Metal Removal Rate - Tool Post Grinders
For most tool post grinding operations, the material removal rate is dependent upon three factors: work diameter, depth of cut and traverse rate. The removal rate is expressed in cubic inch per minute (in3), and can be found using the following equation:
Removal Rate = Traverse (in/min) x Depth (in) x Work Diameter (in) x 3.14
Example: Find the metal remove rate for an external grinding operation on a 6” diameter shaft, with a 0.001” depth of cut and 12 in/min traverse. Removal Rate = 12 (in/min) x 0.001 (in) x 6 (in) x 3.14 = 0.23 in3/min
Traverse feed depends upon the width of grinding wheel being used and the grinding operation being performed. For roughing, 3/4 the width of the grinding wheel should be fed per work revolution. For finishing operations, a finer feed of 1/8 or less the width of the grinding wheel per work revolution is used. To find the traverse rates, the following formulas can be used.
Traverse (ipr) = 0.75 x Grinding Wheel Width (in)
Example: Find the traverse rate for a roughing operation using a 6” diameter x 1/2” wheel thickness x 1/2” bore grinding wheel. Traverse = 0.75 x 1/2 (in) = 0.375 ipr
Traverse (ft/min) = 0.75 x Grinding Wheel Width (in) x sfm (work)
Example: Same as above with 50 sfm (work)
Traverse = 0.75 x 1/2 (in) x 50 sfm = 1.56 ft/min
Depth of Cut
The depth of cut used for roughing should be as much as the grinding wheel can stand without breaking down. For finishing, the depth of cut is always light – 0.001” or less.