How To Cut Flexible Conduit: A Step-by-Step Guide For FMC, LFMC, And LFNC

To cut flexible conduit safely and cleanly, you must select the appropriate tool based on the material: a specialized rotary cutter (such as a Rotex tool) for Flexible Metal Conduit (FMC), a fine-toothed 32 TPI hacksaw or bandsaw for Liquidtight Flexible Metal Conduit (LFMC), or a ratcheting plastic pipe cutter for Liquidtight Flexible Nonmetallic Conduit (LFNC). Achieving a perfectly square, burr-free edge is critical to ensure fitting engagement, preserve the water-tight seal, and protect internal conductors from insulation damage. All cuts must conform to National Electrical Code (NEC) standards, specifically regarding deburring and the installation of anti-short bushings.

Essential Safety Protocol and Equipment Checklist for Conduit Preparation

Before executing any electrical rough-in work involving flexible conduit, preparation is key. Selecting the wrong cutting method can damage the internal spiral shielding of metal conduits, flatten the profile of non-metallic materials, or leave sharp, jagged metal burrs that easily slice through wire insulation during pulling.

To ensure compliance with National Electrical Code (NEC) Article 348 (FMC), Article 350 (LFMC), and Article 356 (LFNC), you must assemble the correct array of tools and protective equipment.

Required Gear, Tools, and Material Inventory

• Rotary Conduit Cutter: Specifically designed for metallic flexible conduit (such as Seatek or Southwire Rotoflex), this tool secures the conduit and cuts only the outer metal rib without touching internal conductors.
• Hacksaw: Fitted with a high-carbon steel 32 Teeth Per Inch (TPI) blade. Do not use blades with lower TPI counts, as they will snag and deform the metallic spirals.
• Ratcheting PVC/Plastic Shear Cutter: Ideal for producing clean, square cuts on non-metallic (LFNC) conduits up to 2 inches in diameter.
• Deburring Tool or Half-Round File: Essential for smoothing down sharp edges on metal conduits.
• Anti-Short Bushings (Red Devils): High-dielectric plastic inserts designed to slide into the cut ends of FMC to safeguard conductors.
• Safety Equipment: ANSI-approved Z87.1 safety glasses, cut-resistant work gloves (ANSI Level A3 minimum), and a dust mask for plastic debris.

Technical Benchmarks and Specifications

• Estimated Duration: 1 to 3 minutes per cut, depending on the tool and conduit diameter.
• Project Budget: $15 to $75 depending on whether you purchase a manual hacksaw or a professional-grade rotary cutter.
• Required Clearance: Ensure a minimum of 6 inches of straight, unbent conduit on either side of the cut line to guarantee a square, undistorted cut.

Execution Guide: Cutting Flexible Metal, Liquidtight Metal, and Nonmetallic Conduit

To achieve a professional-grade cut that preserves the structural integrity of the conduit and complies with local building codes, follow these specific step-by-step methodologies based on your exact conduit type.

Step 1: Measure and Mark the Cut Point

Accurate measurement prevents material waste and ensures you maintain the minimum bending radius required by the NEC. Use a high-visibility marker or grease pencil to place a clean, circumferential line around the conduit.

When planning your cuts, account for fitting "take-up"—the physical depth inside the connector body where the conduit bottoms out. Measure the interior depth of your connector (typically 1/2 inch to 3/4 inch) and add this dimension to your overall run length before marking.

Step 2: Cutting Flexible Metal Conduit (FMC) with a Rotary Cutter

The rotary cutter is the industry standard for FMC (commonly referred to as Greenfield). This method is highly recommended because it is fast, precise, and completely eliminates the risk of crushing the conduit profile.

1. Open the clamping channel of the rotary cutter by releasing the thumb screw or spring-loaded lever.
2. Position the conduit inside the channel, aligning your mark directly beneath the circular cutting blade.
3. Squeeze the tool handle to depress the blade against the conduit. Adjust the depth-adjustment screw so that the blade will penetrate only the thickness of one metal rib, preventing it from piercing through the center of the conduit.
4. Rotate the hand crank or spin the tool body around the conduit clockwise two to three full turns. You will feel a sudden drop in resistance as the blade cuts through the outer metal rib.
5. Remove the tool. Grasp the conduit on both sides of the cut and gently bend it back and forth. The cut spiral will snap apart cleanly.
6. Twist the waste piece counter-clockwise to separate the two halves.

Pro-Tip: Never force or over-tighten the blade depth on a rotary cutter. Excessive pressure will dull the carbide blade prematurely and crush the underlying steel or aluminum armor, making it impossible to insert an anti-short bushing.

Step 3: Cutting Liquidtight Flexible Metal Conduit (LFMC) with a Hacksaw

LFMC (often called Sealtite) features an internal spiral metal core encased in a thick, waterproof polyvinyl chloride (PVC) jacket. Rotary cutters cannot easily slice through this outer jacket, making a fine-toothed hacksaw the preferred manual tool.

1. Secure the LFMC inside a portable pipe vise or a miter box. Secure clamping is critical; if the conduit slips during cutting, the PVC jacket will tear, destroying its liquid-tight properties.
2. Position your 32 TPI hacksaw blade directly on your mark. Hold the blade perpendicular (90 degrees) to the conduit.
3. Begin cutting with light, forward strokes. Avoid downward pressure; let the teeth of the blade slowly score the outer PVC jacket.
4. Once the jacket is breached, continue sawing through the metal spirals using steady, full-length strokes.
5. As you near the end of the cut, support the suspended end of the conduit with your free hand to prevent the final section of the PVC jacket from tearing or stretching under its own weight.

