Re: Best wire crimper

On 2009-03-30, Michael Koblic <mkoblic@xxxxxxxxxxxx> wrote:
Wild_Bill wrote:

< snip>

I've often used the crimpers intended for bare connectors to crimp
insulated connectors, and they aren't prone to failure if a couple of
things are realized.
The wire used in the connector isn't too small.
The insulated connector is used in the crimping tool space where the
diameter of the insulating material fits the ground notch of the
crimping position.
Enough force is used to fully crimp the metallic sleeve portion of the
connector.
Pull to test the integrity of the connection, and push to make sure
the connection is tight.

This is where I am still somewhat confused: The crimpers I have laid my
hands on so far (not many) have different profiles for insulated and
non-insulated crimping but the insulated profiles are *different from one
another*. For instance mine has a sort of little anvil with a much smaller
nipple opposite for non-insulated but for insulated it is a simple diamond
shaped apperture (slighly rhomboid to be precise - not sure if by design or
by slack tolerance in manufacturing).

O.K. The AMP crimpers for P.I.D.G. (Pre Insulated Diamond Grip)
terminals have two crimping areas. That for the electrical connection
is like this "()" (except that one side of the die is closed on one
half, and the other closed along the other half, so the dies open look
like this (view with a fixed pitch font like Courier to avoid
distortion and confusion):
_ _______
|__ |__
(__ )__
_______| |_

so the wire part is crimped between the parens, and the sides keep the
insulation from squishing out the sides.

And -- the insulation grip part is crimped with a section more like this
(different scale to allow drawing it with ASCII graphics -- again use a
fixed pitch font)
_________
|___ |__
/ \
\___ /___
_______| |_

which produces a diamond-shaped crimp on the insulation grip only.

There are pins holding the halves of the dies with three sets of
mis-aligned holes -- your choice of a hole selects which size of
insulation the grip will hold properly. Set it too tight, and it
squishes out the larger diameter insulations. Set it too loose and it
does not firmly grip the insulation

And of course -- this is only barrel style terminals. There are
also (uninsulated) "flag" style terminals, in which the flags are bent
into 'U's and the ends of the flags dig into the stranded wire. The
crimp looks somewhat like this:
_
/ )
\_)

with the left hand side actually being a continuous curve, but I don't
have oversized parens in the ASCII character set. :-)

These flag type crimp terminals are most often used in pins
which crimp to the wire and then insert into the connector shell.
Perhaps the most common ones are the pins for the DB-25 serial port
connectors for RS-232, but there are larger ones for other different
connectors, including the Molex ones, and AMPs own design of similar
molded connectors. The crimpers from AMP for these various sizes will
all say "Type F" rather than "P.I.D.G." or something similar.

The better ones have two sets of flags -- one for the wire
connection and another for insulation strain relief -- and the
insulation strain relief usually closes to close to a circle instead of
the "flag ends in" pattern used for the connection part.

Note that *all* of the above are for *stranded* wire. Solid
wire needs a different crimp style to make a reliable connection. And I
normally don't use solid wire in combination with crimp terminals.

I tried the insulated portion on a
couple of blue terminals. I mangled the first one. The second one I squeezed
with a bit more circumspection and it came out quite nicely (pull test=OK
:-)

*That* is where the ratchet controlled crimpers win. You *can't*
either mangle the right size terminal or crimp it too lightly. (Well,
you *can* mangle it if you don't set it deep enough into the crimper so
the connection crimp part misses the connection barrel. :-)

The other crimper that I did not buy simply had the same arrangement for
insulated and non-insulated - anvil and nipple - but the insulated was
larger

And this is not the best style for insulated crimp terminals.

Be aware that the insulating material has been compromised, so don't
use it against a conductive part that's at a different voltage
potential other than the particular connection.

I thought as much and with the crimper bought a supply of heat-shrink tubing
:-)

BTW When you are using crimp terminals, you want the insulation
stripped just the right length. With the insulation fully
bottomed in the terminal, there should be just the very end of
the wire extending out the flag or ring end of the terminal. If
it is back inside the crimped terminal a bit, it is not properly
crimped.

I still solder some stranded leads when crimp connectors aren't being
used.

Yes -- there are places were crimp terminals can't be used, and
solder is the right way to go.

In some situations, soldering just the tips of the strands
together for stranded wire, ensures that there won't be any stray
strands.

And when stripping the insulation, a trick to avoid the ends of
the wires fraying out is to just start the insulation off the wire, then
note which direction the wire twists (yes, each batch is likely to be
different from the previous batch), and twist the insulation in that
direction as you pull it off. This causes the strands to lay tight, which
is an assistance when putting the wire into a crimp terminal (having a
strand point back beside the insulation is the same as crimping an
undersized wire), as well as the ability to solder the tip together to
prevent fraying under a terminal screw.

If the solder isn't allowed to wick along the rest of the
strands the wire end will remain flexible enough to withstand being
moved, without causing a fatigue spot at the connection.

Or -- if you use anti-wicking tweezers you can keep just enough
length unsoldered, and have the rest tinned, where you can then form the
tinned section into a hook, hook it through a terminal eye (e.g. on a
tube socket) squeeze it with needle noses for a good firm grip, and then
flow solder once you have all the wires on that terminal.

The Western Union splice is the nearly perfect example of what an
electrical connection should be like.
The contact surface area is greater than the cross sectional area of
the wire.
The electrical connection is mechanically secure.

For solid wire, not for stranded, IIRC.

One T&B tool I have is the multi-purpose tool for stripping, cutting,
crimping for bare and insulated connectors and machine screw cutting.
The crimp point for bare connectors isn't very good, but adequate for
a secure connection.
The notches for stripping are ground sharp to cut the insulation, so
releasing my hand pressure after cutting thru the insulation doesn't
cut into the wire, and makes pulling the insulation almost effortless.
For most small gage crimping purposes, the long handled, forged steel
T&B crimpers perform flawlessly, and have only needed a couple of
drops of oil occasionally.

Note that this design is intended to be a field repair tool, not
a production assembly tool.

In my youth I found one's teeth were the best for stripping insulation. Now
I have one of those tools that does it almost by itself: Grips, cuts and
strips in one squeeze.

And aside from the ones which have the notched blades for each
size of wire, for smaller wire this a similar one called the "Nickless",
which has semi-soft plastic jaws which form around the wire and strip
without nicking the wire. (Nicks are likely to make the wire more
likely to break with vibration.)

In the old days the ability to solder was almost a test of manhood. One of
the knocks against soldering (corrosion caused by the residual flux) was
generally obviated by using violinists' rosin. Even with soldering times
have moved on. When I saw the first temperature-controlled iron I nearly
fainted.

Those temperature-controlled irons are particularly nice when
dealing with soldering transistors or IC (to avoid over-heating), or
when soldering to printed circuit traces, because too much heat will
float the traces free of the board -- especially with the older (and
cheaper) phenolic boards. G-10 glass epoxy is a lot better with heat,
of course.

What about a solder pot for tinning a bunch of just-stripped
wire ends at once?

Enjoy,
DoN.

--
Email: <dnichols@xxxxxxxxxxx> | Voice (all times): (703) 938-4564
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