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  • Points of screws shall be tapered and fluted or slotted as illustrated above for the respective types. The flute on Type T screws shall have an included angle of 90º to 95º and the thread cutting edge located above the axis of screw. Tapered threads shall have unfinished crests, and the flutes or slots shall extend through the first full thread beyond taper except for Type F screws on which tapered threads may be complete at manufacturer's option and flutes may be one pitch short of the first full form thread. Other details of taper and flute design shall be optional with the manufacturer, provided the screws meet the specified performance requirements.
  • Where specifying nominal size in decimals, zeros preceding decimal and in the fourth decimal place shall be omitted.
  • Screws of these nominal lengths and shorter shall have point taper lengths specified for short screws. Longer lengths shall have point taper lengths specified for long screws.
Unit of Measure

Manufacturer

Manufacturer

N/A Industrial Fasteners Institute

Specifications

Product

N/A Tapping Screws

Unit of Measure

N/A English

Nominal Size or Basic Screw Dia.

N/A 1/4 in

Nominal Size or Basic Screw Dia. (Decimal)

N/A 0.2500 in

Max. Major Dia. (D)

N/A 0.2500 in

Min. Major Dia. (D)

N/A 0.2408 in

Ref. Point Dia. (P)

N/A 0.200 in

Max. Point Taper Length For Short Screws (S)

N/A 0.175 in

Min. Point Taper Length For Short Screws (S)

N/A 0.125 in

Max. Point Taper Length For Long Screws (S)

N/A 0.225 in

Min. Point Taper Length For Long Screws (S)

N/A 0.175 in

Determinant Lengths for Point Taper 90º Heads (L)

N/A 13/32 in

Determinant Lengths for Point Taper Csk Heads (L)

N/A 17/32 in

Min. Practical Nominal Screw Lengths for 90º Heads (L)

N/A 3/8 in

Min. Practical Nominal Screw Lengths for Csk Heads (L)

N/A 1/2 in

Codes and Standards

Codes and Standards

N/A ASME B18.6.4 1998

Threads Per Inch

Threads Per Inch

N/A 20