Discrete Wiring - Solderless Wrapped Electrical Connections: Wire-Wrap

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*
	Released: 03.31.2000	Revision: A	Revision Date: 03.30.2001
	Book: 3	Section: 3.01	Pages: 1-4

	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.

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 ]

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


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 ]

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 ]

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]


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 ]

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 ]

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


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

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

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.