18 Shop Safety & Machine Maintenance Practice Questions & Answers

1. 1. A machinist wants to clear coolant and fine chips out of a milling fixture with the shop air hose. Which practice meets the OSHA requirement for cleaning with compressed air?

   • A.Reduce the nozzle pressure to under 30 psi and use effective chip guarding plus eye and face protection.✓ Answer
   • B.Use full line pressure but hold the nozzle well back from the fixture so the chips lose speed before they reach anyone.
   • C.Use full line pressure and turn the head away while blowing, since the air is aimed down into the fixture.
   • D.Reduce the nozzle pressure to under 30 psi, then finish by blowing the chips off the sleeves and forearms.

   Compressed air may be used for cleaning only when the dead-end pressure at the nozzle stays under 30 psi AND effective chip guarding plus personal protective equipment are used; the pressure limit by itself still lets a chip be driven into an eye, which is why the partial answers fail. Air is never used on skin or clothing, because a stream at that pressure can drive chips and air through the skin.

   Source: OSHA 29 CFR 1910.242(b) — compressed air used for cleaningReport a problem with this question

2. 2. At the end of a shift a machinist has a pile of shop wipes soaked in way oil plus the absorbent used on a coolant spill. What is the correct way to handle them?

   • A.Spread them flat on the bench overnight so the oil dries off, then drop them in the regular trash in the morning.
   • B.Put them in an approved metal container with a self-closing lid that is emptied on a set schedule, and handle the used absorbent as regulated waste.✓ Answer
   • C.Throw them into the chip hopper with the steel turnings so the whole load leaves the shop with the scrap.
   • D.Seal them in a plastic bag under the parts washer until enough have collected to be worth a disposal pickup.

   Oil on cloth oxidizes and gives off heat; a wadded pile insulates that heat so the temperature climbs to the ignition point with no spark at all, which is spontaneous combustion. A closed metal container limits the oxygen and confines any fire, and oil-soaked absorbent behaves exactly the same way, so it goes in the same container and is disposed of as hazardous waste rather than in general trash.

   Source: OSHA 29 CFR 1910.106(e)(9)(iii) and NFPA 30 — oily waste in approved covered metal containersReport a problem with this question

3. 3. A long stringy steel chip is wrapping around the tool on a running engine lathe. What should the operator do?

   • A.Catch the chip with a folded shop rag and pull it away while the spindle keeps turning.
   • B.Flick it off with the point of a scriber while the spindle keeps turning, so the cut is not interrupted.
   • C.Stop the spindle and let it come to a complete rest, then pull the chip clear with a chip hook or brush before restarting the cut.✓ Answer
   • D.Pull it off by hand wearing a leather glove, since the leather protects against the sharp edge.

   A chip still attached to rotating work is being pulled by the machine, so a rag, a glove or a bare hand that touches it is wound in faster than anyone can let go. Stopping the spindle removes the energy that causes the entanglement, and a chip hook or brush keeps the hand out of the cutting zone away from chips that are razor sharp and hot.

   Source: NIMS Machining Level I Duty 6.1 basic shop safety; OSHA 29 CFR 1910.212(a)(1) point of operationReport a problem with this question

4. 4. Why are gloves forbidden when running a drill press or an engine lathe, even though they protect the hands from sharp chips?

   • A.Glove leather soaks up cutting fluid and holds coolant mist against the skin, which brings on dermatitis.
   • B.Gloves deaden the operator's feel, so the drill is fed too hard and the part is more likely to spin in the vise.
   • C.Gloves insulate the operator from the machine frame, so static charge builds up and can discharge into the control.
   • D.A glove that brushes the rotating drill or workpiece is wound up instantly and drags the hand in with it.✓ Answer

   The hazard is entanglement: once glove material starts to wrap on a turning spindle, drill or workpiece, no amount of grip strength or reaction time can stop the hand from being pulled into the point of operation. It is the same reason loose sleeves, neckties, jewelry and unrestrained long hair are barred at rotating machinery; gloves are worn to handle rough stock and chips away from the machine and come off before it is started.

   Source: OSHA 29 CFR 1910.212(a)(3)(ii) point of operation; NIMS Machining Level I Duty 6.1Report a problem with this question

5. 5. Two machinists must move a 90 lb milling vise from a bench onto a mill table. What is the correct lifting procedure?

   • A.Squat with the back straight, hold the vise against the body, and lift with the legs.✓ Answer
   • B.Bend at the waist with the legs straight and keep the vise out at arm's length so it clears the knees as it comes up.
   • C.Lift it fast in one motion from the waist so the load is carried for the shortest possible time.
   • D.Rest the vise on the hip and twist at the waist to swing it over onto the table.

