17 Surface Grinding & Drill Press Practice Questions & Answers

1. 1. Two aluminum oxide surface grinding wheels are identical except that one is marked 46 grit and the other 150 grit. Which statement about the two wheels is correct?

   • A.The 150 grit wheel has the finer grains and will leave the better surface finish✓ Answer
   • B.The 46 grit wheel has the finer grains, because a lower grit number always means smaller abrasive particles
   • C.The grit number states how widely the grains are spaced, so the 150 wheel is the more open of the two wheels
   • D.The grit number states the strength of the bond, so the 150 wheel is the harder-grade wheel of the two

   The grain (grit) number comes from the mesh screen used to size the abrasive, so it runs inversely: the higher the number, the smaller the particle and the finer the finish. Grain spacing is the separate structure number and bond strength is the grade letter, so neither of those is what the grit number reports.

   Source: ANSI B74.13 grinding wheel marking system, grain-size element; NIMS Machining Level I Grinding, Wheel Characteristics & Grinding Wheel Codes (Duty 2.7b)Report a problem with this question

2. 2. In a standard grinding wheel marking such as A60J8V, what does the letter J identify?

   • A.The hardness of the abrasive grains themselves, rated on the same scale that sets the abrasive type letter
   • B.The grade — how tightly the bond grips the abrasive grains✓ Answer
   • C.The structure, meaning how widely the individual grains are spaced within the wheel
   • D.The bond material that holds the wheel together, such as vitrified, resinoid or shellac

   In the marking sequence the third element is the grade letter, and grade describes the strength with which the bond retains the grains — a "hard" wheel simply holds worn grains longer. Grades run A-H soft, I-P medium and Q-Z hard, so J is a medium wheel; the abrasive type is the leading A, the structure is the 8 and the bond is the V.

   Source: ANSI B74.13 marking sequence (abrasive, grain size, grade, structure, bond); NIMS Machining Level I Grinding worked marking example A60J8VBEReport a problem with this question

3. 3. A brazed tungsten carbide lathe tool must be resharpened on a grinding wheel. Which abrasive should be used?

   • A.Aluminum oxide, the general-purpose abrasive used for most tool grinding
   • B.CBN (borazon), the standard abrasive for cemented carbide tooling
   • C.Diamond, because only diamond and silicon carbide are hard enough to cut tungsten carbide✓ Answer
   • D.Ceramic aluminum oxide, which is formulated for high-tensile cutting tool materials

   Tungsten carbide is harder than aluminum oxide in any of its forms, so an aluminum oxide wheel merely rubs and burns it; only diamond and silicon carbide (green silicon carbide is the cheaper substitute) will actually cut carbide. CBN grinds hardened ferrous alloys and cobalt/nickel superalloys, not cemented carbide.

   Source: NIMS Machining Level I Grinding — Grinding Carbide & Carbide Tooling (Duty 2.7b)Report a problem with this question

4. 4. A surface grinding wheel still runs concentric with the spindle, but its face is shiny, it burns the work and it skips. What does the wheel need?

   • A.Trueing, because trueing is the operation that restores the cutting action while dressing only removes spindle runout
   • B.A slower spindle speed, since a shiny wheel face is caused by surface speed alone
   • C.Nothing; a glazed face is normal and it will clear itself after several passes
   • D.Dressing — it breaks away the dull grains and exposes sharp new cutting edges✓ Answer

   Dressing and trueing are different jobs: trueing makes the wheel face concentric and running true to the spindle, while dressing restores sharp cutting grains and the correct face. A glazed wheel is already running true, so the cure is dressing, which also removes a loaded face.

   Source: NIMS Machining Level I Grinding — Dressing a Grinding Wheel (trueing vs. dressing, Duty 2.7b)Report a problem with this question

5. 5. While surface grinding brass and aluminum parts, the wheel face keeps packing full of the ground metal. Which wheel change corrects the problem?

   • A.A wheel with a more open structure, giving more chip clearance between the grains✓ Answer
   • B.A wheel with a much denser structure, so the closely packed grains cannot trap chips
   • C.A harder grade, so the grains are held long enough to keep cutting the soft metal instead of smearing it
   • D.A finer grit size, because smaller grains cut smaller chips

   Loading is soft, gummy material becoming embedded in the pores of the wheel, so the wheel-selection parameter that matters for copper, brass and other non-ferrous metals is structure. A wider grain spacing (open structure) gives the chips room to clear instead of welding into the face.

   Source: NIMS Machining Level I Grinding — wheel structure selection for non-ferrous material (Duty 2.7b)Report a problem with this question

6. 6. Hardened tool steel is being surface ground at normal wheel speed and the parts are burning while the wheel face glazes over. Which wheel should replace it?

