McMaster-Carr logo
    Forward
    Enter e-mail addresses in the fields below
    Message
    Cancel
    Print
    How can we improve?
    Comments
    E-mail address (if you would like a response)
    28 Products
    About Counterbores
    industrial info icon

    Create flat-bottomed holes, so your screw heads sit flush, recessed, or slightly raised.

    Built-In-Pilot Counterbore Sets

    Image of Product. Front orientation. Counterbores. Built-In-Pilot Counterbore Sets.
    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.
    High-Speed Steel—Durable and wear resistant, these counterbores make accurate cuts in most materials without chipping or cracking.
    For Screw Size
    No. of
    Pieces
    Shank
    Type
    No. of
    Flutes
    Each
    Uncoated High-Speed Steel
    No. 4, No. 5, No. 6, No. 8, No. 10, 1/4", 5/16", 3/8", 7/16", 1/2"
    		10Round400000000000000
     

    Built-In-Pilot Counterbores

    The pilot centers the counterbore and prevents wobbling for an accurate cut on the first try. With dimensions that match standard screw-head diameters and thread diameters, this is your plug-and-play option for pilot-driven counterbores.
    High-Speed Steel
    Image of Product. Front orientation. ZoomedIn view. Counterbores. Built-In-Pilot Counterbores.
    Durable and wear resistant, these counterbores make accurate cuts in most materials without chipping or cracking.
    Titanium Nitride (TiN) Coated—Withstand heat, corrosion, and abrasion for longer than uncoated counterbores, so the cutting edges stay sharper.
    Pilot
    Shank
    Uncoated
    Titanium Nitride
    (TiN) Coated
    For Screw
    Size
    Body
    Dia.
    Dia.
    Lg.
    Overall
    Lg.
    Dia.
    Type
    No. of
    Flutes
    Each
    Each
    1/4"
    		0.382"1/4"0.313"5 5/8"5/16"Round4000000000000000000000000000
     
    Carbide-Tipped Steel
    Image of Product. Front orientation. ZoomedIn view. Counterbores. Built-In-Pilot Counterbores.
    The hardest and most wear-resistant counterbores we offer. These bits stay sharper at higher temperatures and faster speeds for the best performance on hard and abrasive materials.
    C2 Carbide—Hard enough to cut cleanly through cast iron and nonferrous metals.
    C5 Carbide—Harder than C2 Carbide, these counterbores cut steel without damaging themselves or the hole.
    Pilot
    Shank
    Uncoated
    For Screw
    Size
    Body
    Dia.
    Dia.
    Lg.
    Overall
    Lg.
    Dia.
    Type
    No. of
    Flutes
    Each
    C2 Carbide
    1/4"
    		0.382"1/4"0.313"5 5/8"5/16"Round3000000000000000
     
    C5 Carbide
    1/4"
    		0.382"1/4"0.313"5 5/8"5/16"Round300000000000000
     

    Oversized Counterbores

    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.
    High-Speed Steel
    Image of Product. Front orientation. ZoomedIn view. Counterbores. Oversized Counterbores.
    Durable and wear resistant, these counterbores make accurate cuts in most materials without chipping or cracking.
    Titanium Nitride (TiN) Coated—Withstand heat, corrosion, and abrasion for longer than uncoated counterbores, so the cutting edges stay sharper.
    Pilot
    Shank
    Uncoated
    Titanium Nitride
    (TiN) Coated
    For Screw
    Size
    Body
    Dia.
    Dia.
    Lg.
    Overall
    Lg.
    Dia.
    Type
    No. of
    Flutes
    Each
    Each
     
    1/64" Oversize
    1/4"
    		0.398"0.266"0.313"5 5/8"5/16"Round4000000000000000000000000000
     
    1/32" Oversize
    1/4"
    		0.413"0.281"0.313"5 5/8"5/16"Round40000000000000000000000000
     
