used in Craft bearings. S.A.E. threads are standard. Metric is available upon request. Stainless steel fasteners (external) are available. Fastener sizes, strengths, and torque specifications are in the charts provided herein.