Countersink bit

Countersink bits serve to machine hole surfaces after drilling, removing sharp burrs and creating a chamfer that matches the head of countersunk screws. This product range includes 90° countersink bits to DIN 335 C, flat countersink bits to DIN 373, and countersink bits with 1/4 inch hexagonal shank. Manufacturing materials include HSS high-speed steel, HSS-E with 5-8% Cobalt alloy, TiN or TiAlN coating to extend service life during continuous machining on structural steel, cast iron, and non-ferrous alloys.

The design with crosshole allows chips to evacuate along the shank direction, reducing clogging when machining deep holes. The 6.3mm hexagonal shank clamps firmly into hand drill chucks or screwdriver bits, enabling quick bit changes. Bohrcraft supplies individual bits and multi-size sets from M3 to 25mm, meeting needs from small repairs to batch production. Genuine imported products, warranty according to distributor policy.

Countersink bits serve to machine hole surfaces after drilling, removing sharp burrs and creating a chamfer suitable for countersunk screw heads. In mechanical machining, chamfering holes ensures screws sit flush, reduces stress concentration at hole edges, and enhances the aesthetic appearance of components. 90° countersink bits to DIN 335 C standard meet requirements for machining countersunk screw holes on structural steel, cast iron, and non-ferrous alloys.

HSS high-speed steel provides basic durability, while titanium coatings TiN or TiAlN extend service life during continuous machining. Cobalt 5-8% alloy enhances heat resistance, suitable for hard materials or high cutting speeds. Flat countersink bits to DIN 373 create a flat bottom for socket head cap screws, ensuring even bearing surface. The design with crosshole allows chips to evacuate along the shank direction, reducing clogging when machining deep holes.

The 1/4 inch hexagonal shank clamps firmly into hand drill chucks or screwdriver bits, enabling quick bit changes. This product range includes individual bits and multi-size sets, meeting needs from small repairs to batch production.

Classification by angle and standard

90° countersink bits to DIN 335 C constitute the majority of the range, suitable for standard ISO and DIN countersunk screws. The 90° angle creates a conical surface that matches precisely with screw heads, ensuring evenly distributed clamping force. The round shank enables clamping in hand drill chucks, bench drill presses, or CNC machine spindles. Long-shank versions serve deep holes or hard-to-reach positions, while DIN 335 Form D taper shank versions are used for industrial drill presses with Morse taper chucks.

Flat countersink bits to DIN 373 create a flat bottom instead of a conical surface, suitable for socket head cap screws or cylindrical head screws. The outer diameter of flat bits corresponds to thread sizes M3 to M10, enabling quick bit selection according to drawings. This design removes sharp burrs around threaded holes, reducing the risk of torn gloves or surface scratches during assembly. Codes 1706, 1707, and 1708 provide different sizes for threads from small to medium.

Materials and coatings

HSS high-speed steel provides basic hardness, suitable for low-carbon structural steel and gray cast iron. Bit 1700 is manufactured from HSS to DIN 335 C, meeting standard machining requirements with moderate cutting speeds. When higher service life is required, titanium nitride TiN coating in golden color reduces friction and increases surface hardness to 2300 HV. Bit 1701 with TiN coating extends service life by double compared to uncoated HSS when machining alloy steel.

TiAlN coating in purple-black color offers better heat resistance than TiN, maintaining hardness up to 800°C. Bit 1702 with TiAlN coating is suitable for stainless steel or high-alloy steel, where cutting heat increases rapidly. Cobalt 5% alloy in HSS-E steel enhances hot hardness, allowing cutting speeds 20% higher than standard HSS. Bit 1710 contains Cobalt 5%, serving machining of hardened steel or ductile cast iron. The Cobalt 8% version with Zirconium Nitride ZrN coating in code 1735 achieves surface hardness of 3000 HV, withstanding high wear during continuous machining.

Chip evacuation design

Countersink bits with crosshole allow chips to evacuate along the shank direction instead of accumulating in flutes. This design reduces cutting force and prevents chips from scratching the hole wall when withdrawing the bit. Bit 1720 is manufactured from HSS with crosshole, serving countersink machining on structural steel and non-ferrous metals. Metal chips evacuate quickly through the crosshole, enabling uninterrupted drilling processes.

The titanium TiN coated version with crosshole in code 1721 combines fast chip evacuation and high service life. TiN coating reduces friction between chips and crosshole walls, preventing chip adhesion when temperature rises. This design is suitable for batch production, where machine downtime for chip cleaning needs to be minimized. Bits with crosshole are commonly used on bench drill presses or CNC machines with chip extraction systems, utilizing compressed air flow to expel chips.

Hexagonal shank and compatibility

Countersink bits with 1/4 inch hexagonal shank clamp firmly into hand drill chucks, screwdriver bits, or quick-connect adapters. The hexagonal shank prevents slipping when torque increases, ensuring stable force transmission. Bit 1705 has a 6.3 mm hexagonal shank, designed as a specialized reamer for hole edge chamfering. The 1/4 inch size is compatible with most hand drill chucks and cordless screwdrivers on the market.

