There are many characteristic variables in the grinding process. At this point we focus on just two of the most important in practice: the specific time-machining volume and the "G" value.

Specific time-machining volume Qw‘

The specific time-machining volume, also known as Qw‘, describes the removal capacity of a grinding wheel in cubic millimeters per millimeter of grinding rim width per second. This allows a direct comparison of various grinding processes and to evaluate the actual removal capacity. Also, Qw‘ is often used to calculate the feed control.

Grinding tools

Legend: ae = feed in mm
Vt = advance speed in mm/min
Dw = workpiece diameter mm
Nw = rotary speed of workpiece in rpm
Vf = radial feeding speed (advance) in mm/min.

The G value is a ratio number. It corresponds to the ratio of material removed from the workpiece in cubic millimeters and the grinding rim volume required for this operation, also measured in cubic millimeters. Naturally, the G value makes sense only when directly comparing different grinding wheels used in identical grinding processes and with identical parameters.

The general guide values for the G value when using Diamond and CBN wheels are:

Diamond on carbide metal: 50–300
CBN on HSS: 150–800



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