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Crimp Connections.



Far too many of us are chasing electrical gremlins. I’ll wager that 90% of the hair-pulling going on is due to poor connections. The other 10% is truly a defective component.



Basically there are 2 types of electrical connections:

Physical

Mechanical



Physical: A “Physical” connection is an electrical connection achieved by “bonding” the conductors via welding or soldering. The two (or more) conductors are permanently connected by melting or bonding. The joint cannot go bad unless the point of connection physically fails or is broken.



Mechanical: A “mechanical” connection is an electrical connection achieved by friction, crimping, or contact. The connection relies on the contact (touching) of two conductive mediums to make a circuit. Herein are most of the problems.



(Failure of a “physical” connection is obvious. You have a broken wire or connection point at a device. Most of this text will deal with “mechanical” connections, which brings us to….)



What makes a good “Crimp Terminal Connection”, and how to do it!!



Crimp Connector 101

Crimp connectors are wonderful things. An easy, inexpensive way to make what would be a difficult or expensive connection. We all have the remnants of a $ 1.99 assortment pack floating around the workshop. There are also 199 ways to make a WRONG connection with a crimp terminal or 99 cent tool.



*** “Scotch-Lok” Connectors***

These things should be banned. They are the plastic things you stick one wire through, the other into, and squeeze with a pliers. They were designed so U-Haul could make quick connections for trailer rentals, and have NO PLACE ANYWHERE for making a good, permanent electrical connection. Now that my personal pet-peeve has been aired…..



Crimp/Stripper Tools:

Just about everyone has an “electrical connector multi-tool” in their kit. They will have an assortment of stripper gages, and crimping dies. They usually fall into one of two types:

A. A cutter, and 2 or 3 “elliptical” crimp dies at the tip, with stripping dies after the hinge.

B. Pliers, then stripping dies, a cutter, then 2 or 3 “peg and ½ circle” crimping dies after the hinge.

Look for a tool that has what I call the “peg and ½ circle” crimping dies. It’s usually the “B” type (Craftsman #82563) and has a rounded “peg” on ½ the tool, and a mating ½ circle on the other half.

Stay away from the tools that use the “1/2 ellipse - smash” type dies. They won’t produce reliable crimps and are junk! Look and buy a good tool!






Stripping Wire:

This seems to be an overly-simplistic thing, but too many people do it WRONG!

A. Choose the strip die to match the wire gage

B. Look at your connector – only strip off as much insulation as needed to expose copper to the mating surfaces of the connector.

C. Close the tool around the wire squarely

D. Squeeze (cutting the insulation)

E. Let up a bit on the “squeeze” and pull the insulation off.

A properly stripped wire will have only as much insulation needed removed (bare copper won’t be visible outside the connector), the copper strands will still be compacted, and not have any nicks or strands cut loose!



Crimp Connectors:

A. If a properly stripped wire won’t slide into the hole of a connector, you have the wrong gage connector! DO NOT cut off wire strands to make the wire fit into the connector – get the proper size connector!

B. Don’t try and use an oversize connector for a small size wire – you won’t get a reliable connection.

C. There is an “upside” and an “upside-down” to a crimp connector. Look at the connector or inside the round hole. The round hole is formed by rolling flat metal into a circle, and you will usually see a seam (remember this – see Crimping).

Crimping:

A. Properly strip your wire.

B. Insert the bare conductors into the connector (make sure there are no “strays” hanging out).

C. Orient the connector with the seam “up”.

D. Put the crimp tool on the connector, with the “peg” on the OPPOSITE side of the seam, in the middle of the crimp area.

E. Squeeze firmly.

F. Tug on the connection to verify a good crimp.



This is why I prefer the “peg & ½ circle” crimp. By design, the crimp pushes the “meat” of the connector up into the wire, and “rolls” the seam down into the center. It results in a very firm mechanical connection.

The “1/2 ellipse” crimp dies just smash the connector down on the wire, not “rolling” the connector’s metal around the wire. The “ellipse”style crimp allows the wire to slide to the sides and not get mechanically crushed to the connector body.



(Most “factory” crimp connections are made with a specialized tool/die that form a “B” shaped crimp, with a secondary crimp on the insulation (stress relief) of the wire. This is done with and automated machine, and the connectors are on a strip or “gun belt” feeding the machine. These connectors and corresponding crimping tools are available on a “one’sy – two’sy” basis through specialized outlets, but are expensive! A hand tool with dies to crimp 18ga. and 20ga. wire is about $95.00, and you’ll have to buy about 200 connectors.)
 

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We use crimpers at work that are something like $300 each. They work without damaging the insulated terminals. They use elliptical type dies. They have a mechanism like Vise Grips that provides enough force to properly crimp the terminal.

I think the crimper you're talking about is the type that puts a dent in the side of the terminal, right? That's the best type of cheap crimper but it's definately not the best type you can get.

Peter
 

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That is some good advice on how to make crimp connections. I have some additions to your method:

I always tin the wires before crimping the connection. This cuts down on corrosion inside the connection. If using flux-core solder, scrape any flux off the tinned lead after it has cooled. You have to be light with the solder or the resulting tinned lead will be too big to fit in the connector.

I prefer not to use the "peg" on insulated crimp connectors, as it can punch through the insulation. On insulated connectors I use the basic round crimp that squeezes without puncturing the insulation.

On the important connections I also like to apply solder after crimping. This increases the conductive contact inside the crimp.
 

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In some cases I have found the wires look "black" after stripping. In these cases I always gently scrape the wires until I see mostly bare copper.

I do not use nor recommend the peg style crimper as it provides a very localized pressure that can damage the wire strands. I do always give the elipse style crimper an extra hard squeeze and a pull test because I have had problems with them pulling out.

For permanent connections I like to follow the crimp with a solder job. Cheap insurance.

Steve
 

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If soldering the wires to the crimp a potential drawback is that the solder flows along the strands of the wire by capillary action, the strands are now soldered to each other and will not be flexible. They are likely to break just outside the crimp because of this...something to keep in mind if the wire has to make a turn or something just after the crimp.


I like to follow up the crimp/solder with a piece of shrink tube to keep the weather out. Looks nice, too. Problem is half the time I forget to slide the shrink on first, and only discover it AFTER the crimp is on there. :clonk:
 

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I solder crimps nearly all the time. I like the heat shrink over the crimped end, and have started to do that with most of my terminals.

Sometimes, I have crimp terminals that came with plastic insulators. I'll pull off the insulator, crimp and solder, wipe the flux and them quickly slide the insulator back on while things are still warm.

In addition to the crimp tool described, I also like my Snap On crimper. It's die isn't the male/femal shape, but crimps down the edges of the terminal and leaves the center somewhat round.
 
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