Machinist Program: Lathe Operations

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Questions and Answers

What is the objective of the parallel turning operation?

To turn a taper on the lathe

To verify that the lathe turns parallel to the axis (correct)

To perform center drilling and reaming operations

To demonstrate the use of taps and dies

What should you do if the diameter is smaller at the tailstock during parallel turning?

Adjust the cutting tool to reduce the diameter

Move the tailstock away from you by half the difference (correct)

Take another trial cut

Move the tailstock towards you by half the difference

What is the purpose of the parallel test bar?

To measure the diameter of the workpiece

To check if the dial moves as you move the carriage along the workpiece (correct)

To mount the cutting tool

To adjust the tailstock

In what direction should the tailstock be moved if the work is large at the tailstock end?

Towards the operator Signup and view all the answers

How many trial cuts should be taken to verify parallel turning accuracy?

Two trial cuts Signup and view all the answers

What is the purpose of adjusting the tailstock?

To make the workpiece parallel to the axis Signup and view all the answers

What happens if the diameter is the same on both ends during parallel turning?

The tailstock is aligned Signup and view all the answers

What is the purpose of the dial indicator on the cross-slide during parallel test bar operation?

To check if the dial moves as you move the carriage along the workpiece Signup and view all the answers

When performing heavy facing operations, what should you do with the carriage?

Always lock the carriage Signup and view all the answers

What is the purpose of a tool height centering device?

To adjust the tool height Signup and view all the answers

What is the recommended feed rate for roughing cuts?

0.010” to 0.030” per revolution Signup and view all the answers

How much should you leave for each finishing cut?

2x tool nose radius Signup and view all the answers

What is the purpose of taking a trial cut in diameter verification?

To compensate for the measured diameter Signup and view all the answers

What is the effect of backlash on a lathe?

It creates clearance between the cross-slide screw and nut Signup and view all the answers

What does each graduation on the cross-feed dial typically represent?

0.001 inches or 0.02 mm Signup and view all the answers

When adjusting the tool height, how much should you adjust towards you if the workpiece is 0.004 larger at the tailstock?

0.002 Signup and view all the answers

What is the purpose of the thread center gauge in threading operations?

To align the threading tool to the work piece axis Signup and view all the answers

What is the recommended RPM when using HSS tooling for threading on a lathe?

About 1/4 the normal turning speed Signup and view all the answers

What is the formula used to calculate the in feed for half angle threading?

In Feed = 0.750 X Pitch Signup and view all the answers

What is the purpose of using a modified die head?

To thread an external thread Signup and view all the answers

What is the purpose of the compound rest in half angle threading?

To set the angle of the threading tool Signup and view all the answers

Why is center height critical in threading operations?

Because it affects the accuracy of tapered threads Signup and view all the answers

What is the formula used to calculate the thread depth in plunge cutting?

Depth = 0.6495 X Pitch Signup and view all the answers

What is the purpose of using the spindle face to guide a die?

To keep the die parallel to the axis of the machine Signup and view all the answers

What is a common cause of center drill breakage?

Centers not aligned properly Signup and view all the answers

What should be the color of the chip when using HSS drills?

Dicoloured Signup and view all the answers

What is the purpose of peck drilling?

To break long chips Signup and view all the answers

What is the recommended material allowance for reaming under 1/2 inches?

1/64th Signup and view all the answers

What is the recommended speed for grooving operations?

½ of normal turning speed Signup and view all the answers

What is a critical consideration when parting a workpiece off?

Never parting a workpiece off when it is between centers Signup and view all the answers

What is the recommended RPM for knurling operations?

200 RPM or less Signup and view all the answers

What is the purpose of reversing the workpiece rotation at the end of the knurl?

To return to the start position Signup and view all the answers

What is the formula to calculate TO when the whole shaft is tapered?

(D - d) Signup and view all the answers

What is the purpose of bluing a taper for fit?

To check the accuracy of the taper Signup and view all the answers

What is the typical diameter reduction during Emory polishing?

.001" or less Signup and view all the answers

What is the recommended feed rate for a tool post grinder?

1/2 the wheel width per revolution Signup and view all the answers

Why is it important to ensure the lathe and the grinding wheel are turning in opposite directions during tool post grinding?

To prevent the work piece from becoming out of round Signup and view all the answers

What is the recommended removal rate for a tool post grinder?

