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A valuable and well-organized system for home education(homeschooling) 3 to 12 years.

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HOME HANDICRAFT                         341
the beginning of the curve X as you will see by looking at the top drawing. Before bending the field it may be well to de­termine on the size of cork and screws used in making the armature as you will want the end of the screws in the arma­ture to run as close as possible to the arc of the field, to ob­tain best results. As cork about an inch in diameter and two 1 1/4-inch r.-h. No. 8 screws screwed in from opposite sides will give a diameter of about 23/4 inches; the arc formed in bending the Venetian ir.on for the field should be slightly
Figure 41
greater than this. A hatpin makes a good shaft, which is hung
in bearings made from sheet brass or tin, bent over near the
top and drilled for shaft. The commutator is made from
about No. 26 sheet copper. Bend a small piece, around a
quarter-inch rod and cut at opposite side from where the edges
meet after bending, then you will have two curved pieces just
alike. These pieces may be better made from 1/4-inch copper
tubing. Now wind adhesive tape around your hatpin shaft
about one-half inch from one end until you have thickness a
little greater than the inside diameter of your two pieces of
copper. Fit these pieces which form the commutator on the
adhesive tape already wound on the hatpin, being careful that
the edges of copper do not touch each other, and hold in place X—23
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