Wire Wrapping Overview
As the electronics industry has advanced in technology, the need for a faster, more
reliable and inexpensive method of making electrical connections has become a
necessity. In years past, it was sufficient to solder most connections since there was
ample room between terminals and relatively few connections by today’s
standards. However, today’s electronic equipment is far more complex, leading to
many more terminals. The task is compounded by the reduction in equipment size.
The end result is far more terminals - in much less space. To solve this problem, the
industry has had to adapt to a completely different type of connection. The
solderless connection by wire wrapping technique is now a standard method of
making connections to terminals in high density electronic equipment.
The Technology of Wire Wrapping
A wire wrapped connection is made by coiling the wire around the sharp corners of a terminal under mechanical tension. This
method of connection was developed by Bell Telephone Laboratories, Western Electric Company.
Metal-To-Metal Contact Types of Wrapping Tools Types of Wrap
● Pneumatic tools are preferred for
2
production work. Regular Modified
● Where compressor air is not available,
electric tools are recommended.
● Battery or hand operated tools are
used for service and repair work.
By bending the wire around the sharp
Easy Removal
● A “Regular” bit wraps the bare wire around
corner of the terminal, the oxide layer ● A distinct advantage of wire wrapping
the terminal. A “Modified” bit wraps a
on both wire and terminal is crushed or is the ease with which a wire may be
portion of insulation around the terminal in
sheared, and a clean, oxide-free metal- removed from a terminal to correct
addition to the bare wire. This greatly
to-metal contact is obtained. errors or modify wiring. An unwrap
increases the ability to withstand vibration.
tool is slipped over the terminal,
engaging the first turn of the
High Pressure Contact connection. Rotating the tool, the
connection is removed in seconds, Strength of Connection
without damage to the terminal.
● The strength of a wire wrapped connection
is considerably in excess of that of a
soldered one. It is less easily stripped from
Wire the terminal and is less subject to breakage.
● Solid wire is used for wire wrapped
connections. Copper is the most
commonly used wire. Minimum Gas Tight Contact Areas
elongation of 15% is required for 24
through 32 AWG; 20% for larger wire. ● The contact areas of a wire wrapped
connection remain gas tight when exposed
Terminals Suitable for Wire to temperature changes, corrosive
Wrapped Connections atmospheres, humidity and vibration.
Quality Assurance
● Our bits are subjected to a series of “Strip” Force Chart*
“Qualification Tests”. These consist of
wrapping groups of wire on various Wire Size Min. number Min. strip
types of test terminals. The wrapped AWG Dia. Dia. of turns force
wires are then subjected to a “Strip” inches mm (Bare Wire) lbs. gms
test to determine adequate tightness. 16 .051 1.30 4 15 6800
“Unwrap” tests are also performed to 18 .0403 1.00 4 15 6800
ensure against an “Overtight” wrap.
20 .032 0.80 5 8 3600
Triple Connection 22 .0253 0.65 5 8 3600
24 .0201 0.50 6 7 3200
26 .0159 0.40 7 6 2700
28 .0126 0.32 7 5 2200
30 .0100 0.25 7 3.3 1500
*Conforms to MIL-STD-1130B
OK Industries Inc. Tel (914) 969-6800 Fax (914) 969-6650 www.okindustries.com
How to Select Wire How to Make Wire Wrapped
Connections with OK Tools
1. Determine Wire Gauge
2. Select Regular wrap (bare wire only
around terminal) or Modified wrap (first Step 1
11/2 turns of insulation around terminal, Bit, Sleeve and
balance of turns - bare wire) Pre-Stripped Wire
3. Determine terminal diagonal using
terminal diagonal chart below
4. Select Bit (and corresponding sleeve) using Step 2
charts on page 8 by using wire gauge, Wire Insertion
regular/modified wrap then terminal hole
diameter
5. Insure the terminal diagonal fits between Step 3
minimum and maximum terminal diagonal
on bit and sleeve chart Wire Anchoring
Wire Size Chart Notes:
A. Once bit is selected, the corresponding
Bare Wire Dia. AWG SWG sleeve part number is printed along side
Inches mm (USA) (GB) B. Bits marked with an asterisk (*) are for use
on .025" (.63mm) square terminals Step 4
.0403 1.022 18 C. Modified wraps are recommended for wire Terminal Insertion
.040 1.016 19 diameters 26, 28, 30 AWG (.40, .32, .25mm)
.036 0.914 19 20 when used on .025" (.63mm) square
terminals Step 5
.032 0.813 20 21 Finished Connection
3
.028 0.711 21 22
.0253 0.643 22
.024 0.61 23 Some Hints on Making Wrapped Connections
.0226 0.574 23
.022 0.559 24
.0201 0.51 24
.020 0.508 25 Open Spiral
Overwrap Wrap Wrap
.018 0.457 26
.0179 0.455 25 Easy Does It! Stay With It!
