How Do I Cut Metal Clad Cable?

Table of Contents

How To Cut Metal Clad Cable: A Comprehensive Guide

The best way to cut metal clad cable safely and effectively involves using a specialized tool like a rotary cable cutter or hacksaw, ensuring a clean cut to prevent damage to the conductors and maintaining electrical safety. Mastering this skill ensures safe and compliant electrical installations.

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Introduction: The Importance of Properly Cutting Metal Clad Cable

Metal Clad (MC) cable, also sometimes called armor clad cable, is a common type of electrical wiring used in residential, commercial, and industrial applications. Its robust metal jacket provides significant protection to the conductors inside, shielding them from physical damage and electromagnetic interference. However, this very jacket makes cutting MC cable correctly crucial. Improper cutting can damage the insulation of the internal wires, potentially leading to short circuits, ground faults, and even fire hazards. This guide will walk you through how do I cut metal clad cable safely and effectively.

Understanding Metal Clad Cable

MC cable comprises insulated conductors wrapped in a flexible metal sheath, typically aluminum or steel. This sheath serves as a grounding path and protects the wires from external forces. Different types of MC cable exist, each designed for specific applications.

MC (Metal Clad): General-purpose cable suitable for dry locations.
HCF (Health Care Facility): Designed for use in healthcare facilities and has an additional grounding conductor.
AC (Armored Cable): An older type, similar to MC cable, but typically uses a bonding strip instead of a ground wire.

It’s important to identify the type of MC cable you’re working with and understand its specific requirements before cutting.

The Right Tools for the Job

Using the correct tools is paramount for achieving a clean and safe cut. Here are some recommended tools:

Rotary Cable Cutter (MC Cutter): This is the preferred tool for cutting MC cable. It allows for a precise and clean cut without damaging the inner conductors.
Hacksaw: A hacksaw can be used, but requires more caution and a steady hand to avoid cutting into the conductors.
Cable Stripper/Armor Cutter: Useful for removing the outer jacket after cutting, to expose the wires.
Lineman’s Pliers: Needed for twisting and manipulating the metal jacket.
Screwdriver: For securing the fitting after installation.
Safety Glasses: Always wear safety glasses to protect your eyes from flying metal shards.
Gloves: Protect your hands from sharp edges.

Step-by-Step Guide: How To Cut Metal Clad Cable Using a Rotary Cutter

Mark the Cable: Use a marker to clearly indicate where you need to cut the cable.
Position the Cutter: Open the rotary cable cutter and position the cable within the cutting blades, aligning the blades with your marked location.
Close and Rotate: Close the cutter securely around the cable. Applying moderate pressure, rotate the cutter around the cable. You should hear a slight scoring sound.
Inspect the Cut: Carefully inspect the cut to ensure that the metal jacket has been completely scored, but the internal conductors haven’t been damaged. If necessary, rotate the cutter again with slightly more pressure.
Bend and Snap: Once the jacket is scored all the way around, bend the cable back and forth at the cut line until the metal jacket breaks.
Remove the Jacket: Use a cable stripper or armor cutter to carefully remove the outer jacket, exposing the insulated conductors inside. Be careful not to nick the insulation.
Install Anti-Short Bushing: Once the wires are exposed, immediately install an anti-short bushing (redhead) inside the end of the MC Cable. This provides additional protection from the cut metal end of the MC cable and the wires themselves.
Secure the Fitting: Install the appropriate fitting on the cable end, and secure the connector using a screwdriver.

Step-by-Step Guide: How To Cut Metal Clad Cable Using a Hacksaw (with Caution)

Mark the Cable: Use a marker to clearly indicate where you need to cut the cable.
Secure the Cable: Secure the cable in a vise, ensuring it’s held firmly but not crushed.
Carefully Saw: Using a hacksaw, carefully saw through the metal jacket. Apply light pressure and maintain a consistent sawing motion. Be extremely careful not to cut into the insulation of the inner conductors.
Stop Before Reaching Conductors: Stop sawing as soon as you feel the saw almost penetrating the jacket completely. You don’t want to accidentally cut into the insulation.
Bend and Snap: Similar to the rotary cutter method, bend the cable back and forth at the cut line until the metal jacket breaks.
Remove the Jacket: Use a cable stripper or armor cutter to carefully remove the outer jacket, exposing the insulated conductors inside. Be extra cautious when working with a hacksaw cut, as the edges may be sharper and more prone to damaging the insulation.
Install Anti-Short Bushing: Once the wires are exposed, immediately install an anti-short bushing (redhead) inside the end of the MC Cable. This provides additional protection from the cut metal end of the MC cable and the wires themselves.
Secure the Fitting: Install the appropriate fitting on the cable end, and secure the connector using a screwdriver.

