These are straight flute general purpose taps which can be used for
both machine or hand tapping. They are generally the most economical
tool for use on production runs, but are best on materials that produce
chips, or where the swarf breaks readily. Where deep holes are to be
tapped, in materials which produce stringy swarf, other types of taps
may be needed, especially for coarse threads.
Hand taps can be supplied in sets of three; bottom, second and taper
leads, or individually.
BOTTOM TAPS have a chamfer (lead) of 1–2 threads, the angle of
the lead being around 18 degrees per side. They are used to produce
threads close to the bottom of blind holes.
SECOND TAPS have a lead of 3-5 threads at 8 degrees per side.
They are the most popular and can be used for through holes, or blind
holes where the thread does not need to go right to the bottom.
TAPER TAPS have a lead of 7-10 threads at 5 degrees per side. The
taper lead distributes the cutting force over a large area, and the taper
shape helps the thread to start. They can therefore be used to start a
thread prior to use of second or bottom leads, or for through holes.