   • A.A harder grade wheel, since hard work material calls for an equally hard wheel
   • B.A softer grade wheel, because hard material takes a soft wheel: worn grains release early and keep exposing fresh cutting edges✓ Answer
   • C.The same wheel run with the coolant shut off, so the wheel face stays dry and free cutting
   • D.The same wheel with a much heavier down feed to force the dull grains through the work

   The standard inversion in grinding is that hard material takes a soft wheel and soft material takes a hard wheel. A grade that is too hard holds the grains after they dull, which is exactly what produces glazing, burning and the skipping that leaves chatter marks; a softer grade lets the bond release worn grains so the wheel keeps cutting cool.

   Source: NIMS Machining Level I Grinding — Process Improvement/Troubleshooting: hard material requires a soft-grade wheel (Duty 2.7b)Report a problem with this question

7. 7. What is the accepted way to check a vitrified grinding wheel for cracks before it is mounted?

   • A.Examine the whole wheel closely under good light; a crack large enough to matter is always visible
   • B.Mount it and run it at full speed for one minute behind the guard; a cracked wheel will fail during that run
   • C.Suspend the wheel on a pin and tap it lightly with a non-metallic handle: a clear ring means it is sound, a dull thud means it is cracked✓ Answer
   • D.Tap the rim in several places with a steel hammer and listen for a change in tone

   The ring test works because a sound vitrified wheel is an unbroken elastic body that rings when struck, while a crack damps the vibration into a dead thud. Visual inspection alone misses internal and hairline cracks, a steel implement can start a crack, and spinning a suspect wheel is not a test but an accident.

   Source: OSHA 29 CFR 1910.215(d)(1) and ANSI B7.1 ring test; NIMS Machining Level I Duty 2.7a Grinding Wheel SafetyReport a problem with this question

8. 8. A .375 in HSS twist drill is to run at a cutting speed of 90 SFPM. Using RPM = 3.82 x SFPM / D, what spindle speed should be set?

   • A.960 RPM
   • B.344 RPM
   • C.240 RPM
   • D.917 RPM✓ Answer

   Multiply first, then divide: 3.82 x 90 = 343.8, and 343.8 / .375 = 917 RPM. The 960 RPM answer comes from the shop approximation RPM = 4 x SFPM / D, which is deliberately rougher; when the stem specifies the 3.82 constant, the decimal-diameter formula is the one that must be used.

   Source: Machinery's Handbook speed formula RPM = 3.82 x SFPM / D; NIMS Drill Press Level I — Drilling Speeds, Feeds & Basic Math (Duty 2.8)Report a problem with this question

9. 9. A .500 in hole was drilled at a cutting speed of 100 SFPM and will now be reamed to size with a .500 in reamer. Reaming speed is about half of drilling speed. Using RPM = 3.82 x SFPM / D, what RPM should the reamer run at?

   • A.382 RPM✓ Answer
   • B.764 RPM
   • C.191 RPM
   • D.1,528 RPM

   Halve the cutting speed first: 100 SFPM / 2 = 50 SFPM, then 3.82 x 50 = 191, and 191 / .500 = 382 RPM. The companion rule is that reaming feed goes the other way — roughly two to three times the drilling feed — and candidates who invert one of the two rules end up at 764 RPM, the full drilling speed.

   Source: NIMS Drill Press Level I — Reaming Procedures (reaming speed about one half of drilling speed); Machinery's Handbook RPM formulaReport a problem with this question

10. 10. A print shows five equally spaced holes in a straight row. The distance from the center of the first hole to the center of the fifth hole is 4 11/16 in. What is the center-to-center spacing between adjacent holes?

    • A.15/16 in
    • B.1 11/64 in✓ Answer
    • C.1 3/16 in
    • D.2 11/32 in

    Five holes create only four spaces between the first and the fifth, so 4 11/16 in (4.6875) divided by 4 gives 1.171875 in, which is 1 11/64 in. Dividing by the hole count instead of the space count yields 15/16 in and is the classic off-by-one error on this type of item.

    Source: NIMS Drill Press Level I — Basic Math for hole layout (n holes give n-1 spaces), Duty 2.8Report a problem with this question

11. 11. As a twist drill is about to break through the far side of a workpiece, what should the operator do with feed pressure?

    • A.Increase it, to push the drill cleanly through the last of the material
    • B.Increase it briefly and then release the feed handle so the drill free-wheels through
    • C.Decrease it, because the thin ring of material left can no longer support the lips, and full feed lets the drill grab, tear a burr or snap off✓ Answer
    • D.Hold it constant, since feed pressure has no effect once the point reaches the far surface

    At breakthrough the remaining web of material is too thin to resist the thrust, so the lips dig in and the drill is pulled into the work. Easing the feed keeps the drill from grabbing, protects the drill from breakage and leaves a cleaner hole mouth needing less deburring.

