Milwaukee 48-89-2318 21/64" Cobalt Drill Bit, Red Helix Design
The Milwaukee 48-89-2318 21/64" Cobalt Red Helix drill bit is a professional-grade metal drilling accessory engineered for durability and precise, repeatable performance on the jobsite. Sized at 21/64" for accurate hole diameters, this bit features cobalt construction that stands up to the heat generated when drilling through hardened metals, stainless steel, and other tough materials that quickly wear down standard high-speed steel bits. The bit's Red Helix flute geometry, a hallmark of Milwaukee's metal drilling line, is engineered to help clear chips efficiently and maintain a consistent cutting edge throughout extended use. Whether working on electrical enclosures, sheet metal panels, HVAC ductwork, or structural steel, the 48-89-2318 delivers the reliability professionals expect from Milwaukee accessories.
Key Features
- Trade Size: 21/64" diameter delivers precise, repeatable hole sizing for applications that call for an exact fit, from panel knockouts to bracket mounting.
- Durable Construction: Cobalt material formulation increases resistance to heat buildup and wear, helping the bit hold its cutting edge when drilling through stainless steel, cast iron, and other hardened metals.
- Red Helix Flute Design: Milwaukee's engineered Red Helix geometry is designed to improve chip evacuation and reduce binding for smoother, more efficient cuts in metal.
- Professional-Grade Performance: Built for contractors, electricians, and metalworking professionals who rely on consistent bit performance across repeated daily use.
- Universal Fit: Designed to work with standard corded and cordless drill and driver chucks for flexible use across jobsite tools.
- Metal Drilling Application: Purpose-built for drilling metal, making it a practical addition to any professional's drill bit set.
Technical Specifications
- Refer to manufacturer documentation for complete technical specifications.
Typical Applications
- Drilling Holes in Electrical Enclosures and Panels: creates precise openings in metal boxes and enclosures during electrical installation work.
- Metal Fabrication and Sheet Metal Work: suited for general metalworking tasks requiring clean, accurate holes.
- HVAC and Plumbing Installations: supports drilling through metal ductwork, brackets, and mounting hardware.
- Stainless Steel and Hardened Metal Drilling: cobalt construction is designed to handle tougher metal substrates than standard bits.
- General Contractor and Maintenance Applications: a versatile addition to any professional's metal drilling toolkit.
Why Milwaukee?
Milwaukee is a trusted name in professional-grade tools and accessories built to withstand the demands of daily jobsite use. The 48-89-2318 cobalt Red Helix drill bit combines heat- and wear-resistant cobalt construction with Milwaukee's engineered flute design to deliver dependable performance when drilling through metal. For contractors and tradespeople who need accessories that hold up to repeated professional use, Milwaukee's cobalt drill bit lineup, including the Red Helix design, offers the reliability the brand is known for on job sites.
Manufacturer Resources
Product Specs
- Product Type:
- Twist Drill Bit
- Department:
- Electrical
- Product Subgroup:
- Drill & Driver Bits
- Series:
- Milwaukee® Cobalt RED HELIX™ Drill Bits
- Product Group:
- Power Tools & Accessories
Milwaukee 48-89-2302 – Frequently Asked Questions
1) What sizes does the Milwaukee Cobalt Red Helix drill bit come in?
Milwaukee's Cobalt Red Helix bits are sold as single bits in nine fractional sizes: 5/64, 11/64, 13/64, 7/32, 15/64, 9/32, 19/64, 21/64 and 13/32 inch. Each size carries its own Milwaukee part number, for example 48-89-2302 for the 5/64 inch and 48-89-2318 for the 21/64 inch, so order by the size you need rather than by a set number.
2) Will a Milwaukee cobalt bit drill stainless steel without burning up?
That is what the cobalt formulation is for. Cobalt resists the heat built up when cutting hardened metals and stainless, where a plain high-speed steel bit loses its edge quickly. Keep the speed down and use cutting fluid on stainless and the edge holds through repeated holes. It is also rated by Milwaukee for cast iron and other hardened metal.
3) Can a Milwaukee 48-89-2302 cobalt Red Helix bit drill masonry or concrete anchors?
No. The Milwaukee cobalt Red Helix bits, 48-89-2302 through 48-89-2323, are built for metal drilling - electrical enclosures, sheet metal panels, HVAC ductwork, stainless steel and other hardened metals. For concrete or block, a rotary/percussion bit is the right tool instead: the Minerallac 59736 is a Relton carbide-tipped rotary/percussion bit in 1/2 inch by 6 inch. Using a cobalt twist bit in hammer mode will destroy the cutting edge.
4) What should I use instead of a Milwaukee cobalt drill bit for cutting tile or stone?
Cobalt twist bits such as the Milwaukee 48-89-2318 in 21/64 inch are formulated for heat resistance in hardened metals, not for abrasive mineral material. For tile and stone, a diamond grit bit is the appropriate type - the Lenox 12111-10DGHS is a D/S-10Dg diamond grit drill bit at 5/8 inch. The two work by different cutting actions, so they are not interchangeable.
5) Can I use these bits in a cordless drill, or do they need a drill press?
They run in standard corded and cordless drill and driver chucks, so a cordless drill/driver on the jobsite is fine. All nine sizes top out at 13/32 inch, which stays well inside the capacity of a common 1/2 inch or 3/8 inch chuck.
6) Are these the right bits for drilling out electrical enclosures and panel boxes?
Yes, that is a primary use. Electricians use them for openings in metal boxes and enclosures, bracket mounting holes, and sheet metal panel work. For larger openings such as conduit knockouts you would step up to a hole saw or knockout punch, since the largest bit in this family is 13/32 inch.
7) I need to match a bit to a tap or a specific fastener clearance. Do these cover odd fractional sizes?
They do. Alongside the common sizes the range includes the in-between fractions that tap drill charts and tight clearance holes call for: 5/64, 11/64, 13/64, 15/64, 19/64 and 21/64 inch, plus 7/32, 9/32 and 13/32. Since each size is a separate part number you can replace just the one that wears out rather than buying a whole index.
8) Is a carbide-tipped bit like the Relton 59736 a substitute for a Milwaukee cobalt bit on stainless steel?
They are not equivalents. The Milwaukee cobalt Red Helix bits, including the 21/64 inch 48-89-2318, use a cobalt formulation that resists heat buildup when drilling stainless steel, cast iron and other hardened metals, with Red Helix flutes for chip evacuation. The Minerallac 59736 is a Relton carbide-tipped rotary/percussion bit, a geometry meant for impact drilling rather than continuous-rotation metal cutting.
9) What does the Red Helix flute design actually do for me when drilling metal?
The flute geometry is cut to pull chips up and out of the hole faster. In metal that matters because packed chips are what causes binding, grabbing and a stalled drill, and trapped swarf is what cooks the cutting edge. Less binding, cleaner holes, and the edge stays sharp longer through a run of holes in a panel.
10) I need a hole larger than 13/32 inch in metal - is there an alternative to the Milwaukee cobalt Red Helix bits?
The Milwaukee cobalt Red Helix twist bits run from 5/64 inch (48-89-2302) up through 13/32 inch (48-89-2323). For larger diameters, larger-format bits in the comparable range include the Lenox 12111-10DGHS diamond grit bit at 5/8 inch and the Minerallac 59736 Relton carbide-tipped bit at 1/2 inch by 6 inch, though both are intended for different substrates rather than as drop-in metal replacements.
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Does the Milwaukee 48-89-2302 come with a warranty?
Absolutely. The Milwaukee 48-89-2302 is backed by a manufacturer’s warranty.
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