418 Final

What is a transfer die in sheet metalworking?

In transfer die stamping, a strip of metal is fed into the first station of a mechanical transport system, where the blank for the component is cut from the strip. The blank is the transferred mechanically through various stations until a finish part is produced

What is the difference between internal broaching and external broaching?

Internal broaching occurs on the inside of a hole or surface. While External broaching occurs on the outside of a hole or surface.

What is martensite?

Martensite is a unique phase (of the time-temperature-transformation curve of steels) consisting of an iron-carbon solution whose composition is the same as the austenite from which it was derived.

What is pearlite?

Mixture of ferrite and carbide. Forms this parallel plates.

What is the difference between natural aging and artificial aging in precipitation hardening?

Natural aging-room temp aging artificial aging-aging at an elected temp

How does nitriding work?

Nitriding is a treatment in which nitrogen is diffused into surface of certain alloy steel parts to produce a thin hard casing without quenching.

What is the difference between a notching operation and a seminotching operation?

Notching involves cutting out a portion of metal from the side of the sheet or strip while seminotcing removes a portion of metal from the interior of the sheet.

What is a turret press in sheet metalworking?

Press that moves in circular rotation.

Define drawing in the context of sheet metalworking.

Sheet metal forming to make cup-shaped, box-shaped, or other complex-curved, concave parts.

Define tool life as the term applies too machining.

amount of time a tool can cut and provide the needed quality.

Is the hardness of cemented carbides higher of lower than the hardness of high-speed steel?

cemented carbides-very hard High-speed steel- Not so hard

Identify the mechanisms by which cutting tools wear during machining.

diffusion, abrasion, plastic deformation, adhesion, chemical reaction.

What is a machine tool?

machine that powers & moves tool relative to a work piece.

The stresses and strains in metal forming are of which type, elastic or plastic?

plastic

Why is a six-spindle bar machine more productive than a single-spindle bar machine?

six-spindle- six parts at a time vs single-spindle-1 part at a time(need 6 machines to match six-spindle)

What is spinning in sheet metalworking?

spinning is the forming of an axis-symmetric part over a rotating mandrel. Force is delivered by a tool with a rounded end or a roller.

Identify some of the reasons why machining is commercially and technologically important.

· A variety of work materials can be machined · Variety of part shapes and special geometric features possible o Screw threads o Accurate round holes o Very straight edges and surfaces · Good dimensional accuracy and surface finish

Describe the forging process.

When a work piece is pressed between two dies so die shape is imported on work piece.

Describe the wire drawing process.

Wire drawing is a metal working process used to reduce the cross section of a wire by pulling it through a series of dies. This process is a type of forging, and can be done at either hot or cold temperatures.

Identify the selective surface-hardening methods.

1. Flame hardening 2. electrobeam 3.laser 4.high frequency resistance heating 5. inductive hardening

What are some of the advantages of warm working relative to cold working?

1. Less force involved 2. more intricate shapes are possible 3. no need for annealing

Why is friction generally undesirable in metal forming operations?

1. Restricts metal flow 2. it increases forces needed 3. it increases tool wear

Identify the three major categories of sheet metalworking operations.

1. cutting 2.bending 3. drawing

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

A live center is mounted in bearing and rotates with the work. While a dead center does not rotate, the work rotates around it.

What is the distinguishing feature of a radial drill press?

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 arm can also be swiveled about the column to work on either side of the work table.

Identify some of the common compounds that form the thin coating on the surface of coated carbide inserts.

Aluminum oxide Tin Nitride Tin carbide

What is the effect of carbon content on the machinability of steel?

An increase in carbon content will lead to a decrease of machinability of steel.

Why is friction in metal forming different from friction encountered in most mechanical systems such as gear trains, shafts in bearings, and other components involving relative motions between surfaces?

Because the friction in most metal forming processes is undesirable.

. How does a built-up edge affect surface finish in a turning operation?

Built-up edge will decrease the quality of the surface finish in a turning operation.

Is the elastic modulus of cemented carbides higher or lower than the hardness of high-speed steel?

Cemented carbides have a high elastic modulus (600*103 MPa), but have a toughness lower than that of high-speed steel.

What is the chip load in a milling operation?

Chip thickness per tooth

What is the type of deformation by which a chip is formed in metal machining?

Chips are formed from shear deformation.

Why is it difficult to deliver cutting fluid to the point of a conventional twist drill during a drilling operation?

