It has taken many years of research to find the optimum crimp shape and size for any given combination of wire barrel and wire size. The original form of testing., the tensile or ‘pull-off’ test, still has a role as a production check but the best crimp height for electrical purposes is lower than that which gives the best mechanical strength.
 | As a rule however, it has been found that compressing the wire and terminal of the ‘F’ crimp until the Cross Sectional Area (CSA) is reduced to 85 percent of the original offers the best compromise between electrical integrity and maximum pull-off. See figure M. |
 | To achieve the optimum crimp it is considered advisable to measure the crimp width and height. To control this it is important to have a crimp height micrometer. This is used to measure ‘F’ crimps by laying the scrolled side of the crimp terminal on the micrometer anvil and bringing the spindle down onto the highest point of the underside. On indented terminals the spindle should be lowered onto the bottom of the indent. See figure N. |
Any final CSA that is greater than 95 percent of the original CSA may contain voids or air gaps that could lead to early failure of the crimp joint.
If the CSA is less than 75 percent the tensile strength may be unsatisfactory and a high resistance joint which fails in service may be created. This is because the strands of wire may be damaged by extreme overcrimping.