Technical Info

Crimping Technology for Europe and North America

The term crimping means to press, make an impression, fold or deform by folding. In electrical work, crimping is the mechanical compression of a sleeve around a conductor to make a firm mechanical contact between the conductor and the connector. Crimps have to a large extent replaced soldered connections, and have proven extremely suitable over the years in which they have been in use. They are only permitted, however, if they satisfy the applicable DIN, SAE or customer requirements. To do this, the conductor, contact, crimping tool and tool setting must all be coordinated.
This means:

• The conductors and connectors must match in terms of capacity values. The stripping length and positioning of the conductors in the connector should comply with the requirements of the specific connectors.
• Conductors and connectors must be inserted into the correct crimp profile, and be positioned correctly. For some crimp connections, there are locators that make precise positioning simple. Control markings make it possible to check some crimp inserts after the crimp has been made and confirm whether or not the crimp has the correct profile.
• Crimping pressure should be applied evenly over the crimp profile. This is best achieved by means of a parallel crimping motion. Crimping pliers are generally adjusted for a defined crimping pressure or crimp dimension. The fact that this is also applied completely to the contact is ensured by a locking device. That means that the pliers cannot be opened until the crimping has been properly completed.

In Europe, criteria for the quality of the crimp contact to DIN standards (DIN IEC 60352-2, IEC 512, DIN EN 60999-1) include crimp width, crimp height and the pull-out force which is required to pull the conductor out of the sleeves or to tear it off. In North America, the customer and/or the terminal manufacturer specify the crimp specifications for quality acceptance. Automotive solder-less crimps generally conform to the SAE/USCAR-21 Crimp Performance Specification.  Other specifications such as UL Laboratories, Mil, or individual customer specifications apply to hand crimp tools. Soldered crimps are still permitted or required to ensure crimp reliability.

Crimp Tooling for Typical Terminal Manufacturers

Rennsteig can supply crimp die sets for various terminal manufacturers (Delphi, TYCO, Bosch, FCI, etc.). The linked Delphi terminal/die set cross-reference is typical. Die sets for other terminal manufacturers are available upon request or can be tooled for a specific customer.

Download a List of DELPHI Terminals

Rennsteig Experience

This material is made available for reference purposes only. Rennsteig assumes no liability for its usage and recommends that the user confirm results with their own crimp testing, due to the large number of interacting variables in the crimping environment and manufacture.

Crimp Tooling for Typical Terminal Manufacturers

Rennsteig can supply crimp die sets for various terminal manufacturers (Delphi, TYCO, Bosch, FCI, etc.). The linked Delphi terminal/die set cross reference is typical. Die sets for other terminal manufacturers are available upon request or can be tooled for a specific customer.

Rennsteig Crimp Technical Reference Data

Rennsteig Tools, Inc PEW 12 Crimp Tooling has been successful in meeting the SAE/USCAR 21 Crimp Performance when supplied with terminals and machine crimp information that also meets the specification. Contact us at  This email address is being protected from spambots. You need JavaScript enabled to view it. for additional information.

To purchase an official copy of the SAE/USCAR 21 specifications, visit their website by clicking here.

Crimp Curves

Well Designed Mechanical and Electrical Crimp Curves

Crimping is inherently a mechanical process that must meet electrical requirements.

X Axis: Core Crimp Height (CCH)

This crimp curve shows the typical Mechanical and Electrical parameter relationship for a well designed crimp. The main variable, once tooling, terminal and cable size are determined, is the Core Crimp Height on the X axis with increasing crimp height to the right. Typically, about seven sets of experimental test samples are needed to determine the related variables such as Crimp Cross Section (Compaction or Area Cross Sectional Reduction), Crimp Pull Off, Environmental-Low Energy Milliohm Resistance and Power Cycling Milliohm resistance. See SAE/USCAR 21-1 for test parameters.

Y Axis: Cross Section

Note that more 'voids' occur as the crimp height increases to the right, resulting in a 'loose' crimp. This looseness allows movement between the terminal and each strand resulting in an intermittently high crimp resistance. A crimp that is too tight is difficult to determine visually, but can result in low pull off value and increase resistance as the cross-sectional area of the cable is excessively reduced.

Terminal Pull Off

Note that this is a double value curve with respect to Core Crimp Height. Usually the optimum electrical results occur in a narrow tolerance range on the "up slope" of the Pull Curve. The core crimp generally becomes too loose on the down slope of the Pull-Off Curve. Terminal Pull-Off is generally only an indirect indicator of crimp electrical performance.

Environmental Electrical "Low Energy" Performance

Typically this is also a "Double Valued Curve" and is the opposite of the Pull Curve. If the cross section is too tight, the crimp resistance increases, and if it's too loose, strand movement occurs resulting in increased resistance. A narrow window of CCH will yield either acceptable maximum crimp resistance or crimp/resistance change in milliohms. The milliohm resistance is measured with a special ohm meter which restricts voltage to prevent oxide film breakdown.

Power Current Cycling

This curve is similar to the Environmental Curve but tests the current carrying capability of the crimp. See SAE/USCAR 21-1 for test parameters.

SAE & European DIN Cable

Typical Rennsteig Hand Tool Crimp Instructions (SAE and European DIN Cable)

Make sure the proper inserts, terminal holder, and wire stop are used for the intended terminal and wire gauge size. Check the tool numbers, terminal name, and wire gauge sizes on tool parts, and check the terminal part numbers and cable gauge sizes from authorized wiring diagrams or other documents. If the cable gauge size is not available, strip a sample of cable to be crimped and verify the gauge size by comparing the outside copper core diameter to the charts. (Do not distort or cut strands in the core.) Measuring the strand diameter and number of strands is a more accurate method. Use the formula for cable area (mm²) = 0.785 x (strand diameter in mm²) x number of strands if the cable is not on the chart.

USA Cable Guage Chart (SAE J1128/J1560 cable - Reference Only

European DIN Cable Chart (Reference Only)

Cable Gauge Size

Use the USA Delphi Terminals Cable Gauge Identification Reference when available. Look at the backside of the insulation crimp and read the cable size that the terminal is designed for:

MM to Inch Conversion

Instruction Videos

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