Technical Information
Tapping Speeds
Factors when trying to determine the best tapping speeds:
• Material to be tapped
• Length of chamfer on tap
• Percentage of full thread to be cut
• Length of hole (depth of thread)
The method of feeding the tap, and the type of equipment
for driving, also infl uences the permissible speeds. If taps are
mechanically fed at the proper rate of advance, they can be
operated at higher speeds than if they are required to feed
themselves and pull some part of the machine along with them.
Speeds may be modifi ed to take into account any or all of
these factors:
• Speeds must be lowered as length of thread increases
because, in deep thread holes, the accumulated chips
increase friction and interfere with lubrication.
• Pitch of thread
• Cutting fl uids
• Machine equipment
• Horizontal or vertical tapping
• Bottoming taps must be run slower than plug taps.
The best and most effi cient operating speeds for taps cannot be
calculated with the same certainty, as for many other metalcutting
tools.
With other tools, the feed per revolution can be set at any desired
point and can be varied as conditions demand. Taps, on the other
hand, must always be advanced at a rate equal to one pitch for
every revolution. The style of tap may vary the conditions.
For example, with a bottoming tap, the fi rst thread on each land
cuts the full height of thread, while, with a taper or starting tap, a
number of threads do their share of the cutting before the full height
of thread is reached.
• Tapping full height of th