   Lifting with the legs while the spine stays in a neutral position and the load is held close to the body keeps the lever arm short, so the compressive force on the lower back stays far lower than in a stooped or arm's-length lift. Twisting under load is a leading cause of disc injury, so the feet are repositioned instead, and a load beyond safe capacity is moved with help or a hoist.

   Source: NIOSH lifting guidance; NIMS Machining Level I Duty 6.1 material handlingReport a problem with this question

6. 6. A pile of magnesium turnings under a bandsaw catches fire. What is the correct response?

   • A.Play the water hose on it at once, since a large volume of water will cool the metal below its ignition temperature.
   • B.Smother it with a Class D dry powder extinguisher and alert others to clear the area.✓ Answer
   • C.Use the ABC dry chemical extinguisher on the aisle post, since ABC is rated for ordinary combustibles, flammable liquids and metals alike.
   • D.Flood it with coolant from the machine sump so the fluid seals the burning turnings off from the air.

   Burning magnesium is hot enough to break water down into hydrogen and oxygen, so water — or water-based coolant — produces a steam explosion that scatters burning metal instead of putting the fire out. Class D dry powder is the only correct agent because it forms a crust that excludes air from the metal; ABC dry chemical is rated for Class A, B and C fires and carries no Class D rating.

   Source: NFPA 10 and OSHA 29 CFR 1910.157(d) — Class D extinguishers for combustible metal firesReport a problem with this question

7. 7. A machinist is slinging a die block down from the top rack of the material storage area with the overhead crane. Besides safety glasses and safety shoes, what PPE is required?

   • A.A face shield, because the sling can whip toward the face as it takes up the load.
   • B.A respirator, because material stored overhead collects dust that is stirred up as it is moved.
   • C.A hard hat, because stock or the load itself can fall from the rack or the crane.✓ Answer
   • D.Hearing protection, because the crane hoist is the loudest equipment in the bay.

   Head protection is required wherever there is a risk of objects falling from above, and both an overhead rack and a suspended crane load create exactly that hazard. PPE is selected from the hazard actually present — a face shield answers flying chips at a grinder, not falling steel — and it remains the last line of defense, so inspecting the rigging and never standing under a suspended load come first.

   Source: OSHA 29 CFR 1910.135 head protection; 29 CFR 1910.132 PPE hazard assessmentReport a problem with this question

8. 8. The chip shield on a vertical mill partly blocks the operator's view of the cut. What is the correct action?

   • A.Swing the guard out of the way for this setup only and stand off to one side, since one operator working alone controls the whole exposure.
   • B.Take the guard off and wear a face shield over the safety glasses instead, since the shield covers the same hazard.
   • C.Loosen the guard so it can be pushed aside quickly during the cut and tighten it again when the job is done.
   • D.Leave the guard in place and stop the spindle whenever a close look at the cut is needed.✓ Answer

   A guard is an engineering control: it works whether or not the operator is paying attention, which is why the machine guarding rule forbids removing, bypassing or loosening it and requires the point of operation and power transmission parts to stay covered. Personal protective equipment sits at the bottom of the hierarchy of controls and stops flying chips but not contact with a turning cutter, and measuring, adjusting or inspecting the work is always done with the spindle stopped.

   Source: OSHA 29 CFR 1910.212(a)(1)–(a)(3) — machine guarding and point of operationReport a problem with this question

9. 9. A machinist has locked and tagged the disconnect on a surface grinder before changing the wheel. What must still be done before the work starts?

   • A.Relieve any stored energy, then try to start the machine at its normal controls and return them to off.✓ Answer
   • B.Post a second tag at the operator's station warning others that the grinder is out of service.
   • C.Have another machinist stand at the disconnect and watch it while the wheel is changed.
   • D.Write the lockout up on the machine history form and tell the supervisor the grinder is down.

   Lockout/tagout is not complete until the zero-energy state is verified, because a lock only proves that nobody can re-energize the source that was locked — it does not prove the right disconnect was opened or that stored energy is gone. Attempting a normal start tests both at once and reveals residual spring, hydraulic, pneumatic, capacitor or gravity energy; the controls are returned to off afterward, and only the worker who applied a lock may remove it.

   Source: OSHA 29 CFR 1910.147(d)(6) — verification of isolationReport a problem with this question

10. 10. The safety data sheet for a parts-washer solvent lists a flash point. What does that number tell the machinist?

