Gear Blank

Gear blank is the work piece used for the manufacture of a gear, prior to machining the gear teeth.

Preparing Gear Blank
The blank needs to be gashed all around to produce the required teeth of the gears. The gashes or the slitting saw allow the hobbing cutter to bite and pull the blank around and the cuts act as an index for the correct number of teeth.

The midline of the gear blank needs to be held at the lathe center height and the whole blank needs to be stiff enough to resist flexure during the cutting process. Gear teeth end up exactly concentric with the bore and to this end the blank needs to turn concentric and parallel to the lathe spindle axis.

Specifications of Gear Blank

• There are seven basic specifications for gear blank dimensions and angles:
• The tolerance of the blank outside diameter and the crown to back surface distance.
• The tolerance of the outer cone angle of the gear blank.
• The tolerance of the cone surface runout of the gear blank.
• The tolerance of the side surface runout of the gear blank.
• The feeler gauge size to check the flatness of blank back surface.
• The tolerance of the shaft runout of the gear blank.
• The tolerance of the shaft bore dimension deviation of the gear blank.