Use of Jigs and Fixtures
43. Value of Jigs and Fixtures.—The use of jigs, fixtures, and other labor-saving devices is an important factor in illustrating industrial and practical applications in the school shop. It is advisable to let each group of boys work out its own jig or fixture for the particular job they have on hand.
The three most common forms of jigs are cutting jigs, boring jigs, and assembling jigs. The important reasons for the use of such devices are: (1) They illustrate the speed of output in shop work. (2) They give the student a good idea of machine operation. (3) They help in making the parts interchangeable. (4) They offer an opportunity for getting first hand information on cutting edge tools and their proper uses. (5) They show the boy the value of the use of jigs in factory work.
The toys illustrated in this book have many simple operations, such as cutting stock to length, drilling holes, surfacing, etc., that can be easily done by the use of the proper fixtures.
For that reason toys are desirable projects to be made by the productive plan. Fig. 18 shows the use of a jig and the miter box.
44. Cutting Small Wheels.—A circle of the desired size wheel may be laid out on the wood with the aid of a compass, and cut in the outline with a coping saw or band saw. Of course, it would take quite a long time by this method to make the small wheels in large quantities and besides the result would not be as good as when the wheels are made by machine.
45. Turning Wheels.—Another way to produce wheels is to turn a cylinder to the required diameter, on the turning lathe. Then cut the cylinder on the circular saw into required thicknesses of wheels desired. This method is recommended for quick work.
Fig. 18. Production of toys by use of jigs
Fig. 19. Wheel cutter in use