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Wire-Wrap Workmanship Standard (NASA)

Unless otherwise annotated, U.S. Government publications are deemed to be in the public domain for American citizens. Since government websites are famous for moving pages around and/or eliminating them entirely, I went ahead and captured this copy of the wire-wrapping workmanship standards as defined by NASA. In fact, many moons ago when working as an electronics technician at the Westinghouse Oceanic Division in Annapolis, Maryland, I attended a week-long class learning to perform soldering, wire-wrapping, and PCB rework per NASA standards. My work involved a lot of building electronic and mechanical assemblies for DoD and aerospace systems, and U.S. Navy inspectors were on-site to perform inspections on everything I built.

I created this page while researching information for this "Bell Telephone Laboratories Advertisement" that appeared in the October 1953 issue of Radio & Television News magazine.

Original Source Page: Discrete Wiring Solderless Wrapped Electrical Connections - Wire-Wrap

You are advised to seek official documentation for work requiring conformance rather than using information on this page.

NASA Workmanship Standards for Wire-Wrapping*
NASA logo Released:
03.31.2000
Revision:
A
Revision Date:
03.30.2001
Book:
3
Section:
3.01
Pages:
1-4

posts with wire wrappings Wire Wrapping

Solderless wrapped terminations are made by helically wrapping a solid uninsulated wire, around a specially designed termination post, to produce a mechanically and electrically stable connection.

Class A: Class A provides improved vibration characteristics, and is the required wrap style for spaceflight hardware applications. This wrap configuration, requires 1/2 to 1-1/2 turns of insulated wire be in contact with a minimum of three (3) corners of the wrappost, in addition to the uninsulated wraps.

Class B: Class B wraps are prohibited.

single termination multiple terminations

Acceptable

Class A – Single Termination

The termination has the required number of insulated and uninsulated turns of wire, and is clean and free of foreign material.

MIL-STD-1130B [ 4.1 ]

Acceptable

Class A – Multiple Terminations

The terminations are properly spaced, with each having the required number of insulated and uninsulated turns of wire, and are clean and free of foreign material.

MIL-STD-1130B [ 4.1 ]

overlapped turns class B termination with no insulated turns

Acceptable

Overlapped Turns

The insulated conductor overwrap does not exceed one (1) turn, and the termination wrap is tight.

MIL-STD-1130B [ 5.3.2.1 b ]

UNAcceptable

Class B

Class B terminations, characterized by the absence of insulated turns, are prohibited.

Best Workmanship Practice

insufficient insulation wrap overlapping wraps

UNAcceptable

Insufficient Insulation Wrap

The insulated section of the termination must be in contact with a minimum of three (3) corners of the wrappost.

MIL-STD-1130B [ 5.3.2.1 a ]

UNAcceptable

Overlapping Wraps

The overlapping wrap must not exceed one (1) complete turn over the last turn of uninsulated wire in a termination directly below it on the wrappost.

MIL-STD-1130B [ 5.3.2.1 b ]

single wrap with improper position multiple wrap with improper position

UNAcceptable

Improper Position - Single Wrap

The first wrap should be located as low on the post as practical, providing sufficient space for additional terminations later.

MIL-STD-1130B [ 5.3.2.1 b ]

UNAcceptable

Improper Position - Multiple Wraps

Terminations in a multiple wrap configuration must be properly positioned to ensure the wraps are completed within the defined termination area of the wrappost.

MIL-STD-1130B [ 5.3.2.1 b ]

insufficient turns end tail at the end of the last turn of the wire

UNAcceptable

Insufficient Turns

The uninsulated section of the termination shall have the minimum number of complete turns, as specified by MIL-STD-1130B, or as noted on the engineering documentation.

MIL-STD-1130B [ 5.3.2 ]

UNAcceptable

End Tail

An end tail is the end of the last turn of wire that is protruding in a tangential direction from the surface of the wrappost. End tails present a risk of shorting.

MIL-STD-1130b [5.3.2.1.d]

overlapping wraps spiral wrap

UNAcceptable

Overwarp

Overlapping wraps reduce the reliability of the termination and may result in severed wraps.

MIL-STD-1130B [ 5.3.2.1 j ]

UNAcceptable

Spiral Wrap

The space between adjacent wrap turns shall not exceed one-half uninsualted conductor diameter. The sum of all gaps shall not exceed one wire diameter, excluding the first and last turn.

MIL-STD-1130B [ 5.3.2.1 f ]

open wrap improper routing

UNAcceptable

Open Wrap

An open wrap is an indicator of an improper termination process and may reduce the reliability of the termination.

MIL-STD-1130B [ 5.3.2.1 f ]

UNAcceptable

Improper Routing

The wire shall not be routed in any manner that will tend to unwrap the termination, and shall be routed around and between the wrapposts in a manner that prevents shorting to adjacent wrapposts.

MIL-STD-1130B [ 5.3.2.1 g ]

damaged wrappost damaged wrappost

UNAcceptable

Damaged Wrappost

The wrappost shall not exhibit evidence of cracking, flaking plating, bending, excessive twisting, gouging or exposed base metal.

MIL-STD-1130B [ 5.3.2.1 a ]

UNAcceptable

Damaged Wrappost

The wrappost shall not exhibit evidence of cracking, flaking plating, bending, excessive twisting, gouging or exposed base metal after wire wrapping.

Best Workmanship Practices

damaged conductor damaged conductor

UNAcceptable

Damaged Conductor

After removal of the insulation, the conductor shall not exhibit nicks, cuts, exposed base metal, ringing or reduction of cross-sectional area. Burnishing of the wire surface is Acceptable.

MIL-STD-1130B [ 5.3.2]

UNAcceptable

Damaged Conductor

After wrapping, the conductor shall not exhibit nicks, cuts, exposed base metal, ringing or reduction of cross-sectional area. Burnishing of the wire surface is Acceptable.

Best Workmanship Practice

damaged insulation contamination on the wire

UNAcceptable

Damaged Insulation

Cut, crushed, gouged, damaged or nicked insulation may result in reduced electrical isolation and/or short circuits. Slight scuffing or discoloration is Acceptable.

Best Workmanship Practice

UNAcceptable

Contamination

Contamination reduces the reliability of the termination.

Best Workmanship Practice

stranded conductor silver underplating

UNAcceptable

Stranded Conductor

The use of standard conductor for wire wrapping is prohibited.

Best Workmanship Practice

UNAcceptable

Silver Underplating

The use of wrapposts with silver underplating is prohibited. Gold plating over nickel is preferred.

MIL-STD-1130B [5.3.2.1 a]

Disclaimer on NASA Website:

All diagrams and visual aids included in this section are intended to provide insight to certified operators, inspectors and instructors who visually assess the compliance of flight hardware to locally applicable requirements. The statements found in this pictorial reference are not intended to be applied as requirements and this pictorial reference should not be applied to contracts. Your project or contract requirements should take precedence over the pictures and statements in this pictorial reference if there is a conflict. Refer to your local project or contract documents for applicable workmanship requirements.

See NASA Workmanship Standards Program Website.

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