FED-STD-228A
Method 1121.1
18 April 2014
THICKNESS, COTTON TAPE; MICROMETER CALIPER
1. SCOPE
1.1 This method is intended for use in determining the thickness of cotton tapes over the insulation of
insulated wire and cable. It is not considered as accurate as method 1124.
2. SPECIMEN
2.1 The specimen should be a piece of the inspection unit at least 2 feet in length from which any
covering over the tape has been removed.
3. APPARATUS AND REAGENTS
3.1 The apparatus and reagents shall be as follows:
3.1.1 Micrometer caliper graduated to read in mils or 0.0001 inch and having flat surfaces on both anvil
and end of spindle, each approximately 0.25 inch in diameter. The surfaces of anvil and spindle shall be
parallel to within 0.0001 inch.
3.1.2 Wiping cloth.
3.1.3 Alcohol or other suitable solvent.
4. PROCEDURE
4.1 The specimen shall be free from mechanical damage. The micrometer caliper shall be applied
directly over the tape so that the specimen can just be moved between the anvil and the spindle without
distortion of the tape. The diameter over the tape shall be read from the micrometer caliper scale and
value recorded as D2. If possible, the measurements shall be made at places where the tape is not
lapped.
4.2 The tape shall then be removed from the specimen and any saturants or other extraneous materials
removed from the surface of the core (assembly under the tape) by means of the cloth and solvent. The
diameter over the core shall then be determined as described for diameter over the tape and the value
recorded as D2. This measurement shall be made over the laps of any tape or over the tops of any marks
in the insulation.
4.3 Three measurements equally spaced along the specimen shall be made. The diameter over the tape
and over the core shall be determined as nearly as practicable at the same point.
4.4 If more than one layer of tape is present, each layer shall be measured separately.
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