The following resources require a paid premium monthly or annual membership for access. Should you find any errors omissions broken links, please let us know - Feedback Open: Jig and Fixture Design Manual The book is written as a textbook and reference source, and is meant to be used by the experienced practitioner as well as the beginner, whether he is a technician in industry or a college student. The author concentrates on three major objectives: 1 to describe the fixture components in full; 2 to present the fundamental principles for efficiently combining the components into successful fixtures; and 3 to apply basic engineering principles to the mechanical and economic analysis of the complete design. These three tasks are supported by a comprehensive description of com mercjally available fixture components, a four-point, step-by-step method and comprehensive check list for the design procedure, applicable equally to all types of fixtures, and also calculation methods for the stress and deformation analysis of the fixture body and its major components. The use of a variety of calculation methods is demonstrated by numerical examples. The author has avoided presenting a confusion of detailed drawings of complicated fixtures.
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In the text the metric data are put in parentheses following the English data; in tables the metric units are usually placed in separate columns. The accuracy with which the conversions are performed varies with the nature and purpose of the data quoted.
Several tables for the conversion of inches and millimeters, feet and meters, and pounds and newtons are presented in Appendix IV. The purpose is to present the result of the conversion in a manner representative of the equivalent level of workshop accuracy.
In other cases, Lc, when dimensions include fractions of an inch, approximations are used. There are also cases where a fairly close approximation would be meaningless, and where it is more realistic to present the result of the conversion in a round number of millimeters. When, for example, a fixture is made with an overall length of 16 inches, then this dimension is obviously chosen by the designer as a convenient round value, and not as the result of an accurate calculation.
If the same fixture had been designed in a metric country, the designer would not choose the length as 16 X Likewise, an American component manufacturer may market an eyebolt 6 inches in length, while a European manufacturer may have an equivalent eyebolt that is mm, not Where an American screw thread is converted, it is to the nearest metric screw thread.
No attempt is made to convert American standard fits and tolerances. In some cases, such as in dimensioned drawings and their accompanying calculations, no conversion is attempted.
To write two different sets of dimensions into the drawings and detailed calculations would be confusing. The purpose of such calculations is to explain the method, rather than to illustrate one particular size of an object. Also, for some of the commercial components concerning a specific American product, only English dimensions are quoted. Other equations, of an empirical nature, include numerical coefficients the values of which depend on the type of units used.
In all such cases, separate equations are given for use with English and with metric units. In most of the numerical examples, the given data as well as the calculated end results are stated in English as well as in metric units.
It should be noted that conversions have been made to units in the International System SI which is rapidly becoming the recognized standard throughout the world, Thus the reader will find that the newton N and the kilonewton kN are the metric units used for force while the gram g and the kilogram kg are used for weight mass. Preface The book is written as a textbook and reference source, and is meant to be used by the experienced practitioner as well as the beginner, whether he is a technician in industry or a college student.
The author concentrates on three major objectives: 1 to describe the fixture components in full; 2 to present the fundamental principles for efficiently combining the components into successful fixtures; and 3 to apply basic engineering principles to the mechanical and economic analysis of the complete design. These three tasks are supported by a comprehensive description of commercjally available fixture components, a four-point, step-by- step method and comprehensive check list for the design procedure, applicable equally to all types of fixtures, and also calculation methods for the stress and deformation analysis of the fixture body and its major components.
The use of a variety of calculation methods is demonstrated by numerical examples. The author has avoided presenting a confusion of detailed drawings of complicated fixtures.
Instead, there are 15 actual cases included, ranging from the simplest drill plate to some complex and quite advanced fixtures for milling and other operations. For each category of machining operations, there is a definition of its characteristic fixture requirements and one or more typical examples. In addition, the book includes the design principles for fixtures of the most important non-machining operations, such as welding and assembly.
A number of the line drawings in the book are executed in a recently introduced drawing style in which two line thicknesses are used for edges and contours. The heavier lines indicate the contours of surfaces that are surrounded by air. With the dominant position of the metric system outside of the United States and the approaching introduction of this system within this country, metric units are used together with the English units throughout the book.
Four informative appendices with illustrations should prove to be helpful to the reader, they are "Measuring Angles in Radians," "Transfer of Tolerances from the Conventional Dimensioning System to the Coordinate System," "Dimensioning of Fixtures," and lastly, "Metric Conversion Tables of Linear Measure.
As a general rule it is provided with devices for supporting and clamping the workpiece. In addition, it may also contain devices for guiding the tool prior to or during its actual operation.
Thus, a jig is a type of fixture with means for positively guiding and supporting tools for drilling, boring, and related operations.
Hence, the drill jig, which is usually fitted with hardened bushings to locate, guide, and support rotating cutting tools.
The origin of jigs and fixtures can be traced back to the Swiss watch and clock industry from which, after proving their usefulness, they spread throughout the entire metal working industry. The main purpose of a fixture is to locate the work quickly and accurately, support it properly, and hold it securely, thereby ensuring that all parts produced in the same fixture will come out alike within specified limits. In this way accuracy and interchangeability of the parts are provided.
It also reduces working time in the various phases of the operation, in the setup and clamping of the work, in the adjustment of the cutting tool to the required dimensions, and during the cutting operation itself by allowing heavier feeds due to more efficient work support. Jigs and fixtures expand the capacity of standard machine tools to perform special operations, and in many cases, they make it possible to use plain or simplified, and therefore less expensive, machinery instead of costly standard machines.
In other words, they turn plain and simple machine tools into high production equipment and convert standard machines into the equivalent of specialized equipment. By maintaining or even improving the inter-changeability of the parts, a jig or fixture contributes to a considerable reduction in the cost of assembly, maintenance, and the subsequent supply of spare parts.
In effect, jigs and fixtures reduce costs and improve the potential of standard machines and the quality of the parts produced. The skills of the experienced craftsmen, designers, and engineers are permanently built into the fixture and are thereby made continuously available to the unskilled operator.
One important goal is to design a fixture in such a way as to make it foolproof, and thereby contribute to added safety for the operator as well as for the work. Application and Classification of Jigs and Fixtures The obvious place for jigs and fixtures is in mass production, where large quantity output offers ample opportunity for recovery of the necessary investment.
However, the advantages in the use of jigs and fixtures are so great, and so varied, that these devices have also naturally found their way into the production of parts in limited quantities as well as into manufacturing processes outside of the machine shop, and even outside of the metalworking industry. The many problems of geometry and dimensions encountered within the aircraft and missile industry have greatly accelerated the expanded use of jigs and fixtures.
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