Helicoil inserts are screw thread bushings coiled from wire of diamond shape cross-section. They are fit into thread tapped holes to form internal threads
with nominal size. Helicoil inserts are diametrically larger than the tapped hole. During the assembly operation, the diameter of the leading coil is reduced due to applied torque and this permits it to enter the tapped thread.
Helicoil Tap Size Chart and Calculator:
Note : * Class 2B tapped holes provide maximum production tolerances, but result
in lower locking torques when screw locking inserts are used. The higher and
more consistent torques are met by the screw locking inserts when assembled and
tested in Class 3B tapped holes.
RESULTS |
Parameter |
Value |
Nominal Size |
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Threads per inch |
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Tap Style |
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Class of Fit |
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Insert Length |
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Minimum Drilling Depth [G] |
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inch |
Minimum Countersink Diameter [Mmin]* |
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Maximum Countersink Diameter [Mmax]* |
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Minimum Tapping Depth [Tmin] |
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Minimum Major Diameter [Dmin] |
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Maximum Pitch Diameter [D2max] |
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Minimum Pitch Diameter [D2min] |
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Maximum Minor Diameter [D1max] |
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Minimum Minor Diameter [D1min] |
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Note *: Countersink angle 120° +/- 5° .
Note: The minimum drilling depths allow for countersinking the drilled hole to have a good starting thread. The drilling depths also allow 3/4 to 1 1/2 pitches insert set-down with countersink below the top surface of the tapped hole.