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From digest.v6.n554 Sat Apr 19 06:56:08 1997 From:
Date: Sat, 19 Apr 1997 01:13:31 -0400 (EDT) Subject: <BMW> Angle Torque

The following was written by fellow coworker Ed Anastasio. It is presented as written.

Ever lie awake at night wondering about the relationship between "angle of turn" and "torque"??
Not to many of us have!
But this relationship is very important to anyone who assembles parts with nuts and bolts.
After properly seating the parts to be mated, the next critical step is to apply the "right stretch" to the bolts to hold them together. "Stretch" is applied by two methods "torque value" and "angle of turn". We're most familiar with torque values. Torque values assume that the coefficient of friction (big term-means slickness) of the bolts and nuts is always about the same. So by applying the same torque range we always get about the "right stretch".
When the bolts and/or nuts are "slicker" than normal we can get into trouble using only torque. Since they slide easier we can turn them further before the minimum torque value is reached. This ends up in a heck of a lot more stretch than the bolts are designed for and sometimes can yield the bolt (that awful spongy feeling) or even break them. In cases like this "engineers" like to use a combination of torque and "angle of turn" to limit the amount we can turn the bolt or nut, once the mating parts are seated, regardless of how slick the nuts and bolts are. Yep, you're right!! This is where the "angle of turn" comes from. The torque range used with an angle of turn is for reference only to assure us that the angle of turn has applied the "right stretch" and nothing is abnormal. Still with me?? No!! well just remember a few thing about "angle of turn".

  1. Never exceed a maximum angle of turn value. (Stay as close to the average value as possible).
  2. The torques given with angle of turn's are for reference only. When you apply the of turn the resulting torque value must be within the referenced range. If not, something is wrong. Disassemble to determine the problem-do not exceed the angle of turn. Do not apply additional torque after applying the angle of turn.
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