Common Mistakes to Avoid

Cutting Too Deep: The most common mistake is cutting too deep and damaging the insulation of the internal conductors.
Using the Wrong Tool: Attempting to cut MC cable with tools not designed for the task can lead to unsafe and messy results.
Ignoring Safety Precautions: Failing to wear safety glasses and gloves can result in injuries from flying metal shards and sharp edges.
Not Securing the Cable: Insufficiently securing the cable during cutting can lead to inaccurate cuts and potential damage.
Skipping Anti-Short Bushings: Forgetting to install anti-short bushings increases the risk of short circuits.

Importance of Proper Grounding

The metal jacket of MC cable serves as a crucial grounding path. When cutting and installing MC cable, ensure that the grounding path remains intact. Proper grounding protects against electrical shocks and reduces the risk of fire. Using the correct fittings and ensuring secure connections are vital for maintaining a reliable grounding system.

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Frequently Asked Questions (FAQs)

Is it safe to use a utility knife to cut MC cable?

No, it is not safe to use a utility knife to cut MC cable. Utility knives are not designed for cutting through metal and can easily slip, causing injury to yourself or damage to the conductors within the cable. Using a specialized rotary cutter or, with care, a hacksaw, is essential for safety and precision.

What is the purpose of the anti-short bushing (redhead)?

The anti-short bushing, often referred to as a “redhead” due to its typical red color, serves as a protective barrier between the sharp edges of the cut metal jacket and the insulated conductors inside. It prevents the insulation from being damaged, which could lead to short circuits or ground faults.

Can I use regular wire strippers to strip the wires inside MC cable?

While you can use regular wire strippers, it’s often safer to use strippers specifically designed for electrical wiring. These strippers are calibrated to avoid nicking or damaging the conductors, ensuring a reliable and safe connection. The key is to use the correct gauge setting.

How tight should I tighten the screws on the MC cable fitting?

The screws on the MC cable fitting should be tightened snugly, but not overtightened. Overtightening can damage the cable jacket and potentially compromise the grounding path. Follow the manufacturer’s torque specifications for the fitting.

What if I accidentally nick the insulation of a wire inside the MC cable?

If you accidentally nick the insulation of a wire, it’s crucial to repair it. You can use electrical tape to carefully wrap the damaged area, ensuring that the exposed conductor is completely covered. If the nick is severe, it’s best to replace the damaged section of the wire.

Do I need to use a special type of fitting for MC cable?

Yes, you must use fittings specifically designed for MC cable. These fittings provide a secure connection and maintain the integrity of the grounding path. Using the wrong type of fitting can compromise the electrical safety of the installation.

What is the difference between MC cable and AC cable?

Both MC (Metal Clad) and AC (Armored Cable) provide metal sheaths for circuit conductors. The main difference is that AC cable typically uses a bonding strip, while MC cable uses a dedicated grounding conductor. Always verify the type of cable before working with it to ensure proper grounding.

What size MC cable do I need for a specific application?

The size of the MC cable needed depends on the amperage of the circuit and the distance the cable needs to run. Consult the National Electrical Code (NEC) or a qualified electrician to determine the appropriate size for your specific application. Improper cable sizing can lead to overheating and fire hazards.

Is it necessary to deburr the cut end of the MC cable jacket?

Yes, it is highly recommended to deburr the cut end of the MC cable jacket. Deburring removes any sharp edges that could damage the insulation of the wires or cause injury during installation. A file or deburring tool can be used for this purpose.

Can I reuse MC cable that has been previously installed?

Reusing MC cable is generally not recommended, especially if you’re unsure of its condition. The cable may have been damaged during previous installation or exposure to environmental factors. It’s best to use new MC cable to ensure a safe and reliable electrical connection.

What should I do with scrap pieces of MC cable?

Scrap pieces of MC cable should be disposed of responsibly. Contact your local recycling center or waste management facility to determine the proper disposal methods. Recycling the metal from the cable is an environmentally friendly option.

How often should I inspect my MC cable installations?

MC cable installations should be inspected periodically to ensure that the cable and fittings are in good condition and that there are no signs of damage or corrosion. Regular inspections can help prevent potential electrical problems and ensure the safety of your electrical system.