Practical Mechanics for Boys | Page 3

Laying off hexagon nut 51 48. Cutting key-way 52
49. Key-seat rule 54 50. Filing metal round 54 51. Filing metal round
54 52. Making a round bearing 55 53. Making a round bearing 55 54.
Cross section of file 56 55. Files 58 56. Correct file movement 59 57.
Incorrect file movement 60 58. Belt lacing 69 59. Belt lacing 69 60.

Belt lacing 69 61. Belt lacing 69 62. Bevel gears 71 63. Miter gears 71
64. Crown wheel 71 65. Grooved friction gears 71 66. Valve 71 67.
Cone pulleys 71 68. Universal joint 71 69. Trammel 73 70. Escapement
73 71. Device for holding wheel 73 72. Rack and pinion 73 73.
Mutilated gears 73 74. Shaft coupling 73 75. Clutches 75 76. Ball and
socket joints 75 77. Fastening ball 75 78. Tripping devices 75 79.
Anchor bolt 75 80. Lazy tongs 75 81. Disc shears 75 82. Wabble saw
76 83. Continuous crank motion 76 84. Continues feed 76 85. Crank
motion 76 86. Ratchet head 76 87. Bench clamp 76 88. Helico-volute
spring 77 89. Double helico-volute 77 90. Helical spring 77 91. Single
volute-helix 77 92. Flat spiral or convolute 77 93. Eccentric rod or strap
77 94. Anti dead-centers for lathes 77 95. Plain circle 95 96. Ring 96
97. Raised surface 96 98. Sphere 96 99. Depressed surface 96 100.
Concave 97 101. Forms of cubical outlines 98 102. Forms of cubical
outlines 98 103. Forms of cubical outlines 98 104. Forms of cubical
outlines 98 105. Shading edges 99 106. Shading edges 99 107.
Illustrating heavy lines 100 108. Illustrating heavy lines 100 109. Lines
on plain surfaces 101 110. Lines on plain surfaces 101 111. Illustrating
degrees 102 112. Section lining 103 113. Drawing an ellipse 104 114.
Perspective at angles 106 115. Perspective of cube 107 116.
Perspective of cube 107 117. Perspective of cube 107 118. Protractor
108 119. Using the protractor 109 120. Section-lining metals 110 121.
Spur gears 122 122. Miter gear pitch 123 123. Bevel gears 124 124.
Laying of miter gears 125 125. Sprocket wheel 128 126. Simple lever
129 127. Lever action 130 128. The pulley 132 129. Change of
direction 133 130. Change of direction 133 131. Steam pressure 135
132. Water pressure 135 133. Prony brake 141 134. Speed indicator
142

PRACTICAL MECHANICS FOR BOYS

INTRODUCTORY
The American method of teaching the mechanical arts has some
disadvantages, as compared with the apprentice system followed in

England, and very largely on the continent.
It is too often the case that here a boy or a young man begins work in a
machine shop, not for the avowed purpose of learning the trade, but
simply as a helper, with no other object in view than to get his weekly
wages.
Abroad, the plan is one which, for various reasons, could not be
tolerated here. There he is bound for a certain term of years, and with
the prime object of teaching him to become an artisan. More often than
otherwise he pays for this privilege, and he knows it is incumbent on
him "to make good" right from the start.
He labors under the disadvantage, however, that he has a certain tenure,
and in that course he is not pushed forward from one step to the next on
account of any merit of his own. His advancement is fixed by the time
he has put in at each part of the work, and thus no note is taken of his
individuality.
Here the boy rises step after step by virtue of his own qualifications,
and we recognize that one boy has the capacity to learn faster than
another. If he can learn in one year what it requires three in another to
acquire, in order to do it as perfectly, it is an injury to the apt workman
to be held back and deterred from making his way upwardly.
It may be urged that the apprentice system instills thoroughness. This
may be true; but it also does another thing: It makes the man a mere
machine. The true workman is a thinker. He is ever on the alert to find
easier, quicker and more efficient means for doing certain work.
What is called "Efficiency" in labor methods, can never obtain in an
apprenticeship system for this reason. In a certain operation, where
twelve motions are required to do a certain thing, and a minute to
perform the twelve operations, a simplified way, necessitating only
eight motions, means a difference in saving one-third of the time. The
nineteen hundred fewer particular movements in a day's work, being a
less strain on the operator, both physically and mentally, to say nothing
whatever of the advantages which the proprietor of the shop would

gain.
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