Helical Gears or Helical Spur Gears:

In this, the teeth make an angle along the axes of the gears that is called helix angle. The two meshing gears contain same helix angle however its layout is in opposite sense as illustrate in  given Figure

   Helical Gears

The contact among two teeth takes place at a point of the leading edge. The point moves along with a diagonal line across the teeth. This results in slow transfer of load and decrease in impact load and so drop off in noise. The helical gears introduce thrust along with the axis of the shaft that is to be borne by thrust bearings.