Normal Scale
Modify > Normal Scalel
 

Description:

      The Normal Scale
(Modify > Normal Scale) tool will scale each group of selected faces in the plane perpendicular to their respective normal vectors.  Once you initialize the tool, drag to adjust the amount of the scale operation.  You can click and drag additional times to further adjust the scale amount.  Right-click or press Enter to exit the tool.


Notes:

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At first glance, the Inset Scale tool might appear to be the same as the Normal Scale tool.  Too see the difference between the two, try creating a sphere, selecting several adjacent faces, performing an extrusion (with the faces set to stay together), and then testing both inset scale and normal scale on the extruded faces.