How to Use a Wire Crimping Tool | Proper Crimp Technique

A bad crimp causes intermittent failures, voltage drops, and fire hazards. The good news: the technique itself is straightforward once you match the tool, connector, and wire size correctly. The steps differ slightly for insulated terminals versus non-insulated ones, and ratcheting tools enforce consistency that manual tools leave to your hand strength. Here is how to do it right the first time, every time.

Select the Right Tool and Connector Match

The crimping tool and the connector must be sized for the wire gauge you are using. Most ratcheting crimpers have color-coded die cavities or stamped gauge markings that correspond to common connector colors (red for 22–18 AWG, blue for 16–14 AWG, yellow for 12–10 AWG). Using the wrong cavity deforms the barrel unevenly and produces a weak joint.

Connectors themselves also come in families. Insulated terminals have a colored nylon sleeve, non-insulated terminals are bare metal, and wire lugs require different die profiles. TE Connectivity’s guide stresses that the correct die cavity depends on both wire gauge and connector style — a universal one-size-fits-all approach fails with specialty terminals like splices or butt connectors.

When you are ready to pick the right tool for your job, our tested wire terminal crimping tool roundup compares the ratcheting models that produce consistent results across the most common connector families.

How to Strip Wire for Crimping

Strip the insulation to the exact length the connector requires — typically about 1/4 inch for common insulated terminals, but check the connector’s packaging or datasheet. The exposed conductor should fill the wire barrel completely without leaving a gap, and the insulation should stop at the insulation support area rather than entering the wire barrel.

• Use a dedicated wire stripper, not a knife or side cutters. Nicked strands create stress risers that crack under vibration.
• Remove insulation cleanly without stretching or tearing the remaining jacket.
• If you expose too much conductor, trim the excess flush with the barrel end — bare wire sticking past the connector invites shorts.

Crimp the Connector: Step by Step

The procedure that applies to most standard terminals and splices comes directly from TE Connectivity’s Certi-Crimp method. The sequence works for both insulated and non-insulated styles, with one extra step for splices.

1. Place the terminal in the tool. Orient it so the tongue goes under the locator (for terminals) or the center window indent sits under the locator (for splices). Close the handles just enough to hold the connector without deforming the barrel.
2. Insert the stripped wire. Push it in until the conductor bottoms out at the end of the wire barrel or reaches the inspection window. The insulation should meet the barrel entrance — not enter it.
3. Squeeze fully. For ratcheting tools, close the handles all the way until the ratchet releases with an audible click. Do not stop early or try to release the ratchet manually — an incomplete cycle produces an undersized crimp.
4. For splices only: Rotate the assembly 180 degrees and crimp the other half of the barrel. This creates two compression zones for a secure through-joint.
5. Inspect the result. A proper crimp shows a visible bell mouth at the insulation end, no cracked barrel, and no nicked strands protruding from the connector. Perform a pull test: the wire should not slide out when you tug firmly by hand.