Общий каталог Widia 2017 - страница 1808

Tapping Speeds

Factors when trying to determine the best tapping speeds: The method of feeding the tap, and the type of equipment

• Material to be tapped for driving, also infl uences the permissible speeds. If taps are

mechanically fed at the proper rate of advance, they can be

• Length of chamfer on tap

operated at higher speeds than if they are required to feed

• Percentage of full thread to be cut themselves and pull some part of the machine along with them.
• Length of hole (depth of thread)

Speeds may be modifi ed to take into account any or all of

• Pitch of thread these factors:
• Cutting fl uids
• Speeds must be lowered as length of thread increases

because, in deep thread holes, the accumulated chips

• Machine equipment

increase friction and interfere with lubrication.

• 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 Tapping full height of thread calls for slower speed than if calculated with the same certainty, as for many other metalcutting the commercial 75% height only is required. tools. Coarse-thread taps in the larger diameters should be run With other tools, the feed per revolution can be set at any desired more slowly than fi ne-thread taps of the same diameters. point and can be varied as conditions demand. Taps, on the other The quantity and quality of cutting fl uid may affect the hand, must always be advanced at a rate equal to one pitch for permissible speeds as much as 100%. every revolution. The style of tap may vary the conditions.

• Taper threaded taps, such as pipe taps, should be

For example, with a bottoming tap, the fi rst thread on each land operated from 1/2–3/4 the speed of a straight thread tap cuts the full height of thread, while, with a taper or starting tap, a of comparable major diameter. number of threads do their share of the cutting before the full height of thread is reached. The depth of thread also varies, depending on the pitch. The coarser the thread, the greater the advance of the tap per revolution and the greater the amount of material removed.

„ RPM Formulas

SFM = Surface Feet per Minute S m/m = Surface Metres per Minute RPM = Revolutions per Minute / = 3.1416 IPM = Inches per Minute mm/min = millimetres per minute TPI = Threads per Inch P = Pitch (1/number of threads per inch)

Inch Sizes

SFM = RPM x tool diameter or 0.26 x RPM x tool diameter

3.82

RPM = 3.82 x SFM

tool diameter

IPM = RPM or *P x RPM

TPI*

Metric Sizes

S m/m = / x tool diameter x RPM 1000

RPM = mm/m x 1000

/ x tool diameter

mm/min = mm P x RPM