MACHINING Copyright Goodheart-Willcox Co., Inc. Chapter 26 Milling Machines 457 similar to the flanged vise but is fitted with a circu- lar base, graduated in degrees. This permits the vise to be pivoted on a horizontal plane and locked at any angle to the spindle. A toolmaker’s vise, Figure 26-34, permits compound or double angles to be machined without complex or multiple setups. 26.6.2 Vacuum-Operated Systems and Magnetic Chucks A vacuum-operated workholding system can be used to hold parts securely for all milling opera- tions, Figure 26-35. The system uses a plastic mat with an array of lip-edged “suckers” on the top side. Each sucker has a small hole through its center. Six lugs underneath the table secure the mat to the table. The vacuum is distributed through a grid to each of the small holes and to a holding lip edge around the circumference. The cutting tool can machine through the inex- pensive, disposable mat. This helps eliminate break- out, deburring, and other secondary operations. The mat is made of recyclable plastic. Magnetic chucks can also be used to hold work for many milling operations, Figure 26-36. However, this system is limited to holding work that is made of ferrous metal. Setup times are reduced with magnetic chucks because clamps and fixtures are not needed. Photo courtesy of Grizzly Industrial, Inc. www.grizzly.com Figure 26-34. A toolmaker’s universal vise can be tilted for compound angles. IBAG North America Figure 26-35. A vacuum-operated workholding system being used to hold a part on a vertical mill. O. S. Walker Co. Figure 26-36. A magnetic chuck can be used to hold a workpiece for some milling operations.