and inking compasses tend to scratch and draw lines of irregular thickness.
This trouble calls for resharpening of the nibs, which, although not a difficult operation, requires care if satisfactory results are to be obtained.
As the nibs of both the drawing pen and the compass are of similar construction, it will suffice to consider the former only.
Fig. 102 shows a greatly enlarged and diagrammatic view of the ordinary drawing-pen nib, which has lost its original form as a result of wear ; the broken lines represent the shape of the nibs in their unworn condition.
If the tips are examined from the side with a magnifying slass, it may be found that a marked flat lias been worn as o ' '
shown in Fig. 103, where also the thickening of the point due to wear is illustrated.
The correct shape of the nibs is represented in Fig. 104, and it will be seen that the tip should be rounded when viewed from the side, and reduced to a thin edge on its other aspect.
When resharpening the blades is undertaken, the nibs are closed by means of their adjusting screw and the pen, while held in the vertical position, is worked on an Arkansas stone in the manner indicated in Fig. 105 ; the rocking motion imparted to the handle will then produce the curvature at the pen's tip.
The next step is to thin the tips of the blades on their outer surfaces only, by means of an oilstone slip ; mean-whHe. the actual edge is kept under observation with the magnifying glass to ensure that the work is carried out evenly.
When the tips of the nibs have thus been sufficiently reduced in thickness, they are separated and their contact surfaces are lightly rubbed with a slip, as shown in Fig. 106, to remove any burrs that may have been formed.
Finally, the nibs are again closed and their points are carefully rubbed with a piece of polished hard steel to give them a burnished finish. It should be borne in mind that, whilst the nibs should be sharp, they should not be so keen as to cut into the surface of the drawing paper ; the final burnishing operation, however, should prevent this.
When the pen has been cleaned with lighter fluid to remove any oil present, it should be tried under working conditions, and if the sharpening has been carefully carried out its performance should be in every way satisfactory.
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