.0164 0.417 27 Do not press too hard. Let the OK tools Just keep the OK tool on the terminal
.0159 0.404 26 do the work. Excessive pressure can until the wrap is complete. Early
.0148 0.376 28 lead to overwrapping. Backforce "BF" removal can result in spiral and open
to prevent overwrapping is available wraps.
.0142 0.361 27
on most power tools and is recom-
.0136 0.345 29 mended for use with 26 through 30
.0126 0.320 28 AWG wire.
.0124 0.315 30
.0116 0.295 31 Pigtail
.0113 0.287 29
.0108 0.274 32
Insufficient Use the Correct Bit and
Turns
.0100 0.254 30 33 Sleeve!
.0092 0.234 34
Feed Wire Correctly! Wire wrapping is a precision technique
.0089 0.226 31 It’s easy to feed wire into the slot in and the wrong bit and sleeve just
the OK bit correctly. Be sure the cannot do the job. Improper selection
.0084 0.213 35 stripped end of the wire is “pushed-in” can cause problems ranging from
.008 0.203 32 all the way. “Pigtails” to loose wraps.
Terminal Diagonal Chart Dimension “F”
In. .010 .015 .020 .025 .030 .035 .040 .045 .050 .055 .060 .065 .070 .075 .080 .085 .090 .095 .100
mm 0.25 0.38 0.51 0.64 0.76 0.89 1.02 1.14 1.27 1.40 1.52 1.65 1.78 1.91 2.03 2.16 2.29 2.41 2.54
.010 .014 .018 .022 .027 .032 .036 .041 .046 .051 .056 .061 .066 .071 .076 .081 .086 .091 .096 .101
0.25 0.36 0.46 0.56 0.69 0.81 0.91 1.04 1.17 1.30 1.42 1.55 1.68 1.80 1.93 2.06 2.18 2.31 2.44 2.57
.015 .018 .021 .025 .029 .033 .038 .043 .047 .052 .057 .062 .067 .072 .077 .082 .087 .092 .097 .102
0.38 0.46 0.53 0.64 0.74 0.84 0.97 1.09 1.19 1.32 1.45 1.58 1.70 1.83 1.96 2.08 2.21 2.34 2.46 2.59
.020 .022 .025 .028 .032 .036 .040 .045 .049 .053 .058 .063 .068 .073 .078 .083 .088 .093 .098 .103
Dimension “E”
0.51 0.56 0.64 0.71 0.81 0.91 1.02 1.14 1.25 1.35 1.47 1.60 1.73 1.85 1.98 2.11 2.24 2.36 2.49 2.62
.025 .027 .029 .032 .035 .039 .043 .047 .050 .056 .060 .065 .069 .074 .079 .084 .089 .094 .099 .104
0.64 0.69 0.74 0.81 0.89 0.99 1.09 1.19 1.27 1.42 1.52 1.65 1.75 1.88 2.01 2.13 2.26 2.39 2.52 2.64
.030 .032 .033 .036 .039 .042 .046 .050 .054 .058 .062 .067 .071 .076 .080 .085 .090 .095 .100 .105
0.76 0.81 0.84 0.91 0.99 1.07 1.17 1.27 1.37 1.47 1.58 1.70 1.80 1.93 2.03 2.16 2.29 2.41 2.54 2.67
.035 .036 .038 .040 .043 .046 .049 .052 .056 .060 .064 .069 .073 .078 .082 .087 .091 .096 .101 .106
0.89 0.91 0.97 1.02 1.09 1.17 1.25 1.32 1.42 1.52 1.63 1.75 1.85 1.98 2.08 2.21 2.31 2.44 2.57 2.69
.040 .041 .043 .045 .047 .050 .052 .056 .060 .064 .068 .072 .076 .080 .084 .089 .092 .097 .102 .107
1.02 1.04 1.09 1.14 1.19 1.27 1.32 1.42 1.52 1.63 1.73 1.83 1.93 2.03 2.13 2.26 2.34 2.46 2.59 2.72
.045 .046 .047 .049 .050 .054 .056 .060 .063 .067 .071 .074 .078 .083 .087 .091 .096 .101 .105 .109
1.14 1.17 1.19 1.25 1.27 1.37 1.42 1.52 1.60 1.70 1.80 1.88 1.98 2.11 2.21 2.31 2.44 2.57 2.67 2.77
.050 .051 .052 .053 .056 .058 .060 .064 .067 .071 .074 .078 .082 .086 .090 .094 .098 .103 .107 .111
1.27 1.30 1.32 1.35 1.42 1.47 1.52 1.63 1.70 1.80 1.88 1.98 2.08 2.18 2.29 2.39 2.49 2.62 2.72 2.82
Example: If “E”=.020”. “F”=.060”. The terminal diagonal is .063" as shown on chart.
OK Industries Inc. Tel (914) 969-6800 Fax (914) 969-6650 www.okindustries.com
