Page 733 - Iscar
P. 733
USER GUIDE
TAPS
Chip Explusion Results of Tap Jamming
Tap selection is also influenced by the type of hole being • torn threads
threaded. Through hole tapping usually requires a tap • short tap life
that pushes the chips out in front of the cutting edge • rejected threads
and through the other end of the hole. A bottom hole • tap breakage
tap must pull chips up and out of the hole. • scrap workpieces
Tap Mounting
The tap must be mounted on the axis of the core hole.
On non-synchronized machines (feed/speed) we
recommend the use of a tapping spindle. (ISCAR GTI,
GTIN collets, see pages 737-738)
Tapping Heads
As a rule, with non-synchronized machine spindles
(feed/ speed), the feed rate should be programmed
approximately 5-10% lower than the thread pitch.
In these cases, a tapping chuck must be used which will
compensate the difference between the feed
rate and the thread pitch.
It is important that the tension spring in the axial
compensation is set to a minimum pressure to avoid axially
loading the tap.
The compression spring should be tensioned so the tap
starts to cut by
compressing the spring up to one-half pitch.
Important
Verify that the correct speed has been selected.
Ensure that ample lubricating coolant is being used.
Machine and equipment stability are essential for
optimal performance and results.
Forming Taps
Forming taps (roll forming or cold forming) produce threads
by deforming the material near the hole walls rather than
by cutting the material. This method often works well
in ductile materials. However, in brittle materials it often
results in unsatisfactory threads.
Torque requirements for forming taps are considerably
Tap Jamming higher than for cutting taps. When forming taps are used,
Some possible causes of tap jamming are: chuck capacity must be decreased by 25%. Forming taps
• unsuitable tap do not produce chips.
• tap with incorrect cutting geometry
• unsuitable coolant for material
• insufficient coolant
• axial pressure (pull or push) on the tap
• core hole too small
• breaks in walls of core hole
• speed too high or too low
• swarf trapped in the hole
• incorrect alignment of tap and core hole
• tap eccentricity
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