Precision
Diameter Tapes
are made from a single piece of stainless alloy. The material
is cut in one piece using non aggressive methods creating two
tape sections. The first is the Gage member, and the second is
the Vernier member.
The curved transition from the Vernier to the Gage member allows
each member of the tape to be matched together without overlapping.
This gives the greatest degree of measuring accuracy.
To accurately use the tape, clean both the object being measured
and the tape. Wrap the tape around the object and align the Vernier
gradients along side of the Gage member gradients. To read a precise
measurement, apply a tension of 5 lbs. (2.25 kg.) to the tape
by pulling the knob on the end of tape. For the most accurate
reading use a calibrated tension scale.
Accurately reading a precision diameter tape is simple and straight
forward. In the illustration above, assume the tape has been stretched
around a pipe that is approximately 42” in diameter, and
the proper 5 lbs. of pull has been put on the tape. Start by reading
the first dimension to the left of the “0” on the Vernier
member. In the example we have 42.125. Next, find the gradients
that line up exactly between the Gage member and the Vernier member.
Read the number on the Vernier scale. In this example the number
is 17. Add this extension to the 42.125 to arrive at the exact
measurement of 42.142.
Metric tapes are graduated in millimeters with each gradient being
.5 mm. On the Vernier scale each gradient represents .01 mm. Readings
are taken the same as the illustration above.
For measuring very large diameter objects, assistance should be
requested, or the measuring tape should be secured by means of
masking tape to assure a parallel measurement.
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