A Mid Size Vee Block
Cylindrical Post Mounted — Part Number: VB-375-CPM, For 5/16" ( 0.3125", 7.94 mm ) through 1/2" ( 0.50", 12.7 mm ) Balls
This device is designed to accept spheres from five sixteenths of an inch 5/16", 0.3125" ( 7.9 mm ), three eighths, 3/8", 0.375" of an inch ( 9.5 mm) is nominal, to one half of an inch, 1/2", 0.50" (12.7 mm) in diameter. It is our part number, VB-375-CPM.
The cylindrical mounting post is precision ground to three eighths (3/8") of an inch ( 0.375", 9.5 mm ) diameter, tolerance plus 0.0000 inches or minus 0.0005 inches (.013 mm). This post is one quarter of an inch( 1/4", 0.250", 6.35 mm ) long. The flat flange adjacent to the post is precision ground flat and square to the post. The included angle of this vee block is 90 degrees.
This device is designed for universal mounting from either the front or from behind. The major diameter of this Vee Block is three quarters (3/4") of an inch (19 mm). The flat faces of this device are precision ground with the face of the grinding wheel, not the periphery. The resulting crisscross pattern breaks up the lay of the surface texture to give this couple far superior repeatability.
There is a hole drilled through the center of the post that is tapped to accept a # 10-24 hexagon socket head cap screw, a threaded fastener. This allows the vee block to be clamped down solidly from the rear end. This same hole is counterbored from the front, which allows it to be clamped down from the front by a #6 hexagon socket head cap screw. This vee block is constructed from a very high chrome, high carbon, Martensitic stainless steel. This ultra fine-grained material is hardened to a 58 HRC minimum. These Vee Blocks are highly magnetic.
See here for Vee Block prices.