(b) Apply cutting oil to the tap and to the hole. Place the point of
the tap in the hole and rotate the tap (fig 37) clockwise for right-hand threads
and counterclockwise for left-hand threads.
Figure 37.
Using a tap and tap wrench.
(c) Check the tap for straightness in the hole by using a square (fig
38). Check to see that the tap is in line with the axis of the hole and at right
angles to the face of the work. Check at more than one position around the tap.
Figure 38.
Checking tap for straightness.
(d) It is not necessary to feed the tap into the hole with any pressure
as the threads will pull it in at the proper rate. Keep the tap straight.
(e) When tapping rough material, after each half turn of the tap in a
forward or cutting direction, rotate the tap a quarter turn back, then a half turn
forward, then a quarter turn back, etc, until the hole is tapped. Use pure lard
cutting oil to keep the tap well lubricated when tapping.
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