Technical Information Fluteless Taps
Fluteless taps do not cut threads in the same manner
as conventional taps – but actually FORM and FLOW
the threads with an absence of chips. Used under
suitable conditions, these taps produce threads with
a high degree of finish not possible with ordinary
taps. Ductile materials are most appropriate for
forming of threads and must have a minimum
10% elongation.
Suitable for wide range materials
• Low carbon steels
• Leaded steels
• Austenitic stainless steels
• Alloy steels; typically up to 1200 N/mm 2 ,
(36 Rc) with a minimum 10% elongation
• Aluminium die castings alloys (low silicon, 10% max;)
• Wrought aluminium alloys (Ductile)
• Zinc die casting alloys
• Copper and copper alloys
Benefits of thread forming Whats New?
Figure 1. No chips produced
Figure 2. Higher tensile strength threads produced due to grain
structure following the thread form
Figure 3. For use in through and blind holes applications
Higher speeds and tool life
Reduced possibility of breakage due to no cutting
edges and robust tool construction Figure 4. N
ew polygon profile
Figure 5. New radiused blend on
polygon profile
Figure 6. Thread profile with
radius crest
Figure 7. Polished tool surface finish
Figure 1. Figure 4.
Figure 2.
Formed
Thread
Figure 5.
Cut
Thread
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Figure 3.
Figure 6.
Percentage of thread required
Because the thread produced by a fluteless tap is substantially stronger than a
conventional thread, greater tool life and efficiency may be obtained when forming
up to 65% thread.
Threads may be formed up to 80% of depth, but tool life will be reduced and work
clamping pressure necessarily increased. Greater tapping speeds allow the metal to flow
far more readily, so 60 feet per minute minimum may be used as a guide, but this could
increase with the type of material being tapped. A depth of 65% is recommended for the
ductile materials mentioned, but this percentage will be reduced for less ductile materials
to maintain all-round efficiency.
Tapping drill formula for fluteless taps
Refer Tapping Drill Size Chart for recommended sizes (Suitable for Unified,
Whitworth and Metric sizes only). The formula to calculate the theoretical hole size
for a required percentage of thread is:
Formula
Drill size = nominal thread dia.
(in mm)
– (0,007 x % of thread x pitch)
Example
Drill size for 65% of thread in a
M6 x 1,0 threaded hole would be:
Drill size = 6 – (0,007 x 65 x 1,0 (pitch)) = 5.54mm
(Use 5,50mm drill (Stockable drill) = 71%)
It is to be noted that the drill size for fluteless tapping is always larger than the P.D.
of the thread. A drill size equal to the P.D. of the thread would produce 100%
of thread, but this is NOT recommended.
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As the additional driving torque is only up
to 50% increase, any conventional driving
equipment using the square as a drive is
suitable for fluteless tapping.
Lubrication
In general it is best to use a good cutting oil
or lubricant rather than a coolant for fluteless
tapping. Sulphur base and mineral oils,
along with most friction reducing lubricants
recommended for use in cold extrusion or metal
drawing, have proven best for this work. Make
sure lubricant is clean, free from chips swarf
and filings in suspension, which produce a poor
finish and jamming, sometimes breakage –
extra filtration may be required.
Countersinking
Because the fluteless tap displaces metal, some
metal will be displaced above the mouth of the
hole during tapping, countersink or chamfer the
hole prior to tapping will reduce the extrusion
within the countersink and not interfere with
the mating part.
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Figure 7.