The hexagonal shank design enables quick bit changes without requiring chuck keys. Operators simply pull out the old bit and push in the new bit into the quick-connect adapter, saving time when switching between sizes. Hexagonal shank bits are suitable for assembly sites or field maintenance, where handheld tools dominate. However, when machining on bench drill presses or CNC machines, round shank or taper shank bits are still preferred due to higher concentricity.

Multi-size countersink bit sets

Countersink bit sets provide multiple sizes in one box, quickly meeting various machining requirements. The 6-piece set from 6.3 mm to 20.5 mm covers common screw sizes from M3 to M10. Set 17001330006 is manufactured from HSS to DIN 335 C, packed in an ABS box protecting bits from impact. Sizes 6.3 - 8.3 - 10.4 - 12.4 - 16.5 - 20.5 mm correspond to screws M3, M4, M5, M6, M8, and M10.

The TiN coated set in code 17011330006 extends service life when machining alloy steel. The TiAlN coated set code 17021330006 withstands high heat, suitable for stainless steel. The HSS-E Cobalt 5% set in code 17101330006 meets hard material machining requirements. Metal boxes replace ABS boxes in codes 17011410006, 17021410006, and 17101410006, providing better protection in industrial environments.

Flat countersink bit sets

The 6-piece flat countersink bit set from M3 to M10 serves threaded hole machining with socket head cap screws. Set 17061330006 with FINE BC design creates a smooth flat bottom surface, reducing stress concentration at the hole bottom. Set 17071330006 with MEDIUM BC design balances machining speed and surface quality. Set 17081330006 with CORE HOLE BC design creates deeper countersunk holes, suitable for cylindrical head screws with greater height.

SC UNEQUAL sets

SC UNEQUAL bit sets provide unequal sizes, focusing on the most commonly used diameters. The 3-piece set 17151330003 includes small, medium, and large sizes, suitable for repair shops or small assembly operations. The 5-piece sets 17151330005 and 17151332005 expand the size range, additionally covering M12 and M16 screws. The 6-piece set 17151330006 provides full coverage from M3 to M20.

The blue+ versions in codes 17191330003, 17191330005, 17191330006, and 17191332005 apply special surface treatment, increasing durability and reducing friction. The blue+ coating extends service life when machining alloy steel or ductile cast iron, reducing the frequency of resharpening or bit replacement.

Applications by industry

In steel structure fabrication, 90° countersink bits chamfer hole edges before welding or screw installation. Sharp burrs around holes cause stress concentration, prone to cracking under dynamic loads. Chamfering removes these burrs, distributing stress more evenly. Standard HSS bits meet low-carbon steel requirements, while TiAlN coated bits serve high-alloy steel or stainless steel. The 6-piece bit set enables fabrication shops to quickly meet screw sizes from M3 to M10 without purchasing individual bits.

In electronics and precision mechanical production, flat countersink bits create flat bottoms for socket head cap screws on machine housings or mounting frames. The flat bottom ensures screws sit flush, without tilting when tightened. The 1/4 inch hexagonal shank bits clamp into cordless screwdrivers, convenient for assembly line installation. The FINE BC design creates a smooth surface, reducing the risk of cracking on brittle materials such as cast aluminum or engineering plastics.

In maintenance and repair, countersink bits with crosshole help clean old holes that are rusted or deformed. Rust chips evacuate quickly through the crosshole, not accumulating in flutes. TiN coated bits withstand wear when machining hard metals or surfaces with thick oxide layers. SC UNEQUAL bit sets provide flexible sizes, suitable for mobile repair vehicles or field maintenance teams, where storage space is limited.

Usage notes

Cutting speed must match the workpiece material and bit type. Low-carbon steel accepts speeds of 20-30 m/min with HSS bits, while alloy steel requires reduction to 10-15 m/min. TiN or TiAlN coated bits allow speed increases of 20-30% compared to uncoated HSS. Excessive speed causes rapid bit heating, reducing hardness and causing premature wear. Insufficient speed increases cutting force, prone to bit breakage or hole deformation.

Feed pressure must be even and moderate, avoiding excessive pressure that breaks cutting edges. When the bit begins cutting into metal, reduce feed pressure to allow cutting edges to self-advance. Countersink bits with large diameters require less feed pressure than standard drill bits due to wider contact area. Use cutting oil when machining alloy steel or stainless steel, reducing friction and dissipating heat. Cutting oil also helps chips evacuate quickly, preventing adhesion to cutting edges.

Check cutting edge wear after each work shift. Worn cutting edges create rough surfaces, increase cutting force, and reduce accuracy. Resharpen cutting edges when wear is detected, maintaining the 90° angle and symmetry of edges. TiN or TiAlN coated bits should not be ground too deeply, avoiding damage to the coating. Store bits in sealed boxes, avoiding impact that chips cutting edges. Clean oil, grease, and metal chips after each use, preventing rust formation on steel surfaces.