BS 4174:1972

Ferrous and non-ferrous. Gives general dimensions for countersunk, raised countersunk and pan head tapping screws with slotted or recessed heads, slotted mushroom heads, recessed flange heads and hexagon head tapping screws and round head metallic drive screws. Gauges for head flushness for corrosion head screws and for checking recess penetration of recessed head screws, together with testing requirements and a box with hole sizes also given.

This British Standard relates to ferrous and non-ferrous tapping screws and metallic drive screws.

Provisions are made for two classes of tapping screw, namely thread forming and thread cutting, each available in several types which are described and illustrated in the standard.

General dimensions are given for countersunk, raised countersunk, and pan head tapping screws with slotted or recessed heads, slotted mushroom heads, recessed flange heads and hexagon head tapping screws and round head metallic drive screws. Countersunk and raised countersunk head tapping screws in short lengths have shallower truncated heads than those in normal lengths and separate tables of dimensions are accordingly provided.

Details of a suitable head flushness gauge for countersunk head screws and a gauge for checking recess penetration on recessed head screws together with testing requirements for the inspection of tapping screws and approximate hole sizes for steel screws in various materials, are given with appendices.

NOTE 1 Round head screws other than metallic drive screws have not been included in this standard as it is considered that pan head screws provide for most of the applications in which round head screws are normally used and allow more conveniently for the application of torque.

NOTE 2 The titles of the British Standards referred to in this standard are given on page iii.