Anatomy of an Insulated Terminal
I took apart an insulated terminal to show why the crimper is referred to as double crimper. If your non-heat shrink insulated crimps do not have three parts find some that do. AMP calls these terminals PIDG connectors.
The spade gets one crimp (left side of photo) and the strain relief barrel (middle of the photo) gets a second crimp where I have scuffed the metal. The "colored dot" side of the jaws, of the "double" crimper, are the appropriate size for crimping this strain relief barrel. Using the appropriate crimper such as the "double crimper" pictured above will create both crimps in one single motion.
If I were to disassemble a heat shrink connector all you'd see is the heat shrink and the terminal. You'd only have two pieces, not three, hence the term "single crimp" as it only crimps the crimp barrel because there is no strain relief barrel on a heat shrink terminal.
Unfortunately, there are two separate tools because there are two different types of insulated connectors!
Double Crimps For Insulated Terminals
This picture shows where the two crimps are placed when using standard insulated three-piece crimp terminals. This is an AMP PIDG terminal.
In The Double Crimp Jaws
One other important thing to consider is the orientation of the terminal. The terminal should always be oriented so the the split in the barrel is facing the top jaw of the double crimper. Just as there is a right and left to the dies there is also a top and bottom..
This photo shows a nice even crimp taking place. You can also see the difference between the top and bottom jaw dies that are closest to you and the ones at the far side of the crimping tool too. It is important to note that the wires should stick out the end of the terminal about 1/16" inch before you make the crimp.
A finished insulated crimped terminal made with the "Ancor Double Ratcheting Tool". As with adhesive lined heat shrink connectors you should avoid the use of a "dimple crimper" on an insulated terminal. This crimp tool makes an "okay" crimp but not one that is equal to something that would be allowed in the aeronautical world. That being said it still passes the Mil-Spec tensile strength load requirements...
Here you can see the "double" part of the double crimp. Both the barrel and the strain relief have been crimped thus the term "double crimper".
Double crimping dies are not intended to be used on adhesive lined heat shrink terminals. These dies are not machined as smoothly as the dies on the single ratcheting crimper I used above and could possibly rip the adhesive lined heat shrink.
Checking The Strength
In the sailing & boating community I often find skepticism surrounding crimped terminals so I wanted to do a little experiment to display the strength of a properly executed crimp.
To do this I used the crimp you just saw being made. The wire used is 12ga UL Listed tinned marine grade wire. This photo shows the crimped butt connector holding the entire weight of two of my anchors. The static load here is close to 70 lbs. on that crimped connector.
The Full Picture
This experiment was not done using special effects or trick photography and you can see that the anchors were not just resting on the floor...
This picture sums it all up. A well executed crimp is very strong.
I got bored with the excitement level of just two anchors and decided to up the ante & try it with four anchors. Shown here is a Rocna 33, Spade A-80 (16lbs.), Super Max 35 and a Fortress FX-16 (10 Lbs.).
Yes, you read it correctly, that crimped connector is supporting close to 95lbs.
FOR THE FULL CRIMP TOOL SHOOT OUT VISIT MY FORUM AND SEE THE VIDEOS AT THE LINK BELOW:
Another Test This Time With NO CRIMP
OK I wanted to test the strength of the adhesive lined heat shrink to decipher it's added benefit in overall total joint strength.
To do this I striped the wire as I would normally do then instead of crimping the butt connector I simply applied heat and melted the adhesive lined heat shrink around the wires jacket.
This photo shows the actual connection that I used in the photo below.
The Results !
I was quite impressed by the durability of just the adhesive lined heat shrink tubing.
The heat shrink alone actually held my 10lb Fortress FX-16 anchor just fine. I then tried my 16 lb. Spade A-80 anchor and the connection failed before I could even turn around and get my camera! Still ten pounds is not bad and it should certainly keep any moisture out. Interestingly enough a yellow terminal crimped with the "el-cheapo" crimpers from the first picture held less than ten pounds in my load testing. Based on that the adhesive is stronger than a cheapo pair of crimpers.... Ouch!!
So the failure point is somewhere between 10 and 16 lbs. static load, for just the heat shrink alone.
As you can see in this picture the jacket stretched, got thinner due to elongation, and pulled away from the adhesive. I had stripped that wire just like I would have had I been crimping it. Before the failure there was considerably more wire showing. If you look closely you can see the remaining adhesive beginning to fail on the end that had not yet come apart.