Warning: Do not use a reciprocating saw (Sawzall) with a standard metal blade for cutting flexible metal conduit unless you are using a specialized, high-speed, ultra-fine-tooth metal blade and a clamping shoe attachment. The violent back-and-forth action of a reciprocating saw can easily snag the metal spirals, unraveling the conduit and posing a serious kickback hazard.

Step 4: Cutting Liquidtight Flexible Nonmetallic Conduit (LFNC)

LFNC consists of a smooth inner wall with integral reinforcement embedded within the conduit wall. Because it contains no metal, a shearing action yields the cleanest results.

1. Insert the LFNC into the jaw of a ratcheting PVC cutter, aligning the blade with your cut mark.
2. Squeeze the handles repeatedly to engage the ratcheting mechanism, driving the blade through the material.
3. Keep your hand steady to ensure the blade passes straight through. A diagonal cut will prevent the conduit from bottoming out inside the liquid-tight fitting, which compromises the moisture seal.
4. Inspect the cut end. If the pipe wall collapsed slightly during the cut, insert the nose of a pair of needle-nose pliers into the opening and rotate it to restore the round profile.

Step 5: Deburring, Finishing, and Installing Anti-Short Bushings

Every cut on a metallic conduit leaves sharp edges. Failing to deburr these edges violates NEC Article 348.28 and can lead to immediate electrical shorts when conductors are pulled.

1. Use a half-round file or a specialized conduit reamer to remove all sharp burrs from the inside and outside circumference of the cut metal armor.
2. For FMC installations, select an appropriately sized anti-short bushing (typically Red, sized #0 for 5/16", #1 for 1/2", or #2 for 3/4" conduit).
3. Tuck the tapered end of the plastic bushing inside the cut end of the metal armor. The wide flange of the bushing must sit flush against the cut metal edge, creating a smooth plastic shield over the sharp steel or aluminum.
4. Thread your fitting onto the conduit over the bushing. Tighten the collar until secure, confirming visually that the red bushing remains fully visible and intact.

Flexible Conduit Material Properties and Cutting Methods Comparison

Field Issues, Deformation, and Remedial Actions

Issue 1: The Spiral Metal Core of FMC is Unraveling

• Root Cause: The cut was executed using a coarse-toothed blade (such as an 18 TPI hacksaw or wood-cutting saw), which caught the edge of the spiral and pulled it out of its interlocking track.
• Actionable Fix: Cut off the unraveled section at least 3 inches back from the damaged area. Remake the cut using a dedicated rotary cutter or a fine 32 TPI blade, applying light pressure and keeping the blade strictly perpendicular to the run.

Issue 2: The Liquidtight Fitting Fails to Seat or Leak-Test Properly

• Root Cause: The cut on the LFMC or LFNC was made at an angle, preventing the internal nylon compression ferrule from seating flush against the cut face of the conduit.
• Actionable Fix: Remove the fitting. Use a miter box or a ratcheting shear cutter to trim the conduit end perfectly square (90 degrees). Re-clean any burrs, slide the compression nut and ferrule back on, and torque the fitting to the manufacturer's specifications.

Issue 3: The Conduit Wall Collapsed and Flattened During the Cut

• Root Cause: Excess pressure was applied with manual pliers-style cutters, or a dull blade was forced through the conduit without letting the tool do the work.
• Actionable Fix: Cut away the deformed section. If cutting LFNC, switch to a sharp, ratcheting cutter. If cutting FMC or LFMC, avoid using standard hand shears; use a rotary cutter or a high-speed bandsaw with minimal downward pressure.

Frequently Asked Questions

Do you need anti-short bushings for all flexible conduit installations?

According to National Electrical Code (NEC) Article 348.26, anti-short bushings are required at all termination points of Flexible Metal Conduit (FMC) unless the fitting itself is specifically designed and listed to provide equivalent protection. Even when not strictly mandated by a specific fitting design, using "Red Devil" bushings is considered an industry-wide best practice to prevent wire insulation failures.

Can you cut liquid-tight conduit with a standard utility knife?

A utility knife should never be used to cut the metallic core of LFMC, as it cannot slice through steel. While you can use a utility knife to cut non-metallic LFNC, it is highly discouraged because the blade can easily slip, causing severe personal injury or resulting in an uneven, diagonal cut that compromises the liquid-tight rating of the connector.

What is the easiest way to cut Flexible Metal Conduit (FMC) without a specialized tool?

If you do not have a rotary cutter, the best alternative is a hacksaw fitted with a 32 TPI blade. Secure the conduit firmly in a vise, score the metal armor diagonally across one of the spiral ribs, and then twist the conduit to snap it open. File down the internal and external sharp edges immediately.

How do you prevent flexible conduit from unraveling when cut?

To prevent unraveling, secure the conduit tightly close to the cut mark to limit vibration. Use a high TPI blade and apply light, rapid strokes. If cutting highly flexible or worn conduit, wrap a single layer of electrical tape tightly around the cut line before sawing, and cut directly through the center of the tape to hold the metal spirals in place.

Upgrade Your Electrical Tooling and Efficiency

Precision preparation is the difference between a secure, code-compliant electrical installation and a hazardous system failure. Invest in professional-grade rotary cutters and premium anti-short bushings today to ensure your conduits are safe, watertight, and built to last.