Milling

After the thickness tolerance has been addressed, and using that datum as a base to work from, width and length tolerances can be addressed. The resulting piece will have six flat, square and parallel sides. Twin mills are ideal for this step because their opposing shell-mills address two parallel sides of the material simultaneously on each plane, guaranteeing results according to specification within .001.

This is most often the final step in addressing a surface. If customers require a special final finish, this is usually done here. If there is no further surface improvement required, the job is sent on to Quality Assurance.