Q: Why are 52100 steel bearings common,
as opposed to bearings from other steels?

A: 52100 steel has been used in the manufacturing of bearings
for over 75 years.  52100 steel bearings are made from high-carbon
chromium steel, with small quantities of silicon and manganese. 
52100 steel bearings are exceptionally hard and wear resistant,
and are an excellent choice for applications where operating
temperatures are 350°F and below.

52100 steel bearings have a higher dynamic load capacity than
440C stainless steel and are substantially lower in cost than bearings
manufactured from M Series material. 

The composition of 52100 steel bearings is:

Carbon: 0.98 – 1.10%
Chromium: 1.30 – 1.60%
Manganese: 0.25 – 0.45%
Silicon: 0.15 – 0.30%
Sulfur: 0.025% maximum
Phosphorous: 0.025% maximum

52100 steel bearings provide good wear resistance, and are easily
through-hardened to greater than Rockwell C 60.  They can be processed
by conventional manufacturing methods (machining, forging, stamping).

Q. What are the main uses and advantages
of needle bearings?

A. Needle bearings are designed for radial load applications where a low
profile is needed. Needle bearings have long, thin cylinders and are designed
to reduce friction and transmit torque efficiently. High load needle bearings
are used for applications involving static loads, low speeds, or oscillation.
Caged needle bearings deliver as much as three times the speed of
non-caged designs. Needle bearings have substantial lubrication
capacity and are highly resistant to mis-alignment.

Q: What is the meaning of the
ABEC grades for bearings?

A: The ABEC* scale is a qualitative ranking of the tolerances of precision
bearings.  Bearings are rated 1, 3, 5, 7 or 9.  The higher the ABEC number,
the more precise are the tolerances.  Many commercial and even automotive
applications are satisfied using ABEC 1 bearings.  Most aerospace applications,
however, require higher ABEC rated bearings.

Q: What’s the best material
for clutch bearings?

A: Hartford manufactures its clutch bearings from 52100/ GCr15 bearing
grade steel. 52100 is a chromium-containing, high-carbon low alloy material.
It’s through-hardened, and its fatigue properties make it exceptionally
well-suited for bearings used in rotating applications.