Assignment # 02-tool Design

1) What is meant by locating? The term locating, as use in the language of the tool designer, to the dimensional and positional relationship between the work piece and the cutting tool used on the machine. The various forces acting upon the work piece during a machining operation necessitate a means of clamping it in position after it has been correctly located. 2) What is the major factor that determines how a work piece will be located? The major factor in determining how a work piece will be located. Examination of the typical work piece from the metal industries shows that the configuration is determined by a combination of flat, circular and irregular surfaces. Each of the three preceding surfaces type may be rough or finished. The tool designer studies the work piece care fully before deciding which surfaces are best suited for locating. 3) What is an irregular surface? Irregular surface are neither flat nor circular, they may or may not be geometrically true. For example, a parabolic or elliptical surface would be considered an irregular surface. A surface of work piece that may vary dimensionally from time to time would also be an irregular surface. 4) What is meant by complete location? Complete location has been accomplished by use of three points in (or parallel with) the reference plane, two points in a second plane and one point in a third plane. The locating points should be planed as far a part as possible to minimize the effect of inaccuracies in the work piece and locators. This separation also provides greater support because the locators are never the outer extremities of the work piece. 5) What is the basic reference for circular surface? The basic reference is the flat plane of the machine-tool table surface. The flat plane of the work piece parallel to the reference plane, it is necessary to locate the axis of the circular work piece. 6) What are the basic rules for applying clamping forces? Once a work piece is located, it is necessary to press it against the locating surfaces and hold it there against the forces acting upon it. The tool designer refers to this action as clamping and the mechanisms used for this action are known as clamp. 7) What is the common method of locating from circular surfaces? One of the common method of locating from a circular surface is by using cones, a method commonly referred to as conical location and usually employed when locating is done from a hole.

Closely related to conical location is V method used primarily to locate round work piece or work pieces with convex circular surface. It has been found that the best general V angle is 90o. A method of locating from a circular surface so common that it is often overlooked is the use of standard chucks. The method incorporates both locating and clamping and is often refers to as concentric location because the work is usually positioned to a common center. Chucks and work pieces revolve, however they may be quite useful for locating of a round work piece is not affected by variations in diameter and location and clamping can be accomplished quickly and readily. 8) What is meant by concentric location? Give an example. Concentric location method incorporates both locating and clamping. In this method the work is usually positioned to a common center, chucks and work pieces revolve. They may be quite useful for locating of a round work piece, because work piece is not affected by variations in diameter and location and clamping can be accomplished quickly and readily. 9) What is the difference between rest pads and rest plates? How are they used? Rest pads and plates are used to support and locate work piece vertically in a manner similar to rest buttons, but they are used with large and heavier work piece. Rest pads are similar to rest buttons but do not have a shank. They are held to the jig or fixture base plate by using socket head cup screw. They are used to support larger parts on previously machines surface. Rest pads essentially rest pads with larger bearing surface. They are used to support larger parts on previously machined surfaces, because of larger bearing surface. 10) Why are the bearing surfaces of the rest plates some times grooved? Rest plates are sometimes grooved to reduce bearing area and still provide support rigidity. This provides a space for small chips that would affect the accuracy of locating the work piece. The edge of the groove act as a chip cleaner to scrape the chips from locating surface when the work piece is slip over them.