. A textbook on mechanical and electrical engineering . l point may be moved out or in to any desired radius,as indicated in Fig. 10. When the lengthening bar is used,both hands must be employed. 9. The compasses must be handled in such a manner thatthe needle point will not dig large holes in the paper. Keep § 13 GEOMETRICAL DRAWING 9 the needle point adjusted so that it will he perpendicular tothe paper, when drawing circles, and do not hear upon slight pressure will be necessary on the pen or pencilpoint, but not on the needle point. 10. The dividers, shown in Figs. 9 and 12, are usedf
. A textbook on mechanical and electrical engineering . l point may be moved out or in to any desired radius,as indicated in Fig. 10. When the lengthening bar is used,both hands must be employed. 9. The compasses must be handled in such a manner thatthe needle point will not dig large holes in the paper. Keep § 13 GEOMETRICAL DRAWING 9 the needle point adjusted so that it will he perpendicular tothe paper, when drawing circles, and do not hear upon slight pressure will be necessary on the pen or pencilpoint, but not on the needle point. 10. The dividers, shown in Figs. 9 and 12, are usedfor laying off distances upon a drawing, or for dividingstraight lines or circles into parts. The points of thedividers should be very sharp, so that they will not punchholes in the paper larger than is absolutely necessary to beseen. Compasses are sometimes furnished with two steeldivider points, besides the pen and pencil points, so that theinstrument may be used either as compasses or is the kind illustrated in Fig. 12. When using the. Fig. 12 dividers to space a line or circle into a number of equal parts,hold them at the top between the thumb and forefinger, aswhen using the compasses, and step oflf the spaces, turningthe instrument alternately to the right and left. If the lineor circle does not space exactly, vary the distance betweenthe divider points and try again; so continue until it isspaced equally. When spacing in this manner, great caremust be exercised not to press the divider points into thepaper; for, if the points enter the paper, the spacing cannever be accurately done. The student should satisfy him-self of the truth of this statement by actual trial. 11. The bow-pencil and bow-i)en, shown in Fig. 13,are convenient for describing small circles. The two pointsof the instruments must be adjusted to the same length;otherwise, very small circles cannot be drawn. To open orclose either of these instruments, support it in a vertical 10 GEOMETRICAL D
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmechani, bookyear1902
