USE/CARE OF HANDTOOLS & MEASURING TOOLS - OD1621 - LESSON 2/TASK 2
FIGURE 142.
CHECKING TAP FOR STRAIGHTNESS.
(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.
(f) If the hole to be tapped is a blind hole, use a plug tap and
finally a bottoming tap to complete the tapping operation. A bottoming hole
is one in which the thread has been tapped as far as the bottom.
Use
extreme caution to keep the taps from being forced against the bottom of the
hole. Check cut threads with the proper screw pitch gage.
g. Use of Dies.
(1) General. The general procedure for cutting threads by hand is as
described in (a) through (g) below.
(a) Make certain the work to be threaded is clean and free from
burrs.
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