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 is expressed in cubic in./min. 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 removal rate for an external grinding operation of 6" diameter shaft with a .001" depth of cut and a 12 in./min. traverse.
Removal Rate = 12 x .001 x 6 x 3.14 = .023 in3 / min.
Traverse feed depends upon the width of the wheel being used and the grinding operation being performed. For roughing, 3/4 the width of the wheel should be fed per work revolution. To find the traverse rates, the following formulas can be used.
- Traverse (ipr) = 0.75 x wheel width
Example: Find the traverse rate for a roughing operation using a 6 x 1/2 x 1/2 wheel
Traverse = 0.75 x ( 1/2 ) = .375 ipr
- Traverse (ft/min) = 0.75 x wheel width x SFM (work)
Example: Same as above with 50 SFM (work)
Traverse = .75 x 1/2 (50)
= 1.56 ft./min.
For finishing operations, a finer feed of 1/8 or less the width of the wheel per work revolution is used.
The depth cut used for roughing should be as much as the wheel can stand without breaking down. For finishing, the depth of cut is always light - .001" or less.