double helical ribbon helical screw impeller
sharp V-thread (full V-thread)
V-thread (triangular thread)
16 multislice helical CT
16-detector row helical CT
16-slice helical CT scanner
64 multi-detector helical CT
asymmetric variable pitch helical spring
axial helical structure
Backfire helical antenna
Ball helical transmission
barrel-shaped helical spring
carbide helical end mill
carbide taper shank endmill with helical teeth
complex helical drill point
Complicated helical curved surface
conic logarithmic helical line