Set of 7, three flute cap screw counterbores with built-in pilots. These high speed steel counterbores utilize a solid pilot to keep the counterbore centered in the hole to ensure a level seat. Beginning with an initial hole, the piloted counterbore will enlarge that hole to create a flat bottom. The pilot keeps the cutter centered during this operation.

If the counterboring portion of the cut is shallow (1/8" or less) this operation is typically known as spot-facing and is used to create a flat seat for a bolt head or nut.

If the hole is enlarged to deeper depths, it is designated as counterboring and a typical application is for cap screws or bolts.

Three flute counter bores offer better chip removal for heavier cuts like roughing operations. For a finer cut, consider four flute counterbores such as our part #6680 indicated in the related products.

The counterbores in this set include sizes #6, #8, #10, 1/4", 5/16", 3/8", and 1/2".