Set of 7, four 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.

Four flute counter bores offer a finer finishing cut than three flute versions. The chip removal is less aggressive. If you desire better chip removal for heavier cuts like roughing operations, consider our three flute counterbores, part #5193 indicated in the related products.

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