Machining Operations and Machine Tools Review Questions

Question 1

What are the differences between rotational parts and prismatic parts in machining?

Answer 1

Rotational Parts

Cylindrical / disk shaped and are machined on a turning machine

Prismatic Parts

Blocked shaped or flat and are generally produced on a milling machine, shaper, or planer

Question 2

Distinguish between generating and forming when machining workpart geometries.

Answer 2

Generating

Geometry of the workpart is determined by the feed trajectory of the cutting tool. The path followed by the tool during its feed motion is imparted to the work surface in order to create the shape

Forming

Shape of the part is created by the geometry of the cutting tool. The cutting edge of the tool has the reverse of the shape to be produced on the part surface

Question 3

Give two examples of machining operations in which generating and forming are combined to create workpart geometry

Answer 3

• thread cutting on a lathe
• slotting on a milling machine

Question 4

Describe the turning process

Answer 4

Machine process in whic a single-point tool removes material from the surface of a rotating workpiece. Toll fed linearly in a direction parallel to the axis of rotation to generate a cylindrical geometru

Question 5

What is the difference between threading and tapping?

Answer 5

Threading performed on a turning machine and produces external threads

Tapping performd on a drilling machine and prdocues internal threads

Question 6

How does a boring operation differ from a turning operation?

Answer 6

Boring produces internal cylindrical shape from an existing hole

turning produces an external cylindrical shape

Question 7

What is meant by the designation 12 x 36 inch lathe?

Answer 7

Has a 12 inch swing (maximum work diameter that can be accomodated) and a 36 inch distance between centers (maximum work length that can be held between carriers)

Question 8

R16.8Name the various ways in which a workpart can be held in a lathe

Answer 8

• Between centers
• Chuck
• Collet
• Face plate

Question 9

What is the difference between a live center and a dead center, when these terms are used in the context of workholding in a lathe?

Answer 9

Center

Holds the workpiece at the tailstock end of the live

Live Center

Mounted in bearings and rotates with the work

Dead Center

Does no rotate, the work rotates about it

Question 10

What is a blind hole?

Answer 10

Blind Hole

Does not exit the work

Through Hole

Hole exits both sides of the work

Question 11

wHAT IS THE DISTINGUISHING FEATURE OF A RADIAL DRILL PRESS?

Answer 11

Large drill press designed to cut holes in large parts. Has a radial arm along which the drilling head can be moved and clamped.

Question 12

What is the difference between peripheral milling and face milling

Answer 12

Peripheral Milling

Axis of the tool is parallel to the surface being machined, and operation is performed by cutting edges on the outside periphery of the cutter

Face Milling

Axis of the cutter is perpendicular to the surface being milled, and machining is performed by cutting edges on both ends and outside periphery of the cutter

Question 13

Describe profile milling

Answer 13

Generally invovles the milling pf the outside periphery of a flat part

Question 14

What is pocket milling

Answer 14

Uses an end milling cutter to machine a shallow cavity (pocket) into a flat workpart

Question 15

Describe the difference between up milling and down milling?

Answer 15

Upmilling

Cutter speed direction is opposite of the feed direction

Downmilling

direction of cutter rotation is the same as the feed direction

Question 16

How does a universal milling machine differ from a conventional knee-and-column machine

Answer 16

Knee and column milling machine

basic machine tool for milling. Holds a single cutting tool. Main components are a column that supports the spindle and a knee that supports the worktable

Universal Milling Machine

Has a worktable that rotates about the vertical axis to present a part at a certain angle

Question 17

What is a machining center

Answer 17

A highly automated machine tool capable of performing multiple machining operations under a computer numerical control in one setup with minimal human attention

Question 18

What can a mill-turn center do that a conventional turning center cannot do?

Answer 18

CNC mill-turn center

Has general configuration of a turning center; can position cylindrical workpart at a specified angle so that a rotating cutting tool can machine features into the outside surface of the part

Question 19

How do shaping and planing differ

Answer 19

Shaping

Speed motion is accomplished by moving the cutting tool

Planing

Speed motion is accomplished ny moving the workpart

Question 20

What is the difference between internal broaching and external broaching

Answer 20

External Broaching

performed on outside surface of the work to create a certain cross-sectional shape on the surface

Internal Broaching

Accomplished on internal surface of the hole in the part

Question 21

What is the difference between a machining center and a turning center

Answer 21

Machining Centers

Can be applied to every surface of the workpiece

Turning Centers

Mainly used for cutting rotated workpieces

Question 22

How do a turning lathe differ from an engine lathe

Answer 22

Turret Lathe

has a toolholding turret in place of a tailstock; tools in the turret can be brought to work to perform multiple cutting operations on the work without needing to change tools

Engine Lathe

Requires manually replacing the tool for a specific machining operation

Question 23

Identify the 3 basic forms of sawing operations

Answer 23

• hacksawing
• bandsawing
• circular sawing

Question 24

Why do costs tend to increase when better surface finish is requried on a machined part

Answer 24

Additional operations such as grinding , lapping, or similar ginishing processes must be included in the manufacturing sequence

Question 25

What are the basic factors that affect surface finish in machining

Answer 25

• geometric factors
  
  • type of operation
  • feed
  • tool shape
• work material factors
  
  • built up edge effects
  • tearing of the work surface when machining ductile materials
• Vibration and tool factors
  
  • setup
  • work part rigidity
    
    • backlash in the feed mechanism
      *

Question 26

What are the parameters that have the greatest influence in determining the ideal surface roughness in a turning operation

Answer 26

• tool nose radius
• feed

Question 27

Name some of the steps that can be taken to reduce or eliminate vibrations in machining

Answer 27

• increase stiffness or damping in the setup
• operate at speeds away from the natural frequency of machine tool system
• reduce forces in machining by changing feed or depth and cutter design