Tap - Definitions

Naming the geometries

technical drawing of the geometries of a tap

Explanation of symbols

d1 = Thread diameter
d2 = Shank diameter
d3 = Chamfer diameter
d4 = Neck diameter
d5 = Recessed square diameter
d6 = Neck diameter
d7 = Web diameter
l1 = Total length
l2 = Thread length
l3 = Useful length
l4 = Chamfer lead length
l5 = Square length
l6 = Flute length

= square dimension
Z = Number of flutes
v = Back taper (axial relief)
xr = Chamfer angle
Nb = Width of flute
m = Width of land
ha = Chamfer relief
hf = Relief on flanks
hr = Chamfer relief
αp = Relief angle
γp = Rake angle

Centerings

Table of possible centerings of taps

Manufacturing - construction dimensions

Table on DIN standards of various taps

Tap flutes

Sketch of the side view of the tap grooves shape A, C, E

Form A, C, E

  • straight-fluted
  • for through and blind holes

The flutes can hold a part of the chips. Chips get only partically removed in cutting direction. For this reason it is not recommended to use the tap for deep holes.
 

Sketch of the chip removal of the tap grooves form A, C, E
Sketch of the side view of the tap grooves shape B

Form B

  •  straight-fluted with spiral point
  • for through holes

Due to the spiral point the chips are getting removed tightly rolled in cutting direction and prevents chip-packing. Coolant-lubricant can flow freely.

Sketch of the chip removal of the tap grooves form B
Sketch of the side view of the left-twisted grooves of a tap form C, D

Form C, D

  • 8 - 15° left twisted spiral flutes
  • for through holes

Due to the left-hand spiral flutes the rake angle remains constant and ensure stable chamfer teeth to produce threads in high-strength materials. The left-hand spiral flutes forces the chips to remove ahead of the tap.

Sketch of the chip removal of the left-twisted flutes of a tap form C, D
Sketch of the side view of the right-twisted grooves of a tap form C, E

Form C, E

  • 10 - 15° right-hand spiral flutes
  • for blind holes

Especially suitable for automatic lathes and multi-spindle machines. Due to the chip removal against the cutting direction a secured tapping process is assured in hard conditions, even for threads with cross holes.

Sketch of the chip removal of the right-hand helical flutes of a tap form C, E
Sketch of the side view of the 35-50° right-twisted grooves of a tap form C, E

Form C, E

  • 35 - 50° right-hand spiral flutes
  • for blind holes

Due to the high spiral flutes, the chips can be removed securely also in long-chipping and deep blind holes.

Sketch of the chip removal of the right-hand helical flutes of a tap form C, E