Contractor turns a Milwaukee Hackzall into a portable Ethernet untwister

A huge cabling job sparked the project

A contractor behind the YouTube channel Analytical Horsepower faced a project that required 50,000 custom Cat6 cables, which means 100,000 RJ45 terminations, according to Tom's Hardware. Untwisting the four twisted pairs inside each cable by hand is slow, so he looked for a faster way.

His first solution was a wire straightening machine bought from Alibaba for $500. It works well, but it is an industrial tabletop device that needs mains power and compressed air, which is awkward on a jobsite.

First attempt: a portable but bulky machine

To make the bought machine portable, the contractor rebuilt it. He replaced the DC power brick with a 20V DeWalt battery and an adapter, added a push-button switch for power, and used a portable bike pump to supply compressed air in the field.

The machine clamps the cable between two rubber grips using air pressure, and a linkage converts the motor's rotary motion into a linear one, so the grip untwists the cable. It worked, but the tool was too bulky for the tight spaces where Ethernet cables often terminate, such as installations near outdoor Wi-Fi 7 access points.

Rebuilding the idea around a Hackzall

Having studied the concept, he realised the job only needed a reciprocating tool with a clamp attached. Two flat, grippy surfaces grab the twisted cable and move back and forth, untwisting the pairs while the clamping force keeps contact as the cable flattens.

A standard reciprocating saw was still too bulky and, in his view, not precise enough. The Milwaukee Hackzall offered a better balance of portability and control. Its detailed data sheet, instruction manual and parts breakdown let him make accurate plastic and metal parts, printed and laser-cut and bent to fit. A toggle clamp holds the Cat6 cable instead of a pneumatic piston, which simplified the design and cut its size and weight.

After trial and error, mostly with the grippy clamping materials, the tool worked. It reliably untwists softer copper-clad aluminium cables in one pass in under two seconds. Stiffer 100% pure copper conductors must be done pair by pair, which takes longer but is still far faster than using bare hands.

Who benefits and what could improve

Tom's Hardware notes the tool is not worthwhile for someone who untwists only a few cables a month. But on a job of this scale, saving half a minute per cable end could add up to more than 830 hours of labour saved.

Commenters on the video suggest lengthening the toggle clamp handle so it can reach the trigger, making the tool easier to operate. Another idea raised there is building the whole mechanism into a crimper. The site calls it a strong first-generation tool, though these suggestions remain ideas from viewers rather than tested designs.