18.1 What are the differences between rotational parts and prismatic parts in machining?
Answer. 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.
18.2 Distinguish between generating and forming when machining work part geometries.
Answer. Generating refers to the creation of work geometry due to the feed trajectory of the cutting tool; examples include straight turning, taper turning, and profile milling. Forming involves the creation of work geometry due to the shape of the cutting tool; common examples include form turning and drilling.
18.3 Give two examples of machining operations in which generating and forming are combined to create work part geometry.
Answer. The two examples given in the text are thread cutting on a lathe and slot milling.
18.4 Describe the turning process.
Answer. Turning is a machining process in which a single-point tool removes material from the surface of a rotating cylindrical workpiece, the tool being fed in a direction parallel to the axis of work rotation.
18.5 What is the difference between threading and tapping?
Answer. 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.
18.6 How does a boring operation differ from a turning operation?
Answer. Boring produces an internal cylindrical shape from an existing hole, while turning produces an external cylindrical shape.
18.7 What is meant by the designation 12 x 36 inch lathe?
Answer. A 12 x 36 lathe has a 12 inch swing (maximum work diameter that can be accommodated) and a 36 inch distance between centers (indicating the maximum work length that can be held between centers).
18.8 Name the various ways in which a work part can be held in a lathe.
Answer. Methods of holding the work in a lathe include: (1) between centers, (2) chuck, (3) collet, and (4) face plate.
18.9 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. 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.
18.10 How does a turret lathe differ from an engine lathe?
Answer. A turret lathe has a toolholding turret in place of a tailstock; the tools in the turret can be brought to work to perform multiple cutting operations on the work without the need to change tools as in operating a conventional engine lathe.
18.11 What is a blind hole?
Answer. A blind hole does not exit the work; by comparison, a through hole exits the opposite side of the work part.
18.12 What is the distinguishing feature of a radial drill press?
Answer. 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.
18.13 What is the difference between peripheral milling and face milling?
Answer. In peripheral milling, cutting is accomplished by the peripheral teeth of the milling cutter and the tool axis is parallel to the work surface; in face milling, cutting is accomplished by the flat face of the cutter whose axis is perpendicular to the work surface.
18.14 Describe profile milling.
Answer. Profile milling generally involves the milling of the outside periphery of a flat part.
18.15 What is pocket milling?
Answer. Pocket milling uses an end milling cutter to machine a shallow cavity (pocket) into a flat work part.
18.16 Describe the difference between up milling and down milling.
Answer. 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.
18.17 How does a universal milling machine differ from a conventional knee and column machine?
Answer. 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.
18.18 What is a machining center?
Answer. 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.
18.19 What is the difference between a machining center and a turning center?
Answer. 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.
18.20 What can a mill turn center do that a conventional turning center cannot do?
Answer. The 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.
18.21 How do shaping and planing differ?
Answer. 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.
18.22 What is the difference between internal broaching and external broaching?
Answer. 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.
18.23 Identify the three basic forms of sawing operation?
Answer. The three forms of sawing are: (1) hacksawing, (2) bandsawing, and (3) circular sawing.