Mechanical and Hydraulic Benders: IMC and RMC

Mechanical and Hydraulic Benders: IMC and RMC

Why These Benders?

Intermediate Metal Conduit (IMC) and Rigid Metal Conduit (RMC) are heavier, thicker-walled than EMT. Their wall strength resists crushing and protects conductors in exposed, wet, or high-abuse locations — but that same wall thickness demands far more bending force. A hand EMT bender cannot produce a clean bend in 1″ IMC or RMC without kinking or flattening the conduit. Instead, electricians use mechanical (Chicago-type) benders for IMC and hydraulic benders for heavier RMC work. Understanding when and how to use each machine is a core field competency.

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Mechanical (Chicago-Type) Bender

The Chicago-type bender is a floor-standing mechanical machine. A forming shoe — sized to the conduit diameter — is mounted on a pivot arm. The operator advances the shoe around the conduit by pressing on a foot pedal or handle, applying controlled leverage. The follow bar (also called the follow block or pressure block) holds the conduit against the shoe and prevents the outside wall from collapsing. The pipe hook keeps the conduit from sliding backward during the bend.

Shoe fit matters. Using the wrong shoe size causes rippling, kinking, or an oval cross-section. Confirm the shoe is stamped or tagged for 1″ IMC before bending.

Pre-operation inspection — mechanical bender:

• Shoe: No cracks, chips, or excessive wear grooves. Verify size match.
• Follow bar: Moves freely, no binding; pivot pins not worn.
• Pipe hook: Present, functional, correct size.
• Bending table/frame: Level and stable on the shop floor (use a torpedo level on the frame).
• Mechanical linkage and foot pedal: Moves smoothly; no bent or cracked parts.

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Hydraulic Bender

A hydraulic bender uses a pump — hand-operated or electric — to force hydraulic fluid against a ram, which pushes a forming die into the conduit. Hydraulic multiplication of force makes bending 1″ and larger RMC straightforward. RMC has the thickest wall of any metallic conduit system; it requires significantly more force than IMC of the same trade size.

Pre-operation inspection — hydraulic bender:

• Fluid level: Check the reservoir sight glass or dipstick; low fluid causes the ram to stop short and produces an incomplete bend.
• Ram seal: Inspect for hydraulic fluid leakage around the ram. A weeping seal will lose pressure mid-bend; a leaking seal is a safety and housekeeping hazard — tag the unit out of service and notify the instructor.
• Die fit: Confirm the die (or shoe) is rated for 1″ RMC and is seated correctly in the ram and saddle. A loose die can shift violently when pressure is applied.
• Hose and fittings: No cuts, abrasion, or bulging on hydraulic hoses.
• Release valve: Operates freely; can be opened quickly if conduit needs to be released.

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Safety — Both Machines

Apply lockout/tagout (LOTO) procedures before inspecting, cleaning, or changing dies on either machine. Required PPE for all bending operations: safety glasses, leather gloves, and steel-toed boots. Keep fingers and hands clear of the bending shoe and die during any powered stroke. Never stand directly in line with the conduit run — if the conduit slips, it can whip. Maintain a clear work zone; trip hazards from conduit stock on the floor cause injuries.

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Bending a 90-Degree Stub: IMC on the Mechanical Bender

A stub-up (or stub-90) creates a vertical rise from a horizontal conduit run. The key measurement is the stub height — measured from the end of the conduit to the inside of the 90° bend.

Deducting for the bender gain: Every bender shoe has a gain (also called take-up) — the amount of conduit used up forming the curve. For a 1″ mechanical bender shoe, consult the manufacturer's stamped value or the bender chart. The gain is typically printed on the shoe itself. Mark the conduit at: desired stub height minus the gain, measured from the end. Place this mark at the arrow or start-of-bend mark on the shoe, then bend to 90°.

After bending, measure the stub height from the end of the conduit to the inside of the bend. The acceptable tolerance for this lesson is ±¼″ in height and ±2° in angle.

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Bending an Offset: RMC on the Hydraulic Bender

An offset shifts the conduit run to a parallel path at a different elevation. A 30° offset is common because it keeps the conduit close to the surface and the math is straightforward.

For a 30° offset with a desired height (rise) of 6":

• Mark-to-mark distance = rise ÷ sin(30°) = 6 ÷ 0.5 = 12″

Mark the first bend location, bend to 30°, then measure 12" along the conduit and mark the second bend location. Roll the conduit 180° (rotate it so the second bend curves the opposite direction), align the second mark to the bender, and bend to 30°.

After bending, measure offset height and confirm the two straight sections are parallel (use a combination square or lay both ends flat on the bench). Acceptable tolerance: ±¼″ height.

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Why RMC Needs Hydraulic Power

RMC wall thickness is greater than IMC, which is in turn greater than EMT. The force required to bend conduit increases with wall thickness and material cross-section. Attempting to bend 1″ RMC on a mechanical bender rated only for IMC risks damaging the machine, kinking the conduit, or injuring the operator. Hydraulic benders generate controlled, consistent high force — making clean, repeatable bends in heavy conduit practical and safe.