## Enter Your Bolt's Ultrasonic Stretch Coefficient

You would enter the bolt's stretch coefficient where the arrow is pointing. For manufacturer #1's application, the other parameters are not necessary. Press "OK Next Step".

So what is this value?
The manufacturer has already determined this value.

 They experimentally measured a 0.100 usec delay when this type of bolt (at this grip length) had 2856 lbs of tension. Then they calculated this coefficient by dividing 2856 by 0.100 = 28560 Lbs / usec. They used SureBolt's spare parameter to do this.

You may ask "But how do I calculate it?" Good question.
Press here to go to the explanation.

Also, you can let SureBolt calculate this value
if you press the large purple button that says
"Press this button to calculate Lbs/usec using ... "

Press here to see how the screen below changes when you press this button.

Enter the pounds tension required to get your bolt's echo to delay one extra microsecond.

 How do I calculate or measure this coefficient? SureBolt lets you experimentally measure this value for increased accuracy. If you want an explanation on how this was done, press here. Calculate. If you want to have SureBolt calculate this Lbs/usec, enter the 5 parameters as shown below (four red arrows point to four new values that pop-up and one blue arrow points to the Grip Length that now has to have the correct value.) All five values have there own associated errors. Remember, when you multiply or divide, the errors for each operand add. Example: Suppose you know each parameter to +-3%. Then the total error is +-(3+3+3+3+3) = +-15%. All other bolt gages have to use all these sources of error.    Remember this example is meant to get you familiar with taking a tension reading. So now you want to actually record tensions...   See below for each of the screens in this example. You can jump to any screen you want, but we recommend using the Previous Step or Next Step links above.

 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.