    Carbide-Tipped Steel
    Image of Product. Front orientation. ZoomedIn view. Counterbores. Oversized Counterbores.
    The hardest and most wear-resistant counterbores we offer. These bits stay sharper at higher temperatures and faster speeds for the best performance on hard and abrasive materials.
    C2 Carbide—Hard enough to cut cleanly through cast iron and nonferrous metals.
    C5 Carbide—Harder than C2 Carbide, these counterbores cut steel without damaging themselves or the hole.
    Pilot
    Shank
    Uncoated
    For Screw
    Size
    Body
    Dia.
    Dia.
    Lg.
    Overall
    Lg.
    Dia.
    Type
    No. of
    Flutes
    Each
    C2 Carbide
     
    1/64" Oversize
    1/4"
    		0.398"17/64"0.313"5 5/8"5/16"Round3000000000000000
     
    1/32" Oversize
    1/4"
    		0.413"9/32"0.313"5 5/8"5/16"Round300000000000000
     
    C5 Carbide
     
    1/64" Oversize
    1/4"
    		0.398"17/64"0.313"5 5/8"5/16"Round300000000000000
     
    1/32" Oversize
    1/4"
    		0.413"9/32"0.313"5 5/8"5/16"Round300000000000000
     

    Drill-Point Counterbore Sets

    Image of Product. Front orientation. Counterbores. Drill-Point Counterbore Sets.
    Skip a step when installing screws of various thread diameters in metal. With a sharp point on the tip, these counterbores drill a pilot hole topped with a flat recess for the screw head. That's faster and more accurate than switching to a counterbore in between passes with your drill bit.
    High-Speed Steel—Durable and wear resistant, these counterbores make accurate cuts in most materials without chipping or cracking.
    For Screw Size
    No. of
    Pieces
    Shank
    Type
    No. of
    Flutes
    Container
    Type
    Each
    Uncoated High-Speed Steel
    No. 5, No. 6, No. 8, No. 10, 1/4", 5/16", 3/8", 7/16", 1/2"
    		9Round2Plastic Case000000000000000
    No. 5, No. 6, No. 8, No. 10, 1/4", 5/16", 3/8", 7/16", 1/2"
    		9Round2Plastic Case00000000000000
     

    Drill-Point Counterbores

    Skip a step when installing screws in metal. With a sharp point on the tip, these counterbores drill a pilot hole topped with a flat recess for the screw head. That's faster and more accurate than switching to a counterbore in between passes with your drill bit.
    High-Speed Steel
    Image of Product. Front orientation. Counterbores. Drill-Point Counterbores.
    Durable and wear resistant, these counterbores make accurate cuts in most materials without chipping or cracking.
    Shank
    Uncoated
    For Screw
    Size
    Body
    Dia.
    Overall
    Lg.
    Dia.
    Type
    No. of
    Flutes
    Max. Hole
    Drilling Dp.
    Each
    1/4"
    		0.406"1 3/4"7/16"Round20.375"00000000000000
    1/4"
    		0.406"2 3/4"3/8"Round20.84"00000000000000
     

    Oversized Counterbore Sets

    Image of Product. Front orientation. Counterbores. Oversized Counterbore Sets.
    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.
    High-Speed Steel—Durable and wear resistant, these counterbores make accurate cuts in most materials without chipping or cracking.
    For Screw Size
    No. of
    Pieces
    Oversize
    Amount
    Shank
    Type
    No. of
    Flutes
    Each
    Uncoated High-Speed Steel
    No. 4, No. 5, No. 6, No. 8, No. 10, 1/4", 5/16", 3/8", 7/16", 1/2"
    		101/64"Round400000000000000
    No. 4, No. 5, No. 6, No. 8, No. 10, 1/4", 5/16", 3/8", 7/16", 1/2"
    		101/32"Round40000000000000
     

    Oversized Long-Life Counterbore Drill Bits

    Image of Product. Front orientation. Contains Annotated. Counterbore Drill Bits. Oversized Long-Life Counterbore Drill Bits.
    These counterbores are often used when screw holes in sheets or layers are misaligned. Also known as subland drill bits, they last longer than standard counterbore drill bits because the diameter stays the same after sharpening. They drill and counterbore at the same time. After drilling and counterboring, tap the hole and install your fastener. The diameters account for the 1/32” or 1/64” oversized diameter rating.
    Dia.
    Lg.
    For Screw
    Size
    Body
    Step
    Step
    Overall
    No. of
    Flutes
    Point
    Angle
    For Use On
    Each
    Uncoated High-Speed Steel
     
