Sinan Sever 030070127 _ 1st week definitions

Dimensional Tolerance

previous definition(better): This is defined as the permissible or acceptable variation in the dimensions ( height, width, depth, diameter, and angles) of a part. The root of the word “tolerance” is the Latin tolerare, meaning “to endure” or “put up with.” Tolerances are unavoidable, because it is virtually impossible ( and unnecessary) to manufacture two parts that have precisely the same dimensions.

(Kalpakjian S., Schmid S.R.,Manufacturing Engineering and Technology, 5th Edition, pg.1102)

new definition: The term dimensional tolerance refers to the permissable variation from a specified dimension in a product. the degree of accuracy which may be expected will depend on whether the product is hot or cold rolled, the type of rolling mill equipment used, unavoidable operating contingincies, the specified size or edge condition, and in some cases steel composition.

(Blusecope Steel Limited Product Dimensional Tolerance Handbook, 4th ed. 2003, pg.4)

Experimental Prototype

previous definition(better): Additional early prototypes are common in situations where the product embodies a new concept or technology. These early prototypes are sometimes called experimental or engineering prototypes. They usually do not look like the final product, and many of the parts of the prototype are not designed with the intention of eventually being produced in quantity.
(Kalpakjian S., Schmid S.R.,Manufacturing Engineering and Technology, 5th Edition, pg.262)

new definition: An experimental prototype is the type of prototype that is closest to the classical concept of prototype ("first of its kind"). It is experimental in the sense that it is built to try to determine whether the planned system will be adequate and acceptable when finished. Experimental prototypes can be used as requirements specification.

(Floyd, Christiane (1984): A Systematic Look at Prototyping. In: Budde, R., Kuhlenkamp, K., Mathiassen, Lars and Zullighoven, H. (eds.). "Approaches to Prototyping". Springer Verlag pp. 13)

High-Speed Steel

previous definition: First introduced in 1900 by Taylor and White , high speed steel is superior to tool steel in that it retains it's cutting ability at temperatures up to 1100F.exhibiting good 'red hardness'.Compared with tool steel, it can operate at about double the cutting speed with equal life, resulting High-speed steels, often abbreviated HSS.
High-speed steels contain significant amounts of W,Mo,Co,V,and Cr besides Fe and C.W,Mo,Cr, and Co in the ferrite as a solid solution provide strengthening of the matrix beyond the tempering temperature,thus increasing the hot hardness.Vanadium(V),along with W,Mo,and Cr, improves hardness and wear resistance.Extensive solid solutioning of the matrix also ensures good harden ability of these steels.

(MATERIALS AND PROCESSES IN MANUFACTURING 7th edition E.PAUL DEGARMO P.551)

new definition(better): High speed steel (HSS or HS) is a subset of tool steels, commonly used in tool bits and cutting tools. It is often used in power saw blades and drill bits. It is superior to the older high carbon steel tools used extensively through the 1940s in that it can withstand higher temperatures without losing its temper (hardness). This property allows HSS to cut faster than high carbon steel, hence the name high speed steel. At room temperature, in their generally recommended heat treatment, HSS grades generally display high hardness (above HRC60) and a high abrasion resistance (generally linked to tungsten content often used in HSS) compared to common carbon and tool steels.

(Roberts, George, et al., "Tool Steels", 5th edition, ASM International, 1998)

Geometric Tolerancing

previous definition:  Geometric tolerancing specifies the tolerance of geometric characteristics. Basic Geometric characteristics as defined by ANSI Y14.5M 1982 standard include Straightness, Flatness, Roundness, Cylindricity, Profile, Parallelism, Perpendicularity, Angularity, Concentricity, Runout and True Position.
To specify the geometric tolerances, reference features - planes, lines or suraces - can be established.
(Computer Aided Manufacturing, T.Chang, R.A Wysk, H.Wang, Second Edition, Prentice Hall International Series, 1998. Page: 25)

new definition(better): Geometric dimensioning and tolerancing (GD&T) is a system for defining and communicating engineering tolerances. It uses a symbolic language on engineering drawings and computer-generated three-dimensional solid models for explicitly describing nominal geometry and its allowable variation. It tells the manufacturing staff and machines what degree of accuracy and precision is needed on each facet of the part.

(Dimensioning and Tolerancing, ASME y14.5-2009. NY: American Society of Mechanical Engineers. 2009.)

Atmosphere Furnaces

previous definition: Atmosphere furnaces are characterized by their use of a protective atmosphere to surround the workload during heating and cooling. The most common furnace atmosphere, however, is air. Often times,nothing more is needed. When an air atmosphere is used, such as in a low temperature tempering operation, the final condition of the material’s surface (or skin) is not considered important. Furnace atmospheres play a vital role in the success of the heat treating process. It is important to understand why we use them and what the best atmosphere for a specific application is. There are many different types of atmospheres being used, and it is important to understand how a particular atmosphere is chosen as well as its advantages and disadvantages and to learn how to control them safely.The purpose of a furnace atmosphere varies with the desired end result of the heat treating process. The atmospheres used in the heat treating industry have one of two common purposes:

1. To protect the material being processed from surface reactions, i.e., to be chemically inert(or protective)

2. To allow the surface of the material being processed to change, i.e., to be chemically active(or reactive)

Some atmospheres such as argon and helium are often associated with vacuum furnaces and are used at partial pressure (pressure below atmospheric pressure). Others, such as sulfur dioxide are used for very special applications 

(Geng H., Manufacturing Engineering Handbook, p. 18.51)

new definition(better): The most common atmospheres used in controlled-atmosphere furnace brazing operations are classified as exothermic, endothermic, dissociated ammonia, and industrial gas-based (generated or delivered). Typically these atmosphere furnaces will be of a multi-chamber design, with each chamber (pre-heat, high heat, cooling) separated by either gas curtains at the entry and exit points to protect against air/oxygen infiltration. A schematic representation of a typical atmosphere furnace is shown below.

(Introduction to Furnace Brazing, Diran Apelian et al, pg22)