    • A.The leanest mixture of solvent vapor and air that will still carry a flame away from an ignition source.
    • B.The lowest temperature at which the liquid gives off enough vapor to form an ignitable mixture at its surface.✓ Answer
    • C.The airborne concentration a worker can be exposed to day after day without expected adverse health effects.
    • D.The temperature at which the liquid ignites on its own, with no spark or open flame present.

    Flash point is a temperature that describes the liquid's vapor: below it, the liquid simply is not giving off enough vapor to be ignited, which is why it governs how a solvent is stored, warmed and used near ignition sources. The distractors are the terms most often swapped with it — the lower explosive limit is a vapor concentration, the threshold limit value is an exposure level, and autoignition temperature needs no ignition source; flash point appears in Section 9 of the sixteen-section SDS.

    Source: OSHA Hazard Communication 29 CFR 1910.1200 (GHS SDS Section 9); NFPA 30 definition of flash pointReport a problem with this question

11. 11. A drum of cutting oil carries an HMIS label. Which color bar will never be found on it?

    • A.White, which carries the PPE letter code.
    • B.Orange, which rates physical hazard on the current HMIS revision.
    • C.Green, which does not appear anywhere on the label.✓ Answer
    • D.Blue, which rates the health hazard.

    An HMIS label uses blue for health, red for flammability, white for the PPE letter code, and a fourth bar that is yellow for reactivity on HMIS II or orange for physical hazard on HMIS III; green is an ANSI safety-sign colour for first aid and safe conditions and is never an HMIS bar. Both HMIS and the NFPA 704 diamond (blue, red, yellow, white) rate hazards 0 for minimal to 4 for severe, and an asterisk beside the HMIS health rating flags a chronic health hazard.

    Source: HMIS III label format (American Coatings Association); NFPA 704 color schemeReport a problem with this question

12. 12. At daily start-up an operator must lubricate a manual knee mill. Which practice is correct?

    • A.Pump grease onto the ways and gibs, since grease stays put longer than oil and will not drip on the table.
    • B.Wipe cutting oil onto the ways and lead screws, since it is already at the machine and will not attract chips.
    • C.Run coolant from the sump over the ways at the end of the shift, since the mix already carries a rust inhibitor.
    • D.Send way oil through the one-shot lubricator, and grease only the Zerk fittings the builder specifies.✓ Answer

    Way lube is a specific oil with tackifier and anti-stick-slip additives, and the one-shot lubricator meters it to the sliding surfaces where a hydrodynamic film has to form; grease pumped on the ways would fill the oil grooves, trap chips and lift the table off its film. A grease gun belongs only on Zerk fittings the builder specifies, while coolant washes lubricant away and promotes rust and cutting oil lacks the film strength for slideways.

    Source: NIMS Machining Level I Duty 5.2 — machine lubrication (way lube vs. grease fittings)Report a problem with this question

13. 13. A three-jaw chuck is mounted on a lathe that checked out true last week, and now the chuck body and every part gripped in it run out badly. What is the most likely cause?

    • A.Chips and grit left on the spindle nose and on the back face of the chuck, holding the chuck off its seat.✓ Answer
    • B.The chuck jaws were put back in the wrong order, so they do not close concentrically.
    • C.The headstock oil level dropped below the sight glass over the past week.
    • D.The tailstock was left offset from an earlier taper job and is pushing the work off center.

    A chuck locates on machined mating surfaces, so a chip only a few thousandths thick trapped between the spindle nose and the chuck's mounting face tilts the entire chuck, and that tilt is multiplied into large runout out at the workpiece. The spindle nose, taper and mounting face are wiped clean and deburred before a chuck goes on; jaw order affects only how the jaws grip, and neither oil level nor tailstock setting can move a mounted chuck body off center.

    Source: NIMS Machining Level I Duty 5.2 — cleaning workholding mounting surfacesReport a problem with this question

14. 14. Shop coolant has started to smell sour on Monday mornings and finished parts are showing light rust. What should the operator do first?

    • A.Add a little way oil to the sump so the mix carries more rust protection.
    • B.Take a refractometer reading and correct the concentration to spec.✓ Answer
    • C.Top the sump off with plain water to dilute whatever is causing the odor.
    • D.Turn the coolant pump up so the fluid keeps moving through the machine.

    A sour smell plus rust is the classic signature of a lean mix: the emulsion's rust inhibitor and biocide fall with the concentration, and bacteria multiply in fluid that sits still over a weekend. A refractometer measures the concentration before anything is added, which is why it is the first step; adding plain water makes the mix leaner still, and tramp oil such as way oil floats on top, seals the sump from air and feeds the bacteria.

