Application Guide Troubleshooting - Taps
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Problem
1 Thread is oversize
2 Axial miscutting of thread
3 Thread is undersize
4 Thread has bellmouthed entry
5 Thread surface is rough and unclean
6 Low tool life
7 Partial or complete tap breakage on FORWARD or BACKWARD movement
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Possible reason Solution
Wrong tap, cutting geometry of the
tap is not suitable for this operation Use correct tap for the material group
(see Expert Tool System, at www.suttontools.com)
Tap hole diameter should be in accordance to DIN336
or respective standard. For cold forming taps, a special
hole diameter is needed.
a) check workpiece clamping
b) check machine settings
a) use mechanical feed
b) use tap holder with length compensation
a) use a new tap
b) improve and check lubrication
c) remove cold welding area from tap
d) use tap with surface treatment or coatings
a) use mechanical feed
b) use tap that has better guiding characteristics
a) improve lubrication
b) lower speed
a) use tap with different flute form
b) use coated taps
c) use tap set
Make sure that the coolant is correct and
that the supply is sufficient
Spiral fluted taps should only be lightly pushed into the
tap hole until it begins to cut. The tap holder should
immediately begin to apply tension to the tap.
Spiral pointed taps and even left hand spiral flute taps
must have a stronger pressure until they begin to cut.
The tap holder should immediately begin to apply
pressure to the tap (pushing force)
Tap hole diameter is undersize
Misalignment - tap hole position,
or angle is not correct
The axial machine spindle movement
is not free and easy
Cold welding on the thread flanks
of the tap
Poor guidance of the tap because
of little thread depth
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Speed is too high
Chip clogging
• The lubrication wrong, additives
or the coolant supply is not sufficient
Spiral fluted taps are over pressured
in the initial cutting phase
(retracting pulling force)
• Spiral pointed taps (gun taps) are not
receiving enough pressure in the initial
cutting phase
Tolerance on the tap is not identical
to the tolerance on the drawing or
on the gauge
Wrong initial cutting pressure has been
used or the machine spindle is not
moving along its axis free and easy
Tap is over loaded, either from coarse
pitch and/or tough material
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Cold welding, material build-up (pick-up)
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Hardened walls in drilled hole
Over loading of teeth in the chamfer area
Use a tap which has a correct tolerance
a) use mechanical feed
b) use tap holder with length compensation
Use set of taps
a) improve coolant supply, use taps with surface
treatments or coatings
b) check if surface treatment is correct for
this application
a) use drill best suited to material being drilled
b) use new drill or boring tool
c) resharpen drilling or boring tools
d) if possible, heat treatment and coatings should only
be m