Thread Forms and Point Types: Type-A, BSB, CSB, Hi-Low, TEK#1–#5, Type 17

Six thread forms

Type-A, BSB, CSB, hi-low, machine and double. Type-A is the coarse sheet metal thread; BSB and CSB are the blunt and cone point sheet metal forms; hi-low uses two thread heights to cut torque and raise pull-out; machine thread runs into a tapped hole or nut; double thread has two starts, so the screw advances twice as far per turn.

Six point types

TEK#1 to TEK#5 and Type 17. The TEK number follows the total thickness of steel the point must drill before the thread engages — get it wrong and either the screw stalls or the two layers jack apart. Type 17 is the timber point: cut away so it clears its own chip and starts in wood without a pilot hole.

Wings and serrations

A winged point reams a clearance hole through the top layer — timber, or a top sheet — so the thread only engages the material underneath. The wings then snap off when they reach the steel. Without them the thread bites the top layer while the point is still drilling, and the joint opens up. Serrations under a flat head let it countersink itself without pre-drilling.

Standard thread pitches

10#-12, 12#-11 and 14#-10 on the coarser sizes; 6#-20, 7#-19, 8#-18 and 10#-16 in the middle; 8#-32, 10#-24, 12#-24 and 14#-20 on the finer machine-thread end.

Everything on this page describes the specification range Beyond Industry Groups Limited works to. Where a figure is a laboratory test result rather than a service life, it is described as such.