Note: suggested tip distance 1/4″ to 3/8″ at the bottom of the Spiral Contractometer.
1. Put Helix in the plating bath and when the helix has reached the plating bath temperature, loosen the screw that holds the pulley wheel tight against the top of the center rod and position the dial by rotating it to match the zero with the arrow. Then tighten the screw to secure the rod so slippage cannot occur during the calibration and plating steps.
2. Put the loop of a calibration thread over the pulley calibration wheel that is across from the arrow mark and wrap the string part way around the calibration wheel in a clockwise direction (to get the Kc value) on the bottom pin first..
3. Loop the thread and 0.5 avoirdupois ounce weight over the notched guide wheel near the Kc mark in a manner that the weight hangs free from touching any object.
4. Put the loop of the second calibration thread over the remaining pulley calibration pin and wrap the thread in a clockwise direction part way around the calibration wheel, then loop the thread over the notched guide wheel near the remaining Kc mark.
5. With the weights hanging freely, lightly tap the top of the contractometer pulley assembly to equalize the dial position. Use a blunt instrument for this purpose and not a finger since finger motion tends to pull in a sideways direction. Record (for later use) the degree number across from the arrow point as the compressive stress Kc value.
6. Remove the strings and weights. Verify that the dial position has returned to zero. If not at zero, repeat the above calibration steps. As an option, the helix calibration step can be repeated and the results can be averaged. This additional step is recommended for certification purposes.
7. Repeat Step 2, this time wrapping the thread in a counterclockwise direction (to get the Kt value).
8. Repeat Step 3, looping the thread over the wheel near to the Kt position so the weight hangs free.
9. Repeat step 4, in a counterclockwise direction, looping the thread over the wheel near the remaining Kt position.
10. Repeat step 5 with the weights hanging freely. Record the number of degrees tensile stress as Kt for later use.
11. Repeat step 6.Then remove the calibration strings and weights. Again, confirm that the circular degrees dial has returned to the arrow point mark. Repeat and average the results if certification is required.