AWG Diameter Minimum of Turns
in mm Bare Wire
Wrapping Specifications for Wire
16 0.051 1.30 4
18 0.0403 1.02 4
20 0.032 0.81 5
22 0.0253 0.64 5
24 0.0201 0.51 6
26 0.0159 0.40 7
28 0.0126 0.32 8
30 0.010 0.25 8
32 0.008 0.20 8
Minimum Strip Force
TABLE 1. Wire selection table demonstrating
that a minimum elongation of 15% is required
for 24 through 32 AWG, while 20% is
necessary for larger wire sizes.
Standard versus Modified Wraps
AWG wire. Actually, it is 201.5 / 100.5 circular mils for
a 2.005 ratio — which is almost exactly a doubling in
In a standard wrap, you wrap the bare
wire around the post with the insulated
portion being wrapped only a fraction of a
revolution. You wrap the insulated portion of
the wire between one and two full revolutions
in the modified wrap. The modified wrap is more
secure and better for smaller size wire such
as #30 AWG (Figures 16 and 17 shows the
difference between a standard wrap and a modified wrap.
Wire Wrap Terminal Shapes
Wire Wrap Wire Insulation
As previously mentioned, there are numerous types of
wire wrap insulation with kynar being the most popular
with hobbyists because of its ease of stripping. The wire’s
insulation is no greater than the thickness of either the
wire itself or any less than 80 percent of this dimension.
The smaller the wire, the more it stretches. (Refer to Table
1.) All three popular wire wrap sizes —- 24, 26, and 30 —
have 30,000 psi tensile strength. Wire wrap wire insulation
bonding strength is crucial for automatic wrapping
machinery that has to know how hard to pull to
adequately strip away the insulation. The hobbyist is not
too concerned about this, but kynar insulated #30 AWG
requires three to 12 oz. pull to strip back one inch of wire.
Let’s take a look at for the wire wrap post or terminal.
This piece of hardware is usually square; however, there
are oblong and rectangular shaped posts (see Figure 18).
These are less popular and effective because of the
“pigtail” that typically results. A pigtail is the end of the
wire that does not conform to the shape of the post,
but rather has a tendency to stand out.
There are three rules of thumb with respect to wrap
posts: (1) The wrap post should not be less than one wire
diameter; (2) The wrap post width should not be more
than 2-1/2 times the wrap post’s thickness; and ( 3)
The maximum wrap post width should not be more than
three times the conductor’s diameter. Also, the wrap post
should be long enough to accommodate two wire wrap
connections. A quick rule of thumb for determining the
number of wraps is to divide the AWG number by four.
Therefore, a #30 AWG wire should have approximately
7-1/2 wraps, with the first and last wraps not counting
because they are not involved in the wrap’s bonding.
Some Additional Tips
Examine any wrap post you are replacing for excessive
damage. Critically inspect if the wrap post is starting to crack
and pull away from the board. Insert the wire as far as it will
go up into the bit or wrapping tool. Always dress the wire in
a wrapping direction. Never try to reapply the wrapping tool
FIGURE 19. An unwrapping tool to remove a wrap.
FIGURE 18. Various shapes and types of wrap posts or terminals.