How to Calibrate a Thread Gage
Engineers rely on thread plug gages to maintain and control an internal threaded hole within a piece of machinery. These gages are oblong, metal pieces specially formed to operate in three common designs - taperlock, reversible, and trilock - to keep a machine working efficiently. By calibrating your thread gages, you ensure that your threads will remain taut and that the gears within your machine will remain in alignment. To calibrate the thread gages, you must calculate the value of the outside diameter of your gage, as well as the value of the optimal pitch diameter.
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Things You'll Need
- Thread gage
- Magnifying glass
- Micrometer
- Package of three fitted gage wires
Instructions
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1
Clean the thread plug gage completely before beginning the gage calibration. Remove any dirt and grime buried deep within the threads and crevices.
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2
Allow the thread gage to acclimate to a temperature between 68 degrees F to 72 degrees F for at least 24 hours.
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3
Inspect all threads visually for cuts, debris, nicks, and other flaws. Use a magnifying glass if necessary to examine closely.
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4
Slide the knob down the micrometer to set it to the proper force necessary for your gage.
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5
Measure the threads with the micrometer at the left and right ends of the gage, as well as in the midpoint of the gage. Record these readings on paper.
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6
Turn the gage 90 degrees clockwise. Once again, measure the threads with the micrometer at the left and right ends of the gage, as well as in the midpoint of the gage. Record these readings on paper.
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7
Take the mathematical average of these six values in order to calculate the value of the outside diameter.
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8
Place two gage wires, the same size that is best fitted to your gage model, among the threads on one side of the gage, on the left end of the gage above the notch. Place a third gage wire among the thread on the side of the gage, opposite the other two wires.
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9
Using your micrometer, measure the gage over the attached wires at one end of the gage. Turn the gage 90 degrees clockwise, and measure the gage with the micrometer once again. Record these values.
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10
Repeat the measurements listed in Step 10 at the other end of the gage, as well as at the midpoint of the gage.
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11
Determine the constant value associated with the fitted gage wires. This value can be found in the informational packet included in the fitted gage wire package.
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12
Subtract the listed Constant value from each measurement taken in Steps 10 and 11.
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13
Take the mathematical average of these values in order to calculate the value of the pitch diameter.
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References
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