**Special
calibration notes:** If
you have gone through all the steps in manufacturer #1's example, then this
calibration information will be easier to understand. *(Send us your bolts and
we can measure your bolt coefficients for you. Ask us for an estimate.)*

**Do you have to measure this
"tension coefficient" for every bolt?** No. Just for
every different **type** of bolt and different grip length. You can
use different washers, nuts, flanges, lubricants, and joints, using the
same bolt coefficient.

**How did SureBolt help them measure this
coefficient (Lbs/usec)?** The following explanation will be clearer once you have
finished example #1. So finish manufacturer #1's example and then come back to
this explanation.

Every time you press the RECORD button in SureBolt, the SPARE
parameter and the change in ultrasonic length are also recorded.

So manufacturer #1 used a load-cell (any method to measure
tension) in their laboratory to
measure the actual tension. Then they used SureBolt to measure the change in
ultrasonic length. While SureBolt was measuring the change in ultrasonic length,
they typed the load-cell tension into SureBolt's SPARE parameter (see top middle
of the Record Tension screen).

Then, they used SureBolt's playback screen to graph the SPARE
(lbs tension) parameter on the Y axis, and the change in ultrasonic length
(usec), on the X axis. SureBolt calculates the slope of the line, which is the
lbs/usec coefficient they needed. Manufacturer #1 and #2
determined this coefficient for one type of bolt. Then they used this
coefficient for all bolts of that type and similar grip lengths.

If this is not clear enough, please call us.

This is similar to the way manufacturer #2 used the SPARE parameter to
experimentally measure the temperature coefficient.