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Planing and milling
PLANING AND MILLING
A treatise on the use of planers, shapers, slotters, and various types of horizontal and vertical milling machines and their attachments.
BY FRANKLIN D. JONES
NEW YORK; THE INDUSTRIAL PRESS, 1915
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Planing and milling
PREFACE
This book deals with the practical problems connected with the adjustment and use of planers, shapers, slotters and milling machines of standard and special designs. Each subject is treated from the standpoint of the man in the shop, and a special effort has been made to present needed information pertaining to problems which the practical man often finds difficult to solve. Many operations from actual practice are illustrated and described to show the adaptability of different machines for certain classes of work, and the relation between various designs and types. Examples and operations have been selected that would not only show how a specific result is obtained, but illustrate fundamental principles and serve as a general guide. Descriptions of methods involving mathematical calculations contain the necessary rules or formulas and are accompanied by examples illustrating the problems which arise in actual practice.
While some of the material is rather elementary, many of the more advanced and difficult operations are explained, so that the book is not only a general treatise but contains much useful information of value even to experienced machinists. Detailed descriptions of different classes of planing and milling machines are given to show, in a general way, how modem machine tools are constructed and controlled, but, as far as possible, the practical application or use of the machine has been emphasized rather than its constructional details. The machines illustrated were selected as designs typical of different types, and not necessarily because they were considered superior to other machines of the same class.
Readers of mechanical literature are familiar with Machinery's 25-cent Reference Books, of which one hundred and twenty-five different titles have been published during the past six years. As many subjects cannot be covered adequately in all their phases in books of this size, and in response to a demand for more comprehensive and detailed treatments of the more important mechanical subjects, it has been deemed advisable to publish a number of larger volumes, of which this is one. This work includes Machinery's Reference Books Nos. 93, 96 and 97, together with a large amount of additional information on modem planing and milling practice. In the preparation of the subject matter, many practical methods and interesting operations were obtained from the columns of Machinery and represent approved machine-shop practice.
While some of the material is rather elementary, many of the more advanced and difficult operations are explained, so that the book is not only a general treatise but contains much useful information of value even to experienced machinists. Detailed descriptions of different classes of planing and milling machines are given to show, in a general way, how modem machine tools are constructed and controlled, but, as far as possible, the practical application or use of the machine has been emphasized rather than its constructional details. The machines illustrated were selected as designs typical of different types, and not necessarily because they were considered superior to other machines of the same class.
Readers of mechanical literature are familiar with Machinery's 25-cent Reference Books, of which one hundred and twenty-five different titles have been published during the past six years. As many subjects cannot be covered adequately in all their phases in books of this size, and in response to a demand for more comprehensive and detailed treatments of the more important mechanical subjects, it has been deemed advisable to publish a number of larger volumes, of which this is one. This work includes Machinery's Reference Books Nos. 93, 96 and 97, together with a large amount of additional information on modem planing and milling practice. In the preparation of the subject matter, many practical methods and interesting operations were obtained from the columns of Machinery and represent approved machine-shop practice.
CONTENTS
- PLANING MACHINES
- SHAPER AND SLOTTER
- PLAIN MILLING MACHINE
- UNIVERSAL MILLING MACHINE
- GEAR CUTTING IN MILLING MACHINE
- MISCELLANEOUS MILLING MACHINES
CHAPTER III - CONSTRUCTION AND USE OF PLAIN MILLING MACHINE
Milling machines are used for a great variety of operations, and many types have been designed for milling certain classes of work to the best advantage. The milling machine was originally developed in armories for manufacturing the small irregular- shaped parts used in the construction of fire-arms, and the milling process is still employed very extensively in the production of similar work, especially when intricate profiles are required and the parts must be interchangeable. Milling machines are also widely used at the present time for milling many large castings or forgings, which were formerly finished exclusively by planing; in fact, it is sometimes difficult to determine whether certain parts should be planed or milled in order to secure the best results.