.001" to .002" per rotation of the work Signup and view all the answers

What is the recommended speed for a tool post grinder?

200 RPM Signup and view all the answers

Why is regular maintenance important for an engine lathe?

To ensure the accuracy and precision of the lathe Signup and view all the answers

Study Notes

Lathe Operations

Objective: Set up cutting tools to perform parallel turning and boring operations
Importance of verifying parallel turning accuracy: ensure the lathe turns parallel to the axis
Methods to verify parallel turning accuracy:
- Take two trial cuts (or one long cut) and check the diameter at both ends
- Use a parallel test bar: mount between centers, mount a dial indicator on the cross-slide, and check if the dial moves as you move the carriage along the workpiece
Adjusting the tailstock:
- Move the upper casting away from or towards the operator
- If the workpiece is larger at the tailstock end, move the tailstock towards the operator
- If the workpiece is smaller at the tailstock end, move the tailstock away from the operator

Cutting Accuracy

Tool height adjustments:
- Always lock the carriage when performing heavy facing operations
- Verify tool height using methods:
  - Turn the tool towards the tailstock bearing center and adjust the height to match the center point
  - Use a spring steel rule
Tool height centering device:
- Use to verify tool height
Roughing and finishing:
- Roughing: feed rate should be as high as the machine and tooling can handle (0.010” to 0.030” per revolution)
- Finishing: feed rate depends on the finish required on the part
Accurate diameters:
- Rough to 0.100 larger than the finished diameter
- Reduce feed for the required finish
- Take a 0.050” cut and measure the workpiece
- Take the final cut, compensating for the measured diameter and final diameter

Drilling and Reaming

Drilling:
- When using HSS drills, the chip should be discolored
- Break long chips by performing peck drilling
- Pull the drill out of the hole fully after 4 times its diameter
Reaming:
- Machine reaming: use 1/2 the speed, 2 X the feed
- Material allowance: under 1/2 inches, leave 1/64th; over 1/2 inches, leave 1/32nd

Grooving, Parting, Knurling, Threading Operations

Grooving:
- Tool set as short as possible but still cut the groove required
- Speed: ½ of normal turning speed
- Use power feed with a goal to get the chip to curl and pop out of the groove
- Use plenty of cutting oil or coolant
Parting:
- Set appropriate tool overhang
- Never part a workpiece off when it is between centers
Knurling:
- Select the coarseness of the knurl
- Clamp the knurling tool in the tool post securely and at 90 degrees to the surface
- Run the lathe at 200 RPM or less
- Set the feed rate to the fastest that the manual lathe will go
- Put a significant pressure on the tool against the workpiece
- Motion the tool back and forth on the workpiece, then engage the feed
Threading:
- Threading setup and pitch verification:
  - Use a thread center gauge to align the threading tool to the workpiece axis
  - Use a screw thread pitch gauge to verify the correct pitch is being cut
- Methods of threading on a lathe:
  - Half-angle threading: use the compound rest set at 29.5 degrees
  - Plunge cutting: use the cross-slide, thread depth is calculated using the formula Depth = 0.6495 X Pitch

Tapping and Die Cutting Operations

Tapping in the lathe:
- Use the spindle face to guide a die so it remains parallel to the axis of the machine
- Use a modified die head to thread an external thread
Taper calculations – tail stock method:
- TO = (D - d) / 2 (if the whole shaft is tapered)
- TO = (D - d) X OL / 2 (if part of the shaft is parallel)

Finishing Operations

Polishing in the lathe:
- Hand polishing: use finer grit emery cloth, never hold emery with one hand, usually held to 0.001” or less diameter reduction
- Belt sanding attachment: use to polish the workpiece
Filing on the lathe:
- Filing tips: always hold the file handle with the left hand, never file more than 0.001 inches, use a lathe file or single cut file
Tool post grinders:
- Tool post grinding hints: removal is 0.001 to 0.002 per rotation of the work, ensure the lathe and grinding wheel are turning in opposite directions, speed: 200 RPM, feed: set to ½ the wheel width per revolution

Lathe Maintenance

Importance of lathe maintenance: the engine lathe is a precision machine tool and must be treated with great care.

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Description

This quiz covers the setup and operation of lathe machines, including parallel turning, boring, drilling, and other lathe operations. It is designed for shop training and Machinist Programs.