The short answer
Assess industrial machinery mechanics on four dimensions: precision practice (alignment and bearing fitting), root cause diagnosis rather than repeat replacement, discipline within planned shutdown windows, and composure when a line is stopped. Technical breadth matters less than these.
Precision practice
Alignment tolerances, bearing fits, belt tension and lubrication determine whether a machine runs for years or fails within months. This is where average and strong candidates separate most clearly.
Alignment questions
- “Which alignment method do you use, and to what tolerance?”
- “How do you check for soft foot, and why does it matter?”
- “How do you account for thermal growth on a hot running machine?”
- “What alignment tools have you worked with?”
Strong candidates mention laser alignment or dial indicators, specific tolerances, soft foot checks and thermal compensation. Answers about aligning “by eye” or “with a straight edge” indicate limited precision work — acceptable for some roles, not for critical rotating equipment.
Bearing questions
- “How do you fit a bearing, and why that method?”
- “What causes premature bearing failure in your experience?”
- “How do you determine the correct fit and clearance?”
- “How do you handle and store bearings before fitting?”
Root cause thinking
This is the single highest-value trait in production maintenance, because reactive maintenance generates more reactive maintenance.
Ask: “Tell me about a failure that kept recurring. What did you find, and what changed?”
| Answer pattern | What it tells you |
|---|---|
| Traced repeated bearing failure to misalignment or contamination and corrected the cause | Strong — thinks in systems |
| Changed a lubrication regime after analysing failure pattern | Strong — uses evidence |
| Describes replacing the same component repeatedly with no investigation | Reactive only |
| Cannot recall any recurring failure | Probe further — either limited exposure or limited reflection |
Working under production pressure
A stopped line creates pressure that changes how people work. Composure and method under that pressure is a distinct skill from technical knowledge.
- “The line is down and management is asking for an estimate. You do not know the cause yet. What do you say?”
- “How do you decide between a quick temporary fix and a proper repair?”
- “When would you stop and escalate rather than continuing?”
- “How do you avoid making the situation worse when you are being rushed?”
Shutdown discipline
Planned maintenance windows are fixed. Overrunning one converts a weekend shutdown into a Monday production loss, so preparation matters as much as execution.
- Has worked within defined shutdown windows
- Prepares parts, tools and procedures in advance
- Can estimate task duration realistically
- Understands the consequences of overrun
- Contributes to shutdown scope planning
- Documents what was actually done and what was deferred
Documentation and boundaries
Two often-overlooked areas that cause real problems when missing.
- Documentation: without maintenance history, recurring failures are never recognised as patterns. Ask what they record and why.
- Scope boundaries: mechanical and electrical work should not blur without proper qualification. Ask where they draw the line and when they hand over to an electrician.
A practical assessment you can actually run
For this profile a hands-on test is unusually informative, because precision practice is visible in a way that interview answers are not. A bearing replacement with alignment is the single most revealing task available to you.
The task
Give the candidate a pedestal bearing or a small drive assembly on a training rig, with the task of replacing the bearing and aligning the coupling to a stated tolerance. Allow 90 to 120 minutes. Provide the tools and the specification; do not provide the method.
What you will see
- Whether they isolate and secure before starting
- How the bearing is removed — puller or hammer tells you a great deal
- Whether they check the shaft and housing before fitting
- Fitting method: induction heating, press, or force through the rolling elements
- Whether cleanliness is maintained throughout
- Whether soft foot is checked before alignment
- Whether the final alignment is measured or assumed
- Whether they record what they did
Red flags in this profile
- Aligns “by eye” or with a straight edge. Acceptable for some rough applications, disqualifying for critical rotating equipment.
- Cannot name a tolerance. Precision work is defined by numbers; vagueness here means the numbers were never used.
- Blames component quality for repeat failures. Sometimes true, usually a sign that root cause was never investigated.
- Willing to work on electrical systems without qualification. A safety concern and a boundary problem.
- Estimates shutdown durations without asking about scope. Indicates limited experience of fixed maintenance windows.
- Treats documentation as someone else’s job. Without records, failure patterns stay invisible indefinitely.
Key takeaways
- Root cause thinking is the highest-value trait. Replacing the failed bearing is average; finding why it failed is not.
- Alignment answers are diagnostic. Laser alignment, soft foot checks and thermal growth indicate real precision practice; aligning by eye indicates its absence.
- Bearing fitting method reveals standards instantly. Driving a bearing on by striking the outer race damages it before the machine runs.
- Composure under stoppage pressure is a distinct skill. Good candidates commit to a diagnostic checkpoint rather than inventing an estimate.
- Define the electrical boundary explicitly. Ambiguity here creates both safety and expectation problems.
Assessing without a training rig
Not every plant has a spare assembly to hand for assessment purposes. Where that is the case, there are workable substitutes.
A walk of the production floor with the candidate, asking them to describe what they would check on a specific machine and why, reveals a surprising amount — familiarity with equipment types, safety instinct, whether they look at alignment and lubrication points unprompted.
Alternatively, present photographs of a failed component from your own records and ask what they think caused it. A candidate who works backwards from wear patterns to a root cause is showing you the trait that matters most in this role.
