7/8" X 5/16" Pilots for Counterbore BoltsandNuts.com Size 1/2"-#21

Size 1/2"-#21

Carbide Tipped Die Drills are designed for drilling hardened steels in the range of 45-65 Rc

flattening

Limitless Leather™ for Extreme Abrasion Resistance

Cobalt drill bits are are effective in drilling tough

7/8" X 5/16" Pilots for Counterbore BoltsandNuts.com Size 1/2"-#21Product Description Counterboring is the enlargement of a portion of a hole that has previously been formed. If the counterbored portion is shallow (1 8" or less), the operations is usually known as spot facing; for example, a flat seat for a bolt head or nut. If, on the other hand, the hole is enlarged to a considerable depth, it is designated as counterboring. These counterbores are made of two piece construction, having an integral shank and