The variety of electrical installations makes field bending necessary. While a full range of factory elbows are readily available, they do not address the variability of stubs, back-to-back, offset, and saddle bends encountered in the field-routing of conduit and EMT. These most commonly used types of bends can be quickly, efficiently, and economically made by a knowledgeable and experienced installer. The skills needed to obtain a level of proficiency are readily learned and require knowledge of basic mathematics, industry terminology and bending tools. Manufacturers of bending equipment publish manuals for each specific bender model which provide excellent in-depth information on bending conduit. The information in this section is supplemental to that provided by the manufacturers. Contact bender manufacturers for complete information.
|Table 2: Proper Wrench Size|
|Conduit Trade Size||Wrench Size|
|3/4 through 1 1/4||14"|
|2 - 2 1/2||24"|
|3 – 4||36"|
|5 – 6||48"|
- Read and understand all the bender manufacturers’ operating and safety instructions before operating their equipment.
- It is extremely important that the bender, its components and accessories are matched to the conduit type and size being bent because of the forces being applied. When using a power bender, it is important that pins are in the proper pin holes for the conduit size.
- Although the National Electric Code® allows up to 360 degrees between pulling points, using as few bends as possible, and none exceeding 90 degrees, will make wire pulling easier. The fewer total degrees between pulling points and the use of shallow bends combine to reduce the strain created by pulling wire. For multi-conductor control cable and communications cable, it is recommended that runs be limited to two 90 degree bends (a total of 180 degrees) per EIA / TIA-569 Commercial Building Standard for Telecommunications Pathways and Spaces.
- Before placing the conduit in the bender, accurately measure and mark the conduit with a thin line that goes completely around the conduit. This will ensure that the mark is visible if the conduit needs to be rotated.
- The minimum radius shall comply with NEC, Chapter 9, Table 2 and the measurement shall be made to the centerline of the bend. See EIA / TIA-569 Commercial Building Standard for Telecommunications Pathways and Splices for guidance on bend radius for conduit and tubing used with communication and optical fiber cables.
- Where hand benders do not have degree markings, degrees of bend shall be measured to the inner edge of the conduit (the surface that fits in the groove).
- Where it is necessary to compensate for spring back, slightly over-bend.
- When using a hand bender, choose a solid, flat surface. Pin the conduit firmly to the surface with steady foot pressure sufficient to keep the conduit and bender marks aligned and the conduit nestled in the groove throughout the full arc of the bend.
Bending steel RMC
NOTE: Benders recommended for a larger size range may be capable of bending some sizes below their primary range if so equipped.
Trade sizes 1/2, 3/4 and 1 can be bent with a hand-type bender. Trade sizes 1 1/4 and 1 1/2 require a power bender or a mechanical ratchet-type bender. Bend trade sizes 2 and larger on a power bender.
Do not put conduit ends in the hook or bending shoe of the bender because thread damage and end flattening will occur.
When an EMT bender is designated as suitable for bending rigid conduit, a bender shoe one trade size larger than the conduit to be bent is to be used. Using the EMT bender will result in a slightly larger radius.
A full shoe or universal bender is the preferred bending tool for IMC. Limit hand bending to trade sizes 1/2, 3/4, and 1. To make hand bending of trade size 1 easier, use a two position foot-pedal bender. This allows more weight to be applied for leverage.
Trade sizes 1 1/4 and 1 1/2 require a power bender or a mechanical ratchet-type bender. Trade sizes 2 and larger require a power bender.
NOTE: Benders recommended for a larger size range may be capable of bending some sizes below its primary range if so equipped.
Use a bender of the correct trade size designed for bending EMT. EMT trade sizes 1/2, 3/4 and 1 can be bent with hand benders because of the thinner wall. Use a mechanical ratchet-type bender for trade sizes 1 1/4 and 1 1/2. Use a power bender for trade sizes 2 and larger.
NOTE: Bending EMT in an oversized EMT bender will flatten the bend and possibly kink the tube.
When making a short radius bend, straightening stubs in concrete, or applying greater than normal stress to bend 1/2 or 3/4 EMT, place a mandrel into the EMT to support the wall. Any object that can be inserted to support the wall and is flexible enough to be bent and 11 is removable can be used. A spring, rope, or hose are typical items used. Use a lubricant to aid in extracting the mandrel.
Knocked-down EMT stubs which can be bent using a hand bender (1/2 through 1) can be straightened by placing the bender handle over the stub and pulling back to the desired position. If kinked, insert a drift-pin, working it back and forth while inserting; this should force the tube back to round.
To shift the position of a stub of a vertical run when the stub is slightly out of line, remove handle from bender and place bender head on the EMT with the step-end of bender down. Brace bender head with your foot and apply pressure against tube and pull. Over bend the stub slightly beyond the intended position to compensate for spring-back. Place handle back into bender and bend to desired vertical position.
When a stub or horizontal run is located close to the floor, remove concrete from around the EMT raceway. Put the bender in the stub with the step-end down, brace with your foot and bend.
NOTE: If step-end is not down, the bender could get wedged during the bending process.
To bend EMT coming out of a wall, remove handle and insert a close nipple. Thread a 90 degree pipe elbow onto the nipple and thread the handle into the elbow. The handle will parallel the bender center. This provides clearance to swing the handle down to make the bend.