AWS Tools & Equipment Operation 3 — Questions and Answers
Question 1: What is the purpose of the ground clamp in an arc welding circuit?
- To hold the workpiece in position during welding
- To complete the electrical circuit by connecting the workpiece to the power source's work terminal (Correct answer)
- To prevent the electrode from sticking
- To measure voltage at the arc
Correct answer: To complete the electrical circuit by connecting the workpiece to the power source's work terminal
The work clamp (ground clamp) provides the return path for welding current from the workpiece back to the power source.
Question 2: Which lens shade number is generally recommended for GMAW (MIG) welding at 150–250 amperes?
- Shade 5
- Shade 10 (Correct answer)
- Shade 14
- Shade 3
Correct answer: Shade 10
AWS Z49.1 recommends shade 10 for GMAW at 150–250 amps to protect the eyes from arc radiation at that amperage range.
Question 3: What happens if MIG welding contact tips become worn or oversized?
- Shielding gas flow increases automatically
- The wire develops poor electrical contact, causing erratic arc starts and inconsistent bead quality (Correct answer)
- Wire feed speed increases
- The polarity reverses
Correct answer: The wire develops poor electrical contact, causing erratic arc starts and inconsistent bead quality
An enlarged contact tip bore creates electrical resistance variations, leading to arc instability and poor fusion.
Question 4: On a TIG welding machine, the high-frequency (HF) start function is used to:
- Increase penetration on thick aluminum
- Initiate the arc without touching the tungsten electrode to the base metal (Correct answer)
- Clean the oxide layer on steel
- Control post-flow shielding gas timing
Correct answer: Initiate the arc without touching the tungsten electrode to the base metal
HF start ionizes the shielding gas gap, allowing arc ignition without contaminating the tungsten by touching the workpiece.
Question 5: What does the term 'open circuit voltage' (OCV) refer to on a welding machine?
- The voltage present at the output terminals when the arc is burning
- The voltage at the output terminals when no arc is established and no current is flowing (Correct answer)
- The input line voltage from the utility supply
- The voltage drop across the welding cable
Correct answer: The voltage at the output terminals when no arc is established and no current is flowing
OCV is the no-load output voltage; it must be high enough to establish the arc but drops significantly once welding current flows.
Question 6: A wire brush used to clean a weld bead after SMAW should be made of:
- Brass bristles to avoid sparks
- Carbon steel bristles compatible with the base metal being welded (Correct answer)
- Nylon bristles to avoid scratching
- Aluminum to prevent contamination of steel
Correct answer: Carbon steel bristles compatible with the base metal being welded
Steel wire brushes on carbon steel remove slag and spatter without introducing foreign metals that could cause contamination.
Question 7: The amperage output of a welding machine should be checked with:
- A standard multimeter on AC voltage setting
- A calibrated clamp-on ammeter placed around the welding cable (Correct answer)
- A resistance meter across the electrode holder jaws
- An infrared thermometer on the transformer housing
Correct answer: A calibrated clamp-on ammeter placed around the welding cable
A clamp-on ammeter measures DC or AC current without breaking the circuit, giving an accurate reading of actual welding amperage.
AWS Tools & Equipment Operation 3
What is the purpose of the ground clamp in an arc welding circuit?