Chips coming up flutes

In blanking of a circular sheet-metal part, is the clearance applied to the punch diameter of the die diameter?

Clearance is applied to punch diameter

What are some of the advantages of cold working relative to warm and hot working?

Cold working advantages: Better accuracy, closer tolerances, better surface finish, strain hardening increases strength and hardness, grain flow during deformation can cause desirable directional properties in product, no heating of work required.

What is the definition of a cermet?

Composite of ceramic & metal

Identify the two forces that can be measured in orthogonal cutting.

Cutting force Thrust force

Why can diamond cutting tools not be used to machine steel and other ferrous metals?

Diamond cutting tools can't be used to machine ferrous materials due the chemical reaction that takes place between them. This reaction results in severe wear of the tool, including oxidation, graphitization, and chipping.

What is explosive forming in sheet metalworking?

Explosive forming is the use of explosive charge to form sheet metal into a die cavity.(Used for large parts, typical of aerospace industry)

Describe the extrusion process.

Extrusion is a process used to create objects of a fixed cross section. A material is pushed through a die of the desired cross section. The extrusion process can be done with the material hot or cold.

In form milling of gear teeth, each gear tooth is milled individually by a form-milling cutter whose cutting edges have the shape of the gear tooth, true or false?

False, cutter look like space between the teeth.

Broaching is performed using rotating multi-tooth, true or false.

False, tool is pushed past or through part.

What are the factors on which the selection of feed in a machining operation should be based?

Feed depends on tooling (harder tool materials require lower feeds) and roughing or finishing. In roughing, limits on feed are imposed by forces, rigidity and power. While finishing, select feed to achieve desired finish.

What is a hemming operation in sheet metalworking?

Folding sheet metal to create a 180 degree bend

In which category is a broaching operation classified, generating or forming?

Forming

In which category is taper turning classified, generating or forming?

Forming

What are the two types of structural frame used in stamping presses?

Gap frame: configuration of the letter C and often referred to as a C-frame Straight-sided frame: box-like construction for higher tonnage.

Gear hobbing is basically which of the following types of machining operations: grinding, milling, or shaping.

Gear hobbing is a special type of milling machine.

Distinguish between generating and forming when machining part geometries.

Generating- part geometry is determined by the feed trajectory of cutting tool Forming- part geometry is created by the shape of the cutting tool

Identify three desirable properties of a cutting-tool material.

Hardness- resistance to wear toughness- does not fracture heat resistance- does not become ductile at low temps

What is the difference between full annealing and normalizing?

Heat material to austerity temp and air cool. Coarse pearlite. Same process with faster cooling. Fine pearlite.

What are the two main problems that cutting fluids are designed to address?

Heat-coolant-water based Friction-Lubricant-oil based

What are the benefits of increasing the shear plane angle in machining?

Higher shear force

Dry machining is being considered by machine shops because of certain problem inherent in the use of cutting fluids. What are those problems associated with the use of cutting fluids?

Problems associated with cutting fluids are contamination, disposal, and filtration.

When a punch and die are mounted in a press, is the punch attached to the ram or the bolster plate of the press?

Punch is attached to the ram.

What is the purpose of a tapping operation?

Putting threads in a hole.

Name the machining operation that is sometimes used after a drilling operation to achieve tighter tolerance on the hole diameter and improve surface finish?

Reaming

Explain the difference between roughing and finishing operations in machining.

Roughing- removes large amounts of material from starting work part. (High feeds and depths, low speeds) Finishing- completes part geometry (Final dimensions, tolerance, and finish. Low feeds and depths, high cutting speeds)

What are the two basic categories of cutting tools in matching? Give at least one example of matching operation that use each tooling type.

Single point tools- lathe multi point tools- drilling

What does the term soaking mean?

Soaking is when a furnace is held at a constant temperature, a metal is placed into the furnace to rearrange the internal structure of metal. Soaking temperature vary for different types of metals.

Why is a spade drill preferable to a twist drill for a large diameter holes such as 100mm (4.0 in)?

Spade drills are preferable for larger diameter holes because they can drill larger holes in shorter period of time.

What distinguishes material removal processes from other manufacturing processes?

Start is large part, remove material & end with a finished part.

What are the two main categories of cutting fluid according to function?

The two main functions of cutting fluid is: to reduce heat generation at shear and friction zones(coolants), and friction at tool-chip and tool-work interfaces(lubricants).

For what kinds of cutting tools is high-speed steel especially suited?

Tools with complex geometries.