Machining operations and tools

Question 1

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

Answer 1

r. Rotational parts are cylindrical or disk-shaped and are machined on a turning
machine (e.g., a lathe); prismatic parts are block-shaped or flat and are generally produced
on a milling machine, shaper, or planer.

Question 2

Distinguish between generating and forming when machining part geometries.

Answer 2

Generating refers to creating part geometry using the feed trajectory of the cutting
tool; examples include straight turning, taper turning, and profile milling. Forming involves
creating part geometry using the shape of the cutting tool; common examples include form
turning and drilling.

Question 3

Describe the turning process

Answer 3

Turning is a machining process in which a single-point tool removes material
from the surface of a rotating cylindrical work piece, the tool being fed in a direction
parallel to the axis of work rotation.

Question 4

What is the difference between threading and tapping?

Answer 4

A threading operation is performed on a turning machine and produces an
external thread, while tapping is normally performed on a drilling machine and produces an
internal thread.

Question 5

How does a boring operation differ from a turning operation?

Answer 5

Boring produces an internal cylindrical shape from an existing hole, while turning
produces an external cylindrical shape.

Question 6

What is meant by the designation 30 cm x 90 cm (12 in x 36 in) lathe?

Answer 6

A 30 cm x 90 cm (12 in x 36 in) lathe has a 30 cm (12 in) swing (maximum work diameter that can be accommodated) and a 90 cm (36 in) distance between centers (indicating the maximum work length that can be held between centers).

Question 7

Name the various ways in which a work part can be held in a lathe.

Answer 7

Methods of holding the work in a lathe include: (1) between centers

(2) chuck
(3) collet
(4) face plate

Question 8

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 8

A center holds the workpiece at the tailstock end of the lathe. A live center is
mounted in bearings and rotates with the work, while a dead center does not rotate - the
work rotates about it.

Question 9

How does a turret lathe differ from an engine lathe?

Answer 9

A turret lathe has a tool-holding turret in place of a tailstock; the tools in the turret
can be indexed to perform a sequence of different cutting operations on the work without the need to change tools as in operating a conventional engine lathe.

Question 10

What is a blind hole?

Answer 10

A blind hole does not exit the work; by comparison, a through hole exits the opposite side of the work part.

Question 11

What is the distinguishing feature of a radial drill press?

Answer 11

A radial drill has a long radial arm along which the drill head can be positioned to allow the drilling of large work parts. The radial arm can also be swiveled about the column to drill parts on either side of the worktable.

Question 12

What is the difference between peripheral milling and face milling?

Answer 12

In peripheral milling, the axis of the tool is parallel to the surface being machined, and the operation is performed by cutting edges on the outside periphery of the cutter. In face milling, the axis of the cutter is perpendicular to the surface being milled, and machining is performed by cutting edges on both the end and outside the periphery of the cutter.

Question 13

Describe profile milling.

Answer 13

Profile milling generally involves the milling of the outside periphery of a flat part.

Question 14

What is pocket milling?

Answer 14

Pocket milling uses an end milling cutter to machine a shallow cavity (a “pocket”) into a flat work part.

Question 15

Describe the difference between up milling and down milling

Answer 15

In up milling, the cutter speed direction is opposite the feed direction; in down
milling, the 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

The universal milling machine has a worktable that can be rotated about a vertical axis to present the part at any specified angle to the cutter spindle.

Question 17

What is a machining center?

Answer 17

A machining center is a CNC machine tool capable of performing multiple types of cutting operations involving rotating spindles (e.g., milling, drilling); the machine is typically equipped with automatic tool changing, pallet shuttles to speed work part changing, and automatic work part positioning.

Question 18

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

Answer 18

A machining center is generally confined to rotating spindle operations (e.g.,
milling, drilling); while a turning center performs turning type operations, generally with
single-point tools.

Question 19

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

Answer 19

A mill-turn center has the capacity to position a rotational work part at a specified angular location, permitting milling or drilling to be performed at a location on the periphery of the part.

Question 20

How do shaping and planing differ?

Answer 20

In shaping, the work is stationary during the cut, and the speed motion is performed by the cutting tool; whereas in planing, the cutting tool is stationary, and the work part is moved past the tool in the speed motion

Question 21

Broaching is performed using a rotating multi-tooth cutting tool: (a) true or (b) false?

Answer 21

(b) Broaching uses a multiple-tooth tool to take multiple cuts by moving the tool linearly relative to the work in the direction of the tool axis.

Question 22

What is the difference between internal broaching and external broaching?

Answer 22

Internal broaching is accomplished on the inside surface (hole) of a work part; while external broaching is performed on one of the outside surfaces of the part.

Question 23

Identify the three basic forms of sawing operation?

Answer 23

The three forms of sawing are: (1) hacksawing, (2) bandsawing, and (3) circular sawing.

Question 24

What does the term thread chasing refer to?

Answer 24

The term thread chasing is applied to production thread-making operations that utilize self-opening dies which are designed with an automatic device that opens the cutting teeth at the end of the cut.

Question 25

What is the name of the most common process for cutting internal threads?

Answer 25

Tapping.

Question 26

Gear hobbing is basically which of the following types of machining operations , (a) grinding, (b) milling, or (c) shaping?

Answer 26

b). Gear hobbing is basically a milling operation, but the cutter, called a hob, is much more complex than a conventional form milling cutter. In addition, special milling machines (called hobbing machines) are required to accomplish the relative speed and feedmotions between the cutter and the gear blank.