Surfaces are milled by one or more circular cutters having a number of teeth or cutting edges which successively mill away the metal as the cutter rotates. These cutting edges may be straight and parallel to the axis of the cutter for milling flat surfaces, or they may be inclined to it for forming an angular-shaped groove or surface, or they may have an irregular outline corresponding to the shape or profile of the parts which are to be milled by them. An end view of a cylindrical or "plain" cutter is shown in Fig. i, which illustrates, diagrammatically, one method of producing a flat surface by milling. The cutter C rotates as shown by the arrow, but remains in one position, while the work W, which is held on the table of the milling machine and is adjusted vertically to give the required depth of cut, slowly feeds to the left in a horizontal direction. Each tooth on the periphery of the cutter removes a chip every revolution, and, as the work moves along, a flat surface is formed.
The function of the milling machine is to rotate the cutter and, at the same time, automatically feed the work in the required direction. As it is necessary to vary the feeding movement and the speed of the cutter, in accordance with the material being milled and the depth of the cut, the milling machine must be equipped with feed- and speed-changing mechanisms and other features to facilitate its operation. As the variety of work that is done by milling is almost endless, milling machines differ widely as to their form, size and general arrangement. Some are designed for doing a great variety of work, whereas others are intended for performing, as efficiently as possible, a comparatively small number of operations. Some machines are arranged for rotating the cutter horizontally, whereas with other types, the cutter rotates about a vertical axis. In this treatise, no attempt will be made to describe all the different types of milling machines, but rather to refer briefly to the more common designs, and then to illustrate their application and the principles of milling by showing typical examples of common milling operations.
Plain Milling Machine. - A type of milling machine that is widely used, especially for milling large numbers of duplicate parts, is shown in Fig. 2. This is known as a plain, horizontal milling machine of the column-and-knee type. The principal parts are the column C and knee K^ the work-table T, the main spindle S which drives the cutter, and the speed- and feed-changing mechanisms encased at A and B, respectively. The spindle receives its motion from belt-pulley P at the rear. This pulley is connected to the driving shaft by a friction dutch operated by lever M which is used for starting and stopping the machine. When the friction clutch is engaged, power is transmitted to the main spindle S through gearing, and, by varying the combination of this gearing, the required speed changes are obtained. Knee K is free to slide vertically on the front face of the column, and it carries saddle Z and the table T. The saddle has an in-and-out or cross movement on the knee, and the table can be traversed at right-angles to the axis of the spindle. Either of these three movements, that is, the longitudinal, cross, and vertical movements can be effected by hand or power. The hand movements are used principally for adjusting the table and work to the required position when starting a cut, whereas the automatic power feed is employed when milling. The hand-crank D is used for raising or lowering the knee with its attached parts, handwheel E is for the cross-feed of the saddle and table, and handle F is for the longitudinal adjustment of the table. The table can also be traversed rapidly by the large handwheel N at the front of the machine.
The work to be milled is held either in a vise V, or it is attached to the table by other means. When duplicate parts are to be milled in quantity, they are usually held in a special fixture bolted to the table in place of the vise.
The Speed-changing Mechanism. - The speed of the spindle is varied by changing the positions of the levers L, Li, and the handwheel W, Each lever has two positions, making four in all, which are marked with the letters A, B, C and D, and the positions for the handwheel are numbered i, 2, 3 and 4. An index-plate or table attached to the casing shows just what the speed will be for any position of the levers.
The Feed-changing Mechanism. - The power-feed mechanism at B transmits its movement to the front of the machine by shaft U equipped with universal joints and a telescopic connection to permit raising or lowering the knee on the column. Shaft U drives gearing in the feed-tripping and reversing box G, and from this point the power is transmitted to the knee, saddle or table, as may be required. The table feed is engaged or disengaged by lever Y and it is controlled by another lever located at Q, but not seen in the illustration. The direction in which lever Q is inclined from the vertical determines the direction of the table feed.
