Tools, Equipment, and Shop Maintenance
What the exam tests
This domain tests whether you can keep a refinish shop's air, guns, booth, and hand tools within specification. Expect questions on compressed-air quality, spray-gun components, filter and booth maintenance, and the effect of worn equipment on finish quality.
Core rules
- Compressed air is a tool, not a utility. Drain the receiver daily, service the separator and coalescing filter, and use a desiccant or refrigerant dryer where the product sheet requires dry air. Oil, water, and particulate cause fish-eye and poor adhesion.
- Match the fluid tip, needle, and air cap to the material and the gun. A tip that is too small forces high pressure and poor atomization; a worn needle set causes spitting and an uneven pattern.
- Set inlet pressure with the gun triggered and flowing, not static. Use the manufacturer's gauge point and confirm with a pattern test on paper or a test panel.
- Keep booth filters clean and record manometer readings. A rising reading means falling airflow, even if the fan sounds normal.
- Clean guns promptly with the correct solvent, including the air cap, fluid tip, needle, and passages, but do not soak the whole gun or submerge seals in aggressive solvent.
- Maintain sanders, blocks, and mixing scales. A scale that is out of calibration ruins mixing ratios; a worn DA pad leaves pigtails.
Worked example
A gun produces a split or heavy-center pattern after a rebuild. The technician first checks the air cap for damage and clogs, confirms the correct cap for the tip, then checks inlet pressure with the trigger pulled. If the pattern is still heavy in the center, the fluid tip or needle may be worn or mismatched. Increasing pressure to hide the defect is the wrong fix because it increases overspray and dry spray.
Traps that cost marks
- Raising pressure to compensate for a worn tip.
- Judging pressure with the gun static.
- Soaking an entire gun in solvent and damaging seals.
- Ignoring a rising booth manometer or a full filter.