How to Crimp Wires

Posted on Jan 21, 2020 by Robert Iversrud

shutterstock_1545705365-1Crimping is a common method for compressing a terminal to a wire conductor without the use of soldering. When done correctly, a crimp creates a mechanically sound connection that resists corrosion, gas, and liquids.

If you’ve ever crimped a terminal to a wire, you know that it’s not the most glamorous of tasks. Seemingly simple, all you have to do is strip back the wire, put a terminal on the end, grab the nearest tool and clamp down until the terminal stays on the wire. Right?

Not exactly.

One bad crimp can lead to major equipment failures, resulting in time-consuming diagnostic testing and costly repairs.

We put together three simple steps on how to master the perfect crimp:

  1. Prep
  2. Crimp
  3. Inspect

Follow these steps, and you’re sure to prevent poor crimps and weak connections from deterring your projects.

How to Crimp Terminals in 3 Steps

Step 1: Prep

Don’t skip prep! Preparation sets up your crimp for success. Start by using a proper wire stripper to strip the wire. 


Not all terminals are created the same, so we recommend checking with the terminal’s manufacturer for the recommended strip length for the terminal.

Strip Length-1

Set your tool accordingly and strip the wire.

Wire Crimp - Ampacity

Once the outer jacket is stripped, ensure the wire strands are not cut or nicked-which can reduce the ampacity of the conductor and shorten the lifespan of the connection.

Wire Crimp - 2

Step 2: Crimp

The main benefit of crimping is that it eliminates the need for soldering wire, therefore reducing installation Crimp Article Side Bar - 1time.

This reduction in time is very important in today’s market where time is of the essence and fewer technicians are being asked to maintain more and more equipment. In addition, solder joints are brittle and are prone to failure under continual vibration, which can be expected in harsh environments.

To be sure your crimp goes smoothly, use the terminal manufacturer’s recommended tools. You may be tempted to grab whatever tool is within arm’s reach, but every manufacturer designs their terminals to be crimped with a specific set of tooling. Using the incorrect tools could cause crimps to not meet the designated specs and open you up to potential failure.

Many customers like using ratcheting crimp tools because they provide tactile feedback so you know when the terminal crimp is fully compressed. Ratcheting crimp tools also assure a proper crimp by providing a color coded, visual confirmation that you are using the correct cavity for the gauge wire you are crimping. Lastly, they don’t allow you to open the crimp jaws until you’ve reached proper crimp height.

Wire Crimp - 3

Once the crimp is complete, it’s time for testing to ensure a strong connection.

Step 3: Inspect  Wire Crimp -4

You’ve put in the effort to prep and crimp correctly, so finish it out with testing or inspection to be sure your connection lasts.

There are three differences between good and bad crimps:

  1. Crimp location
  2. Strand compression
  3. Voids between strands

Start by visually inspecting crimps with a magnifying glass for any obvious flaws.

The conductor crimp should be centered on the conductor barrel, which insures even pressure on the entire length of the barrel.

Be sure that wire strands do not exceed into the tongue area of the lug or terminal.

Be sure that the wires are either flush with the end of the conductor barrel or extend past the barrel ever so slightly. 

Next use a crimp micrometer to measure crimp height and width. Measuring the crimping height of the crimped terminals at the center of the wire barrel and at the center of the insulation barrel, verify the crimp is within range specified by the manufacturer. This measurement of the height of the terminated wire in the crimp area is a good method of quality control as it is non-destructive.

Wire Crimp - 5

Wire Crimp - 6Lastly–and save this test for a sample crimp only–use a wire crimp pull tester to make sure the crimp stands up to the tensile strength that the manufacturer specifies when properly crimped. This test is destructive so it should only be performed on a sample crimp to prove you are hitting spec.

Wire Crimp - Tensile Strength

Follow the above steps and you've mastered the perfect crimp.

Shop our crimp tools from Molex and more at WaytekWire.com.