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Use a spiral point tap (SPPT) for through holes, because it pushes the chips forward and out of the hole. Use a spiral flute tap for blind holes, because it carries the chips back out along the flutes. Use a hand tap set, taken in order, when you are threading by hand.
Hand tap sets
Hand taps typically come in sets of two or three that must be used in order. A three-piece set is a taper tap, an intermediate (second) tap and a finishing (bottoming) tap. The taper tap has the longest lead and starts the thread; the finishing tap has the shortest lead and cuts closest to the bottom of a blind hole. The set is the usual choice for tapping by hand.
Spiral point taps
A spiral point tap has its first few threads ground at an angle that pushes chips ahead of the tap. The flutes stay clear, so these taps suit through holes, and they are normally run in a machine. They are not the usual choice for a blind hole, where the chips have nowhere to go.
Spiral flute taps
A spiral flute tap has helical flutes like a drill and brings the chips back out of the hole. This is why it suits blind holes, and why it is recommended where the thread must run close to the bottom of the hole.
Where the chips go
Tap
Chips go
Hole
Hand tap set
Cut in stages by taps used in order
Through, or blind (the finishing tap reaches closest to the bottom)
Spiral point
Forward, ahead of the tap
Through
Spiral flute
Back out along the flutes
Blind
Machine and hand use
A machine tap cuts the thread in a single operation and needs rigid, accurate guidance, because it can break easily. Hand tap sets cut in stages so the work is shared between the taps. For machine tapping on a drilling machine, BVF lists a Reversible Tapping Attachment.
HSS, HSS-E and TiN in the name
HSS is high speed steel, the base material of most taps.
HSS-E is high speed steel with added cobalt, usually 5% or 8%. Cobalt raises hot hardness.
TiN is a titanium nitride coating, the gold-coloured coating applied to reduce wear.
Which should I buy?
BVF lists these taps, and the descriptions below are as given on each page:
