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2-2 Threading Conduit

Once rigid-steel conduit is cut, it must be threaded for use with threaded couplings, locknuts, and bushings. To thread conduit, use a pipe-cutting die with a standard pipe thread of 3/4-inch taper per foot. This die cuts a deeper thread on the end of the conduit and then tapers the cut at the rear or shoulder of the thread. This is just the opposite of a running thread on a bolt.

The dies used for threading smaller sizes of conduit are usually hand-driven (Figure 2-6). The handle may be solidly attached to the die, or the die assembly may be a ratchet-type. When using larger sizes or installing large amounts of conduit that require considerable threading, a motor-driven, pipe-threading machine is recommended.

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Figure 2-6. Nonadjustable ratchet and dies

The most common rigid-steel conduit threader is a nonadjustable ratchet and dies, which come in sizes to fit conduit from 1/2 inch to 2 inches (Figure 2-6).

Before threading the conduit, inspect the dies to see that they are sharp and free from nicks and wear. Next, insert the conduit into the vise, place the guide end of the pipe threader on the conduit, and push the threading dies against the conduit with the heel of your hand (Figure 2-7).

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Figure 2-7. Threading conduit

With pressure against the threader, take three or four short, clockwise strokes downward to start the threads. Continue the threading with clockwise strokes, mixed with a reverse stroke every now and then, until two or three threads extend beyond the die. To reverse the threader, pull the ratchet lock out and turn it a half turn. The reverse turns keep the threads and dies clean and free of bits of metal. Cutting oil applied during the threading helps the cutting process by reducing friction. To remove the threader, release the ratchet lock and turn the die by hand counterclockwise. Removal of the die also cleans the threads.

It is important that the right amount of threads be cut for the job. In other words, a full thread must be cut so that the ends of the conduit come together in the coupling (Figure 2-8).

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Figure 2-8. Threaded coupling

Full threads are also necessary for the conduit to make a firm seat in the end threads of the hub. Cutting threads until two or three threads extend beyond the die usually gives you a full thread. However, if too many threads are cut, the conduit will fit too loosely in the coupling or against the hub.

Power threaders come in the following two types: stationary threaders built for use in the shop and portable threaders built for use in the field. Both types are driven by electric motors that have adjustable chucks and dies for use on different sizes of conduit. Portable threaders normally handle conduit up to 2 inches. Shop threaders may be built to handle conduit up to 6 inches. Consult the manufacturer's operating instructions before using these power tools.

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David L. Heiserman, Editor

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All Rights Reserved

Revised: June 06, 2015