How to Use a Crimper Tool | Solid Connections Every Time

Using a crimper tool means matching the correct die to your connector and wire, then squeezing until the ratchet releases to form a permanent, inspectable connection.

Knowing how to use a crimper tool correctly is the difference between a connection that lasts for years and one that fails at the worst possible moment. The process is simple, but it demands precision: the right die size, a cleanly stripped wire, and a complete squeeze of the handles. Skip a step, and you get a loose joint that can overheat or pull apart.

Choosing The Right Die And Wire

The selection of the die set, connector, and wire size is not a suggestion—it’s a requirement. Every manufacturer, including TE Connectivity and Milwaukee, specifies that the wire gauge and insulation diameter must fall within the connector’s stated range for the crimp to hold.

The steps here are straightforward but critical:

• Select the correct terminal or splice for your wire size, not just one that looks close.
• Pick the matching die set from your tool’s available options—using the wrong die deforms the barrel and ruins the connection.
• Install both die halves securely into the tool head before you begin; loose dies produce crooked crimps.
• Strip the wire to the specified length without nicking or cutting any strands. Damaged strands compromise the crimp’s strength, and a wire that’s stripped too long can short against other terminals.

Nicked or missing strands are a hard failure point. If your strip job cut into the copper, cut the wire back and start over—a crimp on damaged strands will fail under load.

Positioning The Terminal And Wire

Placement inside the tool determines whether the finished crimp is straight, centered, and secure. The wire has to bottom out inside the barrel, and the terminal has to sit correctly in the die cavity before any pressure is applied.

For most hand tools, you’ll place the terminal in the die with the barrel facing up. TE Connectivity’s procedure specifies you should insert the stripped wire into the terminal barrel until it bottoms out—there should be no movement when you tug it gently. On a ratcheting tool, close the handles just enough to hold the terminal in place without deforming the barrel, then insert the wire. This keeps everything aligned while you position your hands for the final squeeze.

Completing The Crimp Cycle

With everything positioned, the actual crimping is one deliberate motion. Squeeze the handles with consistent, steady pressure until the ratchet mechanism releases or the full cycle completes. This ratchet release is not a suggestion—it’s the tool’s way of guaranteeing the die has closed completely and the crimp is fully formed. TE Connectivity’s manual stresses allowing the handles to open fully before removing the crimped terminal from the die.

For hydraulic and powered crimpers, the same principle applies in a different form:

• Hydraulic tools: crank or pump the handle to advance the piston until the terminal is fully crimped, then rotate the release valve to retract the piston before removing the work.
• Powered tools like Milwaukee’s M18 FORCELLOGIC: insert and hand-tighten the locking thumb screw to secure the head, then rotate the jaws to your desired angle before triggering the cycle.
• Always wear safety glasses. Crimper jaws can pinch severely, and the tool itself can slip under load.

When the cycle finishes, inspect the crimp. A good one has a clean, symmetrical indentation centered on the barrel, with no visible gaps between the wire and the terminal. Give it a firm tug—the wire must not pull free. If it moves, the crimp has failed; cut the terminal off and start again.

Final Crimp Checklist And Buying Your Own

The complete process boils down to a handful of non-negotiable steps. Run through them in order, and you’ll never wonder whether a connection is going to hold:

• Match the die, connector, and wire size to the manufacturer’s spec.
• Strip the wire cleanly to the exact length—no nicks, no missing strands.
• Seat the terminal in the die and bottom out the wire in the barrel.
• Squeeze with steady pressure until the ratchet releases.
• Open the handles fully, remove the crimp, and inspect the indentation.
• Tug-test the connection to confirm it’s permanent.

The principles stay the same whether you’re working with a manual tool or a powered unit. For high-volume or heavy-gauge work, a battery-powered crimper saves your hands and speeds the job considerably. If you’re ready to invest in one, our tested roundup of the best battery crimper tools on the market breaks down the top performers by power and price. The ratchet release is your final confirmation—when it clicks, the crimp is done.