USE/CARE OF HANDTOOLS & MEASURING TOOLS - OD1621 - LESSON 2/TASK 2
(4) Pipe Taps.
A taper pipe tap is used for pipe fittings and on
other places where extremely tight fits are necessary.
The tap diameter,
from end-to-end of the threaded portion, increases at the rate of 3/4 inch
All threads on this tap cut, as compared to the straight taps
where only the non-chamfered portion does the cutting.
(5) Boiler Taps. Straight boiler taps range in diameter from 1/2 to
1 1/2 inches.
The chamfered portion of the thread simplifies starting.
Taper boiler taps have no chamfered portion and the threaded portion is
tapered 3/4 inch per foot. The overall and shank diameters are similar to
those of straight boiler taps.
(6) Staybolt Taps.
Staybolt taps are used principally in boiler,
locomotive, and railroad shops for tapping the staybolt holes in the outer
and inner plates or shells of boilers. The tap must have sufficient length
to tap both holes in one operation so the threads in both holes will be in
alignment. Staybolt spindle taps are also used for tapping staybolt holes.
They have a sliding removable internal spindle with a tapered guide to
ensure that both tapped holes are properly lined up.
The first hole is
tapped, then the spindle is removed, and a non-fluted thread section at the
back of the tap guides threading of the second hole.
(7) Mud or Washout Taps. Mud or washout taps have 6 flutes with a 1
1/4 inch taper per foot and 12 threads per inch.
They are used to cut
special American National or V-form threads when tapping mud plug drain
(8) Fusible Plug Tap. The fusible plug tap (not illustrated), issued
by the Army Ordnance Supply System, is made of carbon steel and has a 1 1/4
inch taper per foot.
It has a thread length of 4 3/8 inches, is 1 inch
square on the shank, has 4 flutes, and is 7 inches long.
(9) Pipe Tap and Drill. A pipe tap and drill (not illustrated) is a
combination twist drill and tap.
The tap portion follows the twist drill
tip. The tool does drilling and tapping in one operation. They are made of
carbon steel with a tapered square shank and are sized to drill and tap
holes 1/4 - 18, 3/8 - 18, and 1/4 - 14 inches long.