Cutting, Threading, Bending, and Joining of Pipes and Fittings
Cutting, threading, bending, and joining
This domain tests hands-on technique and defect recognition. The exam expects square cuts, correct thread form, controlled bends, and joints that pass a pressure test.
Core rules
- Cut square with a wheel cutter or fine-tooth saw; ream the inside and file the outside burr. A burr reduces flow and can damage a seal.
- For threads, use the correct die size and thread standard, apply cutting oil, start the die squarely, and reverse to clear chips. A properly cut thread leaves two to three threads exposed when the fitting is hand-tight.
- Bend within the minimum radius; use a bending spring or a proper bender for copper, and follow the manufacturer's temperature and time for heat-fused PPR. A kinked bend is a reject.
- Solvent joints: clean, prime if required, apply cement to both surfaces, assemble with a quarter turn, hold, and allow full cure before pressure.
- Soldered copper: clean to bright metal, flux sparingly, heat the fitting, and feed solder until a capillary line appears; do not overheat.
- Threaded joints: apply PTFE tape clockwise or approved sealant, leaving the first thread clear.
Worked example
A 1/2-inch GI line needs a threaded connection. The pipe is cut square, reamed, and clamped. The candidate applies cutting oil, starts the 1/2-inch die, cuts a thread about the fitting's engagement length, backs off, cleans chips, and checks by hand-tightening the fitting. Two threads remain visible; the joint is then tightened with a wrench, not over-tightened. The reasoning: thread length and square start control leakage and cracking.
Traps
Dry threading, cross-threading, failing to ream, over-bending to a kink, disturbing a solvent joint before cure, and using too much flux all cause failures that appear in testing.