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General Info

Visual Inspection of Crimp Connections


Please click the link below to get detailed information about inspection of crimp connections.

Open inspection overview.
Open inspection overview

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 (The pull-out force is defined in a standard relative to the cross-section of the conductor and represents a minimum value which must be satisfied by the correct dimensions of the crimp sleeve and the correct compression of the conductor.). 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
Adobe PDF

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.

Electrical Crimp Curves


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 Gauge Chart (SAE J1128/J1560 cable - Reference Only

Cable Size
AWG 22 20 18 16 14 12 10
Metric (mm2) 0.35 0.50 0.80 1.00 2.00 3.00 5.00
Number of Strands771919191919
Min Strand Diameter
mm 0.423 0.304 0.226 0.275 0.353 0.443 0.559
inch 0.0096 0.120 0.0089 0.0108 0.0139 0.0174 0.0220
Nom Strand Diameter
mm 0.247 0.308 0.230 0.279 0.357 0.447 0.563
inch 0.0097 0.0121 0.0091 0.0110 0.0141 0.0176 0.0222
Copper Core Outside Diameter
Millimeters 0.75 0.92 1.14 1.38 1.77 2.23 2.81
0.030 0.036 0.045 0.054 0.070 0.088 0.111

European DIN Cable Chart (Reference Only)

Cable Size
Metric (mm2) 0.35 0.50 0.75 1.00 1.50 2.50 4.00 6.00
Number of Strands12 or 716 or 1924 or 1932 or 1930 or 1950 or 195684
Max. Strand Diameter
mm 0.21 or 0.26 0.21 or 0.19 0.21 or 0.23 0.21 or 0.26 0.26 or 0.32 0.26 or 0.41 0.31 0.31
Copper Core Outside Diameter (MAX)
Millimeters 0.90 or 0.26 1.10 or 0.19 1.20 or 1.20 1.35 or 1.35 1.70 or 1.70 2.20 or 2.20 2.75 3.30

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:

Example Terminal with Number

Terminal Gauge Size MM2 Gauge Size AWG
21 0.35 & 0.50 22 & 20
19 0.50 & 0.85 20 & 18
15 1.00 & 2.00 14 & 16
13 2.00 & 3.00 14 & 12

MM to Inch Conversion

MM Approx Inches
100 4"
110 4 1/4"
115 4 1/2"
120 4 3/4"
125 5"
135 5 1/4"
140 5 1/2"
145 5 3/4"
150 6"
160 6 1/4"
165 6 1/2"
175 - 180 7"
185 - 190 7 1/2"
200 8"
254 9"
250 10"
275 11"
300 12"
325 13"
350 14"
400 16"
450 18"
500 20"
600 24"

Instruction Videos


We started to provide step-by-step instruction videos for our customers to show everyone how easy it is to work with our tools. Visit Our YouTube Channel! Click on the link below and see our tools in action!

http://www.youtube.com/user/RennsteigToolsInc or checkout here.

You did not found the right product on our channel so please let us know what you would like to see in one of our next videos. Send an email to This email address is being protected from spambots. You need JavaScript enabled to view it. . Our goal at YouTube is to help you do a professional job with quality tools from RENNSTEIG.

Dielectric Strength


Dielectric StrengthDielectric strength is the insulating characteristic of a material which prevents voltage breakdown or flashover. It is measured at voltage per millimeters of the insulation thickness.

Dielectric strength is also influenced by the deformation which occurs when an insulated connector is crimped. Then insulation may not be damaged here.


Gas tight


What does gas-tight mean?

As a gas-tight connection is one where the conductors and connectors are so tightly deformed and compressed together that there are no cavities between them. Neither a liquid nor a gas-type medium can penetrate the crimp in normal atmospheric conditions.

Oxidation between the compressed individual wires is suppressed and any increase in the crimp transition resistance is almost impossible.

In some cases it is possible that isolated cavities will still occur. As a result of the fact that the cable is twisted, however, these cavities may be regarded as self-sealed. A dense crimp can be tested using a section. The section level is ideally in the middle third of the conductor crimp sleeve and between the compressed grooves.

Where compression is insufficient

  • The conductor can be pulled out of the connection
  • Cavities can remain in which oxidation can take place

Oxidation increases transfer resistance.

Increased resistance is disadvantageous for

  • Signal transmission because it attenuates (weakens) the signal flow
  • Power transmission because energy is lost and contacts are heated (risk of fire)

Where compression is sufficient, the individual conductors are pressed tightly together and deformed. This allows compression without the formation of any appreciable cavities.

Compression is insufficient Compression is sufficient
Compression is insufficient Compression is sufficient

Tools for GM in practical use



Check out this excellent source of information written by Mike Noonan. This book contains exactly the info you need if you plan the use of a modern GM PCM for my older vehicle / muscle car. It's not just another "LS" engine swap manual. The book also features plenty of photos of factory tools and side-by-side comparisons with our products. (Chapter 13)

It’s a great example how to use our tools. 

All listed tools can be purchased here:

The publication can be purchased here:

© 2011 by Rennsteig Tools, Inc. | Disclaimer | Terms of Use | Warranties | Terms and Conditions

Product images are for illustration purposes only and may differ from the actual product.
Registered Trademarks: MC® / MC3® / MC4® = Multi-Contact AG | Solarlok® = Tyco Electronics | Radox® = Huber+Suhner | SunCon™ = Hirschmann | gesis® = Wieland
AMP, Tyco, TE Connectivity = Tyco International Service GmbH