    Source: NIMS Drill Press Level I — Basic Drilling Procedures, reduce feed at breakthrough (Duty 2.8)Report a problem with this question

12. 12. An HSS twist drill is producing blue chips while drilling steel. What is the most likely cause?

    • A.The feed is too light, so the drill is rubbing instead of cutting and needs more feed
    • B.The web has been thinned too far, which lets the chisel edge overheat and discolor every chip it makes
    • C.The point angle is too small for steel, so the margins are dragging in the hole
    • D.The spindle RPM is too high, so reduce the cutting speed✓ Answer

    Chip color is a direct read-out of the heat generated at the cutting edge, and cutting speed is the variable that generates that heat fastest. Blue chips from a high speed steel drill mean the surface speed is above what the tool can shed, and continuing will draw the temper out of the drill point.

    Source: NIMS Drill Press Level I — Process Improvement / Drilling Troubleshooting (chip color vs. cutting speed)Report a problem with this question

13. 13. A reamed hole is flared out at the top but correct in size farther down — a bellmouthed hole. What is the cause?

    • A.The reamer or the spindle is out of alignment with the hole✓ Answer
    • B.The reamer is oversize across its chamfer and cutting edges, which enlarges the hole uniformly from top to bottom
    • C.Too little stock was left for reaming, so the reamer burnished the hole instead of cutting it
    • D.The reamer was turned backward while it was being withdrawn from the hole

    A misaligned reamer or spindle swings the entry end of the reamer in a small orbit as it starts, so it cuts a cone at the mouth before the body of the reamer is guided by the hole itself. An oversize reamer would enlarge the entire hole rather than just the top, and turning a reamer backward dulls it but does not flare the mouth.

    Source: NIMS Drill Press Level I — Reaming Procedures (bellmouth caused by misalignment), Duty 2.8Report a problem with this question

14. 14. A rough cast surface must be machined into a small flat pad around an existing hole so that a bolt head and washer seat evenly. What is this operation called?

    • A.Counterboring
    • B.Spotfacing✓ Answer
    • C.Countersinking
    • D.Center drilling

    A spotface is a shallow machined flat that creates an even bearing surface on a rough or uneven casting. A counterbore is a deeper flat-bottomed enlargement that recesses a socket head cap screw, a countersink is a conical enlargement (82 degrees for standard commercial flat head screws) and a center drill spots a location and cuts the 60 degree bearing for lathe centers.

    Source: NIMS Drill Press Level I — Countersinking, Counterboring, Spotfacing & Center Drilling definitions (Duty 2.8)Report a problem with this question

15. 15. Which statement about the web of a twist drill is TRUE?

    • A.It is the same width along the entire length of the flutes
    • B.It is the narrow cylindrical strip of the land that sizes and guides the drill in the hole
    • C.It thickens toward the shank, so a drill shortened by repeated regrinding usually needs its web thinned to keep feed pressure reasonable✓ Answer
    • D.It carries the chips up out of the hole and lets cutting fluid down to the point

    The web is the column of metal between the flutes that forms the chisel edge at the dead center, and it is tapered thicker toward the shank to give the drill strength. Because the chisel edge extrudes rather than cuts, a thicker web demands more thrust, which is why a shortened drill is web thinned; the sizing strip is the margin and chip removal is the job of the flutes.

    Source: NIMS Drill Press Level I — Twist Drill Nomenclature & Sizing (web thickness, web thinning), Duty 2.8Report a problem with this question

16. 16. Which of these drill press practices is UNSAFE?

    • A.Positioning the vise so that the workpiece would swing into the column if the drill grabs
    • B.Brushing hot chips off the table with a chip brush after the spindle has stopped turning
    • C.Taking the chuck key out of the chuck as soon as the drill is tightened and storing it away from the machine
    • D.Positioning the vise so that the workpiece would swing toward the operator if the drill grabs✓ Answer

    A drill that grabs at breakthrough can spin the vise and the work like a club, so the setup is always oriented to let that rotation stop against the column rather than sweep through the operator's position. Chips are removed with a brush and only with the spindle stopped, and the chuck key never stays in the chuck.

    Source: NIMS Drill Press Level I — Safety Practices (workholding orientation relative to the column; chuck key and chip removal), Duty 2.8Report a problem with this question

17. 17. Which drill press component carries the rotating spindle and slides up and down to feed the drill into the work?

    • A.The quill✓ Answer
    • B.The column
    • C.The table-locking lever
    • D.The base

    The quill is a hollow sleeve that houses the spindle bearings and is driven down by the feed handle through a rack and pinion, so the spindle turns while the quill itself only translates. The column supports the head and carries the table, the table-locking lever clamps the table at the chosen height, and the base anchors the machine.

    Source: NIMS Drill Press Level I — Drill Press Components (quill and spindle function), Duty 2.8Report 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 →