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Mindsensors Cable Crimping Tool

Author: Santiago Ricoy Email: [email protected]
Date: Last modified on 2/4/17
Keywords: Mindsensors Cable Crimping Tool NXT LEGO lego nxt cable crimper sensor EV3 ev3 6 pin RJ12 crimping tool


The video above is of myself modifying a 6-pin RJ12 connector crimping tool to allow it to crimp Lego NXT Mindsensors connector onto a 6-lane cable.

Tool Purchase Availability

Please inquire via email for either the entire crimper or just the pieces.

Motivation and Audience

This tutorial is to provide a process and file access to those searching for a clean way to modify a crimping tool to create new cables for their Lego NXT projects.

For this tutorial to be useful users should:

* Understand how to use laser cutting/3D printing files
* If you have access to cutting equipment perhaps also know how to work with vectorized images in Inkscape, Illustrator, or another related program
* Possibly understand how to modify 3D CAD models from .stl files.
* This tutorial may also attract people interested in custom cable formats

The rest of this tutorial is presented as follows; all students must understand the warnings section:

Items Required

To follow my steps in this tutorial, you'll need the following items:

6P6C Modular Crimping tool Amazon ~$20 at the time of writing 1
Angle Grinder or Metal File N/A; whichever you use N/AN/A 1
Small M3x10mm screw Harbor Freight or other N/A N/A 1
M3 Nut or locknut Harbor Freight or other N/A N/A 1
Drill and 3/16 bit for metal Any N/A N/A 1
  • Access to laser cutter/3D printer and connected computer
  • If you don't have access, a company like Ponoko or ShapeWays may help you
  • Material used: 0.11“ thick acrylic (A slightly thicker or thinner material may also work)



  • The blades for cutting and stripping cables on here are SHARP. I recommend keeping the tool closed when not being used.
  • If using an angle grinder, keep in mind that loose gloves can be extremely dangerous around the spinning blade.
  • The laser cutting file was created to account for a total 0.24mm kerf from the laser cutter; if you use another cutting machine, the kerf may be different
  • You WILL lose some functionality. Instead of the crimper having a stopper to help you choose the correct length to strip your cable, you must now manually decide how long the stripped ends should be.

Design Process

If using my files, you will not need to go through this part.

Step 1: Measurements were taken of the NXT and RJ12 connectors. This modification allows you to crimp both connectors.

Step 2: Several pieces were designed and tested in order to make a cut that was crack-resistant. Rounding all corners helped this process greatly. Adjusting laser cutter power was also necessary, but poor results came mainly from laser focusing error (I fixed this by cutting a new focusing ruler).

Step 3: Pieces were finally cut from the red acrylic.


This section gives step-by-step instructions along with photos to reference while walking through your crimper modification.

The crimper's main steel body will need to be ground down. This may be accomplished with a metal file, a small Dremel bit, a cutting wheel, etc..

In my case, I used an angle grinder after opening the tool.

Opening the tool: I ground out one of the rivets on the opening spring with a drill press and popped it out with a hammer and a nail. This will require replacement with a small screw and nut to replace it later on.

Clamping and grinding: Being careful with the blades on the tool, I opened it and placed it in a vise. I then took an angle grinder to grind out the small 1.5mmx1.5mm piece you may see in the photo above.

Entrance piece photo

Attaching the laser cut pieces: Our pieces are held together by the original screws on both sides. The two sides are easy to mix up and even put on backwards. You can see the side used for the entrance piece above. By using an NXT connector, you can easily verify which piece goes on which side, and the way it should be attached.

Reattaching the opening spring: To re-engage the opening spring, I used a 3mm screw and a nut to match it. The nut should fit snugly next to the new laser cut entrance piece. My screw ended up being too long, and I used a bolt cutter with an angle grinder to make it sit in its place nicely.

Completion: The two sides of your crimper should now look like the above photos. Please verify this before testing.

Note: *Even the original black plastic on the crimper had a tendency to crack easily. If the new acrylic pieces aren't attached correctly, they will also snap. *Test the fit of the crimper by placing an NXT connecter in the entrance piece. You should hear a click when fully engaged. *The wire stripping functionality is somewhat lost on the modified crimper; specifically, you must now manually decide the length of (RJ12 or NXT) cable that you intend to strip.


I took my cable and used the new modified crimper to attach the NXT cable connectors.


That means that they should be connected as shown.

If the cable were held flat on a surface, then one NXT connector would be upside down, and the other right-side up.

Should you not heed this method, your cable will not work.

As seen in the video, my cable actually works when it comes to NXT sensors. I tested this by creating a small program to work with a few sensors and the motors.

Final Words

This tutorial's objective was to get a student or NXT enthusiast set up with their own custom NXT cable crimper to enable them to create custom NXT cables up to 1m (possibly more) in length.

The user may want to try purchasing the NXT cable connectors, 6 pin cabling, and creating their own cables. In theory, you may also be able to create signal splitters in this case.

For questions, clarifications, etc, Email: [email protected]

mindsensors_crimping_tool_crimper.txt · Last modified: 2018/08/31 07:40 by santiagoricoy