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Back to Back Configuration<br />
The most common<br />
technique used is back to<br />
back, "O", or "DB "<br />
mounting. In this<br />
configuration, the inner<br />
races are relieved. When<br />
the inner races are<br />
clamped together, the<br />
relief clearance is<br />
eliminated, resulting in<br />
the correct pre-load. This<br />
configuration is suited for<br />
most applications and<br />
provides good accuracy<br />
and rigidity.<br />
Tandem Configuration<br />
Figure 7. BACK TO BACK DB-Mounting<br />
Generally, a combination<br />
of mounting techniques is<br />
used in a <strong>spindle</strong><br />
assembly. In many cases,<br />
two or three bearings are<br />
placed near the <strong>spindle</strong><br />
nose, with a pair mounted<br />
near the rear of the<br />
<strong>spindle</strong> shaft. This<br />
mounting is known as<br />
"Tandem" or "DT".<br />
Tandem mounting does<br />
not allow forces in both<br />
directions, unless another<br />
pair of bearings are used<br />
on the <strong>spindle</strong> shaft,<br />
facing in the opposite<br />
direction. To increase<br />
moment loading capacity<br />
and <strong>spindle</strong> performance,<br />
Figure 8. TANDEM DT-Mounting<br />
spacers are used to<br />
separate the bearing sets.<br />
This is generally the case in most motor-<strong>spindle</strong> designs. The <strong>spindle</strong> designer will use two or<br />
three bearings in the front in a tandem setup. At the rear of the <strong>spindle</strong> shaft, another bearing<br />
pair, of equal size or smaller, will be used in a tandem arrangement as well. Together, the bearing<br />
sets form an overall "DB" or Back-to Back setup. The <strong>spindle</strong> shaft and <strong>spindle</strong> housing locate the<br />
bearings.<br />
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