Needle Bearings
Needle
bearing rollers have high length-to diameter ratios. They are quite commonly
used in farm and construction equipment gasoline engines, gear pumps and
small appliances. They may be lubricated with grease but oil based
lubricants are considered for longitivity and smoothness.
Needle bearings have smaller rollers and have the highest load capacity for
a given radial space of all rolling bearings
Loose - needle bearings are full complement of needles in
the annular space between two hardened machine components, which form the
bearing raceways. They have no retainer. Needle bearings provide a bearing
assembly with moderate speed capability, sensitive to misalignment.
Caged assemblies are roller arrangement with a retainer,
placed between two hardened machine elements that act as raceways. Their
speed capability is higher than loose - needle bearings, but the smaller
complement of needles reduces load capacity for the caged assemblies.
Drawn-cup, full-complement needle bearings consist of a
deep-drawn cup with a full complement of needles. In some needle bearings
the needles are retained by the cup lips, in others by the grease.
Spherical-ended rollers are used in the grease-retained needle bearings.
Drawn-cup, caged needle bearings are identical to
full-complement bearings, except that a cage is used. They provide higher
speeds and reduced load bearing capacity. They have better tolerance for
misalignment.
Heavy-duty needle bearings have a heavy outer ring made
from materials, load capacity is higher. There is a problem of slippage
between the roller and raceway surfaces, which occurs because the rollers
are cylindrical rather than tapered.
