FED-STD-228A
Method 1531.1
18 APRIL 2014
LENGTH OF LAY, WRAP OR SERVING
1. SCOPE
1.1 This method is intended for use in determining the length of lay or wraps servings, that is, the
distance parallel to the axis of the conductor in which a serving or wrap makes one complete spiral.
2. SPECIMEN
2.1 The specimen should be a piece of the inspection unit at least 6 inches in length from which any
covering over the wrap or serving has been removed.
3. APPARATUS AND REAGENTS
3.1 The apparatus and reagents shall be as follows:
3.1.1 Steel scale graduated to 1/32 inch or finer or its decimal equivalent.
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 surface of the specimen shall be cleaned
with the cloth and solvent so as to expose the individual yarns. The binder threads shall be cut or broken
and a portion of the wrap or serving unwound for a distance of about one inch from the end of the
specimen. A reference mark shall be placed on the surface of the core (assembly under the wrap or
serving) to locate the edge of the serving at the point where unwinding stopped. Exactly four complete
spirals of the serving shall be unwound and the distance along the axis of the cable from the reference
mark to the edge of the serving measured to the nearest 1/32 inch and the value recorded as 4L.
5. RESULTS
5.1 Calculation. The length of lay of the wrap or serving at any place shall be calculated as follows:
Length of lay, inches=4L
4
where:
4L=the distance in inches along the axis of the cable covered by four spirals of the wrap or serving
5.5 Unless otherwise specified in the detail specification, two specimens from each inspection unit shall
be tested.
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