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Surfaces are milled by one or more circular cutters having a number of teeth or cutting edges which successively mill away the metal as the cutter rotates. These cutting edges may be straight and parallel to the axis of the cutter for milling flat surfaces, or they may be inclined to it for forming an angular-shaped groove or surface, or they may have an irregular outline corresponding to the shape or profile of the parts which are to be milled by them. An end view of a cylindrical or "plain" cutter is shown in Fig. i, which illustrates, diagrammatically, one method of producing a flat surface by milling. The cutter C rotates as shown by the arrow, but remains in one position, while the work W, which is held on the table of the milling machine and is adjusted vertically to give the required depth of cut, slowly feeds to the left in a horizontal direction. Each tooth on the periphery of the cutter removes a chip every revolution, and, as the work moves along, a flat surface is formed.
The function of the milling machine is to rotate the cutter and, at the same time, automatically feed the work in the required direction. As it is necessary to vary the feeding movement and the speed of the cutter, in accordance with the material being milled and the depth of the cut, the milling machine must be equipped with feed- and speed-changing mechanisms and other features to facilitate its operation. As the variety of work that is done by milling is almost endless, milling machines differ widely as to their form, size and general arrangement. Some are designed for doing a great variety of work, whereas others are intended for performing, as efficiently as possible, a comparatively small number of operations. Some machines are arranged for rotating the cutter horizontally, whereas with other types, the cutter rotates about a vertical axis. In this treatise, no attempt will be made to describe all the different types of milling machines, but rather to refer briefly to the more common designs, and then to illustrate their application and the principles of milling by showing typical examples of common milling operations.
Plain Milling Machine. - A type of milling machine that is widely used, especially for milling large numbers of duplicate parts, is shown in Fig. 2. This is known as a plain, horizontal milling machine of the column-and-knee type. The principal parts are the column C and knee K^ the work-table T, the main spindle S which drives the cutter, and the speed- and feed-changing mechanisms encased at A and B, respectively. The spindle receives its motion from belt-pulley P at the rear. This pulley is connected to the driving shaft by a friction dutch operated by lever M which is used for starting and stopping the machine. When the friction clutch is engaged, power is transmitted to the main spindle S through gearing, and, by varying the combination of this gearing, the required speed changes are obtained. Knee K is free to slide vertically on the front face of the column, and it carries saddle Z and the table T. The saddle has an in-and-out or cross movement on the knee, and the table can be traversed at right-angles to the axis of the spindle. Either of these three movements, that is, the longitudinal, cross, and vertical movements can be effected by hand or power. The hand movements are used principally for adjusting the table and work to the required position when starting a cut, whereas the automatic power feed is employed when milling. The hand-crank D is used for raising or lowering the knee with its attached parts, handwheel E is for the cross-feed of the saddle and table, and handle F is for the longitudinal adjustment of the table. The table can also be traversed rapidly by the large handwheel N at the front of the machine.
The work to be milled is held either in a vise V, or it is attached to the table by other means. When duplicate parts are to be milled in quantity, they are usually held in a special fixture bolted to the table in place of the vise.
The Speed-changing Mechanism. - The speed of the spindle is varied by changing the positions of the levers L, Li, and the handwheel W, Each lever has two positions, making four in all, which are marked with the letters A, B, C and D, and the positions for the handwheel are numbered i, 2, 3 and 4. An index-plate or table attached to the casing shows just what the speed will be for any position of the levers.
The Feed-changing Mechanism. - The power-feed mechanism at B transmits its movement to the front of the machine by shaft U equipped with universal joints and a telescopic connection to permit raising or lowering the knee on the column. Shaft U drives gearing in the feed-tripping and reversing box G, and from this point the power is transmitted to the knee, saddle or table, as may be required. The table feed is engaged or disengaged by lever Y and it is controlled by another lever located at Q, but not seen in the illustration. The direction in which lever Q is inclined from the vertical determines the direction of the table feed.
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