Definition - What does Helicoid mean?
A helicoid, in the context of trenchless construction, is defined as a section of auger flight. The shape of a helicoid is defined by its pitch, its inside diameter, whether it turns to the left or to the right around the drill string and the thickness of the material from which it's made.
Trenchlesspedia explains Helicoid
The helicoid is the shape of the threads of a screw. Like a screw's threads, the helicoid has a pitch that represents the angle between the threads and the screw's shaft. Inside and outside diameters are measured from the surface of the auger's string which defines the depth of the helicoid shape of the auger flight. Like any screw, the helicoid has either a left-hand twist or a right-hand twist and its length is determined by the distance required for the helicoid to make a single full turn around the auger string.