Table of Contents

 When working with mil-spec insulated connectors, it is best to use a nesting type dies like the Eclipse 300-058 (shown on lower left). These have a smooth nested style jaws...no points or sharp protrusions to pierce the insulation.

The jaws that are marked Non-insulated in the right hand photo are the jaws of death for insulated connectors for several reasons...The most obvious is that they punch holes in the insulation. This is a very good utility crimper made by Ideal...if you use it. Use the die marked insulated please. 

Please note that jaws or dies in the photo below have a flat oval shape--no points.  Points puncture the insulation and do not spread the crimp pressure over a broad surface. If your crimp pressure is all in one spot you can cut or crush some of the wire strands and weaken the crimp making the connection subject to a greater chance of failure from vibration.

The dies are double on this crimper. It allows both the barrel and the sleeve to be crimped at one time. Another feature of a good ratchet style crimper is that you can, in a very simple operation, re-calibrate it if it is out of Specs. Also the jaws are removable and can be replaced if damaged. There are other types of jaws or dies available for crimping a wide variety of connectors from BNC to Sub D.

TOP Photo From The Left:Insulation Barrel- Wire Sleeve- Connection Point  

This is a 12/10ga.,  1/4" Mil. Spec. Nylon Ring, #MS-25036-157. The insulation is cut away so you can see the barrel and the sleeve. The sleeve is where the wire enters. The barrel is between the sleeve and the terminal's connection area

   
    Jaws.                                                                 
The barrel crimps on to bare wire strands and the sleeve crimps on to the insulation.  

( Please note the 12-10 markings...good quality connectors always have their wire gauge stamped on them, plus the manufacturer's name or symbol--if they are proud of what they make!  If it's not stamped--don't buy it because you don't know what it's made of.)

The photo above to the right above shows both surfaces of the jaws that do the two crimps at once. Please note the narrow saddle ( far side from this angle ) is where the barrel that crimps to the stripped wire is placed. The wider saddle ( closest side from this angle ) crimps the insulation sleeve The insulation crimp area has a slightly larger opening than the wire crimp side . It is larger to accommodate the extra thickness of the insulation 

If you use a single die crimper remember to do the two crimps on a Mil. Spec. connector. If you are using a single crimp tool, do the bare wire crimp first. It is the crimp area nearest the tongue or ring...( the end that connects )



This is what your crimped  connectors should look like-- oval shaped and uniform. This was crimped on a double crimp tool like the SC-4140.  In the center photo I've cut the wire at the inlet side. Note the oval shape that the wire and insulation has been formed into.  This is caused by the insulation crimp sleeve being formed around the wire. The photo on the far right is where the tongue of the connector was until I sawed it off so that you could see the solidity of the crimp.

Note: #1: The wire ( copper center) is oval shaped and is almost solid. #2: Note the brass color ( the next layer out from the center) The connector used for this example was a Quik On or Push On...this one is made of brass. I used it so that you could see the various layers that make up a Double Crimp Connector. #3: This layer shows the outer layer- the part that crimps on the insulation...which in the Mil Spec connector also crimps on to the bare wire by gripping the barrel portion that crimps on to the bare wire...strain relief.

How to position Insulated Terminals for the best crimp:

NOTE:  It is best to position your connector seam up, or seam faced toward the upper jaw. It will give you a better crimp. This photo is of the seam. Note this seam is brazed shut and will not pop open during or after the crimping process. Mil- Spec connectors have brazed seams. The photo below shows the seam on a terminal.

NOTE:  It is best to place the connector with the open sleeve ( wire entry point ) on the side of the crimper with the gauge markings and/or gauge color dots when using a double die crimper and any other style of crimper. The open barrel is the entry point for the wire. Match your terminal to the gauge indicator on the crimper ( or match colored dots to color of insulation on the connector). Red is 22/18ga. (sometimes red is a variation of red, like pink, but it is still 22/18ga).  Blue is 16/14ga. and Yellow is 12/10ga.

NOTE:  Place your connector in the crimper  ( this is true for all crimpers ) and apply enough pressure to hold it in place. Insert your wire and squeeze the crimper until it bottoms out. Another advantage to using a racheting crimper is that when you squeeze the handles to the point where they release, you'll  know you've completed the crimping cycle-no guesswork!.
 
Open barrel is placed on the side of the die with the colored marks. The ring is on the side without wire gauge dots or gauge markers. 
Test your crimp(s)...pull on the wire. It's much better that it fails now and not later!

Let me say that again for emphasis...Pull on your wire after you finish crimping it. It's better to have it come out now and not while your in the air or on the water. The last photo is of a ring connector I split open. This is what they are shaped like before they roll them up and braze the seam.  Notice the ridges that run horizontally on the rectangular ar

ea. When you crimp this quality connector those ridges are forced into the wire strands...Strain Relief...It's really helpful in high vibration environments.

NOTE:  Strip just enough insulation from your wire so that the strands are even with the outer end of the barrel after insertion. Warning!  Be very careful not to score the wire when stripping the insulation.  It weakens the strands considerably.

Strength:

Test your crimps with a pull test:

(Source: AMP PIDG Application Specification 114-2157)