Operates Machine-Tools — Tool and Die Maker (430A) Practice Questions

Free Operates Machine-Tools practice questions

1. 1.When cutting tool steel on a horizontal bandsaw, what coolant should be used?

   • A.No coolant
   • B.Soluble oil coolant to reduce heat and extend blade life✓
   • C.Water only
   • D.Air blast only

   Why: Soluble oil coolant lubricates the cut, reduces heat (preventing work hardening), extends blade life, and flushes chips. Dry cutting overheats and ruins both blade and material.

2. 2.When drilling a precision hole to be reamed, the drill should be:

   • A.Exactly the reamer size
   • B.0.010-0.015" undersize to leave material for the reamer✓
   • C.0.050" undersize
   • D.Oversize

   Why: Leave 0.010-0.015" (0.25-0.4mm) for the reamer to remove. Too little leaves no material for the reamer; too much overloads the reamer and produces a poor finish.

3. 3.Chatter marks on a turned surface are caused by:

   • A.Sharp cutting tool
   • B.Tool overhang too long, workpiece deflection, loose gibs, or improper speed/feed✓
   • C.Correct spindle speed
   • D.New chuck jaws

   Why: Chatter = vibration. Reduce tool overhang, support the workpiece (steady rest/follower rest), tighten gibs, adjust speed/feed, or change tool geometry to eliminate vibration.

4. 4.When boring on a lathe, the boring bar should be as large and short as possible to:

   • A.Look impressive
   • B.Maximize rigidity and minimize deflection/chatter✓
   • C.Increase speed
   • D.Reduce cost

   Why: A rigid boring bar resists cutting forces without deflecting. Deflection causes chatter, taper, and poor finish. Rule: bar length should not exceed 4× diameter for acceptable rigidity.

5. 5.A fly cutter on a milling machine is used for:

   • A.Drilling
   • B.Producing a flat surface with a single-point tool, typically for wide shallow facing cuts✓
   • C.Threading
   • D.Boring

   Why: Fly cutters use one insert/tool bit to face large flat surfaces. Cheaper than large face mills but slower (single cutting point). Good for tool and die surface finishing.

6. 6.Grinding burn on a hardened surface indicates:

   • A.Proper grinding
   • B.Excessive heat that has tempered (softened) the surface — a serious defect✓
   • C.Normal discoloration
   • D.Good finish

   Why: Burn marks mean surface temperature exceeded tempering temperature, softening the hardened steel. This creates a soft spot that wears prematurely. Re-harden and re-grind, or scrap the part.

7. 7.When grinding a flat die plate, how is parallelism ensured?

   • A.Eyeball it
   • B.Grind one side, flip the part, and grind the other side referencing the ground surface. Check with indicator.✓
   • C.Grind only one side
   • D.Use a file

   Why: Grind one face flat. Clean and place ground face down on the magnetic chuck. Grind the second face. Now both faces are parallel to each other. Verify with indicator across the part.

8. 8.In CNC wire EDM, what is the purpose of the guide dies?

   • A.Cut the wire
   • B.Support and position the wire electrode precisely above and below the workpiece✓
   • C.Hold the workpiece
   • D.Supply coolant

   Why: Upper and lower guide dies (diamond or sapphire) position the wire with micron accuracy. Worn guides cause poor accuracy and taper. They must be replaced at recommended intervals.

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