Create flat, close-fitting recesses for a range of screw-head sizes. The pilot centers and stabilizes the counterbore for an accurate cut and even surface on the first try.

A handful of counterbores and changeable pilots give you the versatility of dozens of normal counterbores. For each hole, mix and match counterbores and pilots to correspond with your screw-head and screw-shank diameter.

Drill and counterbore holes of different depths without changing tools. These counterbores move along the drill bit (sold separately) and lock into place with set screws to match the length of the screw you're installing.

Designed to give screw heads a slightly loose fit, these counterbores are a bit wider than standard sizes. The extra clearance prevents binding and leaves room for a seal or O-ring around the screw head.

Replace dull edges instead of buying new counterbores to reduce costs during high-volume jobs. These kits come with all you need to cut precise port holes for hydraulic fittings, including a holder and two types of replaceable inserts. The pilot insert guides the counterbore as it penetrates material, and the form inserts finish the hole to the exact size you need. Secure the inserts with the included screws so they stay in place, even at the high speeds of your CNC machine. These kits meet aerospace and military specifications for leakproof port holes, so fittings stay sealed over time, even during sudden pressure and vibration. When you need to cut threads in the hole, use the included thread mill.

Replacement inserts come factory sealed from the manufacturer for maximum traceability. The replacement form insert screw for 9816N12 can also be used to secure the pilot insert.

Replacement Pilot Inserts—Each of these inserts has three cutting edges for a long life—just rotate to a new edge when one becomes dull. They have a positive rake, which means the cutting edge is angled to reduce vibration and prevent thin workpieces from bending. Built-in chip breakers prevent long chips that can block the flow of coolant or damage your counterbore.

Inserts sold individually come packed in a clear plastic case to protect cutting edges during shipment. Inserts sold in packs come factory sealed from the manufacturer for maximum traceability.

All you need to machine precise port holes for hydraulic fittings, including a drill bit, port counterbore, and thread mill. These tools meet aerospace and military specifications for leakproof port holes, so fittings stay sealed over time, even during sudden pressure and vibration. With multiple cutting edges, the drill bit roughs out a hole with the right shape for the counterbore to finish. A built-in channel delivers coolant to the cutting surface to reduce heat and flush out chips more efficiently than a standard drill bit can. The counterbore has a pilot that guides the tool as it finishes the hole to the exact size you need for your fitting. Use the thread mill to cut internal threads. The mill leaves enough space in the hole for chips—or even a broken mill—to fall without damaging the workpiece.

All tools are coated with aluminum titanium nitride (AlTiN) to reduce heat as you cut and extend tool life. While they’re most often used to make holes in aluminum and steel, you can also use them on hard metals like stainless steel.