    Source: NIMS MMS competency 'Refractometer Readings' — coolant concentration control (Duty 5.2)Report a problem with this question

15. 15. Where does a machinist find the specified lubricant type and the preventive-maintenance schedule for one particular machine?

    • A.The part print, which carries the job's material, finish and tolerance requirements.
    • B.The process plan, which lists the operations, tooling and cutting data for the job in the machine.
    • C.The machine builder's manual and that machine's preventive-maintenance schedule.✓ Answer
    • D.Machinery's Handbook, the shop reference for machining data, fits and thread standards.

    Lubricant type, fill capacity and service frequency are machine-specific engineering data published by the builder and carried into the shop's preventive-maintenance schedule, so the manual is the only document that can answer the question. Prints, process plans and reference handbooks describe the part, the job or general machining data rather than a machine's service needs, and any condition beyond the operator's authority is reported to the supervisor and recorded on the machine history form.

    Source: NIMS Machining Level I Duty 5.2 — locating maintenance procedures (manufacturer's manual)Report a problem with this question

16. 16. A machinist picks up a mill file to break the edges on a plate and finds that the file has no handle. What should be done?

    • A.Wrap the tang in a shop rag for a grip and keep the other hand on the file point.
    • B.Use it only for light draw filing, where both hands press on the file body instead of the tang.
    • C.Hold the file by the body with both hands and keep the palm well clear of the bare tang.
    • D.Fit a properly seated handle on the tang before the file is used at all.✓ Answer

    The tang is a hardened, pointed spike, and if the file catches in the work or the workpiece shifts, that spike is driven straight back into the palm or wrist — the most common filing injury in a machine shop. A rag can slip and still puts the hand on the tang, so a fitted handle is the only acceptable fix; the same care applies to keeping files off each other in storage, cleaning them with a file card, and never using one as a pry bar because hardened files shatter.

    Source: NIMS Machining Level I Duties 5.1/5.3 — hand tool safety: never use a file without a handleReport a problem with this question

17. 17. Which cutting fluid is the best choice for hand tapping a 1/2-13 thread in low-carbon steel?

    • A.A sulfur-based cutting oil, which holds a film at the very low cutting speed of tapping.✓ Answer
    • B.Kerosene, thin enough to reach the flutes and flush the chips out of the hole.
    • C.A jet of compressed air, to clear chips from the hole and keep the tap cool.
    • D.Water-soluble coolant at normal machining concentration, which pulls heat out of the tap fastest.

    Tapping happens at almost no surface speed under extreme pressure with the chip trapped in the hole, so the limiting factor is lubrication rather than cooling. Sulfur additives react with the steel to form a low-shear film that keeps the chip from pressure-welding to the tap, which prevents galling, torn threads and broken taps; sulfurized oil is kept off copper alloys because it stains them, and compressed air is not a lubricant at all.

    Source: NIMS Machining Level I Duty 5.3 — cutting fluid selection for tapping steelReport a problem with this question

18. 18. A machinist offhand-grinds a 1/2 in. high-speed-steel drill and the holes it drills come out several thousandths oversize. What is the most likely cause?

    • A.The point was ground to a 118-degree included angle instead of a sharper point.
    • B.The two cutting lips were left unequal in length or angle.✓ Answer
    • C.The web was thinned at the chisel edge before the lips were ground.
    • D.The drill was dipped in water often during grinding instead of being left to cool in air.

    If one lip is longer or ground at a different angle than the other, that lip takes a heavier cut and pushes the drill sideways, so the point orbits and cuts a hole larger than the drill while one corner wears rapidly. A correct general-purpose grind has both lips the same length and at the same angle to the axis with proper lip relief; web thinning at the chisel edge is normal practice that reduces thrust, and dipping high-speed steel frequently is what keeps the grind from overheating and drawing the temper.

    Source: NIMS Machining Level I Duty 5.3 — tooling maintenance: drill point geometry and offhand grindingReport a problem with this question

Practice questions based on NIMS/ANSI 101-2001, Duties and Standards for Machining Skills Level I, and the published content of the NIMS Machining Level I theory exams, together with standard precision-machining practice. NIMS is a mark of the National Institute for Metalworking Skills; this site is not affiliated with or endorsed by NIMS. Machining Level I is a set of separate credentials, and most of them also require a hands-on performance test that this bank does not cover. The NIMS theory exams are open-reference, but questions here never depend on recalling a handbook table value, a citation number or a machine rating — always work from the print in front of you, your employer's written procedures, and the machine's own documentation, and confirm current requirements before testing. About the NIMS machining credentials →