    1/64" Oversize
    1/4"
    		0.391"0.266"1/2"5 1/8"2118°Aluminum, Brass, Bronze, Iron, Plastic, Stainless Steel, Steel00000000000000
    1/4"
    		0.406"0.266"1/2"5 1/4"2118°Aluminum, Brass, Bronze, Iron, Plastic, Stainless Steel, Steel0000000000000
     
    1/32" Oversize
    1/4"
    		0.406"0.281"1/2"5 1/4"2118°Aluminum, Brass, Bronze, Iron, Plastic, Stainless Steel, Steel0000000000000
     

    Counterbore Drill Bits

    Image of Product. Front orientation. Contains Annotated. Counterbore Drill Bits. Counterbore Drill Bits.
    Often called step drill bits, these drill and counterbore holes at the same time. After drilling and counterboring, tap the hole and install your fastener. The body diameter may decrease after multiple sharpenings.
    Dia.
    Lg.
    For Screw
    Size
    Body
    Step
    Step
    Overall
    Point
    Angle
    For Use On
    Each
    Uncoated High-Speed Steel
    1/4"
    		0.406"0.281"11/16"5 1/4"118°Aluminum, Brass, Bronze, Iron, Plastic, Stainless Steel, Steel0000000000000
     

    Long-Life Counterbore Drill Bits

    Image of Product. Front orientation. Contains Annotated. Counterbore Drill Bits. Long-Life Counterbore Drill Bits.
    Also known as subland drill bits, these last longer than standard counterbore drill bits because the diameter stays the same after sharpening. They drill and counterbore at the same time. After drilling and counterboring, tap the hole and install your fastener.
    Dia.
    Lg.
    For Screw
    Size
    Body
    Step
    Step
    Overall
    No. of
    Flutes
    Point
    Angle
    For Use On
    Each
    Uncoated High-Speed Steel
    1/4"
    		0.375"0.250"1/2"5"2118°Aluminum, Brass, Bronze, Iron, Plastic, Stainless Steel, Steel00000000000000
     

    Counterbore Insert Holders

    Image of ProductInUse. Shown with Inserts (Sold Separately). Front orientation. Counterbore Insert Holders.

    Shown with Inserts (Sold

    Separately)

    Designed to reduce waste and costs during high-volume jobs, these counterbores consist of both an insert and a holder. When the cutting edges dull, you can replace the insert rather than the entire tool. The inserts are locked in place with a screw for a hold that’s strong enough to handle the high speeds of a CNC machine. These counterbores create flat-bottomed holes that allow socket head screws to sit flush with the surface of your material.
    Counterbore Insert Holders
    Replacement
    Insert Screws
    Dia.
    For Screw
    Size
    Body
    Shank
    Overall
    Lg.
    Max. Hole
    Drilling Dp.
    No. of Inserts
    Req.
    Each
    Pkg.
    Qty.
    Pkg.
    Steel
    1/4"
    		0.422"3/4"2 7/8"0.54"10000000000000001000000000000000
     
    Carbide Inserts
    Image of Product. Individual Carbide Insert Case. Front orientation. Counterbore Inserts.
    Image of Product. Front orientation. Counterbore Inserts.

    Individual Carbide

    Insert Case

    Inserts have a positive rake, which means the cutting edge is angled to reduce vibration and prevent thin workpieces from bending. For longer life, each insert has three cutting edges—when one edge dulls, rotate to the next one. They have chip breakers to stop long chips from forming, so they won’t block the flow of coolant or damage your tool. 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.
    Each
    Package
    IC
    Dia.
    Thk.
    Cutting
    Edge Lg.
    Tip
    Radius
    For Use On
    Each
    Pkg.
    Qty.
    Pkg.
    Titanium Nitride (TiN) Coated
    7/32"3/32"0.35"1/64"Aluminum, Brass, Bronze, Iron, Plastic, Stainless Steel, Steel000000000000001000000000000000
     
    back to top