9 Best Bits For Drilling Hardened Steel in 2026

An 8% cobalt M42 alloy gives these bits high heat resistance and a claimed 10x life versus standard bits, so they can handle extended drilling in tough materials like stainless steel and cast iron. The surface-hardened tip is designed to penetrate hardened steel instead of skating off. Bosch’s thick web-helix design adds stability, which helps maintain control in demanding applications.

You are trading some versatility for that focused performance. The 14-piece assortment covers the most common sizes, but if you regularly need every 64th-inch increment, you’ll find the selection in the 29-piece Milwaukee set more complete. The Bosch CO14B’s compact case is great for a packed toolbox, though the smaller footprint means the bits are nestled tightly. Compared to Bosch’s own CO21 set with a three-flat shank, this model prioritizes the core cutting performance over that extra anti-spin feature.

The TiAlN coating, which withstands over 1,472°F, is the key to this set’s longevity when drilling materials like stainless steel. That heat resistance, paired with a self-centering Pilot Point tip, makes it a specialist for thin sheet metal. The geometry is engineered to cut with less downforce, which prevents the work-hardening and distortion that plague thin stock. You get cleaner holes with minimal burrs and a set that stays sharp for the long haul, backed by a 90-day satisfaction guarantee.

Engineered specifically for thin, hard, and gummy metals like stainless steel, the Crosstar M35 set tackles the common problems of bit skating and work-hardening. Its core is M35 cobalt steel, which maintains its hardness under intense local heat, and the bits feature a self-centering Pilot Point tip combined with a 135° split point. This geometry starts holes accurately on curved surfaces and requires less downforce, reducing exit burrs for cleaner results in sheet metal. For a consistent tip design across all sizes in a general-purpose cobalt set, the Bosch CO21 is an alternative. The focused engineering here, however, directly addresses the primary enemies in sheet metal work: heat and skating.

For a balance of price and performance in general steel drilling, this 29-piece M35 cobalt set is an attractive option. Expert round-ups note excellent success with these bits as a go-to for metal drilling with a cordless drill. The Milwaukee design uses a shorter, more compact bit with extended flutes, resulting in a tool that offers similar drilling depth in a solid, controllable package for common cordless use.

The trade-off is in the bit geometry; they thin out towards the tip more than some dedicated machinist bits. For the vast majority of fabrication and repair work, this isn’t an issue, but it’s something to be mindful of under extreme lateral pressure. If your work demands the absolute maximum rigidity and you’re willing to pay for it, you’d look at a set like the Bosch CO21 with its three-flat shank. For a reliable, workshop-ready set that won’t quit when the metal gets hard, Milwaukee’s Red Helix design is a pragmatic and proven solution.

Drill America’s GSC bits feature a stepped point geometry that helps them start easier and drill faster in materials like acrylic, steel, and brass. This design can be a practical advantage when creating new holes or enlarging existing ones. The cobalt construction and 135-degree split point tip are intended to increase the tool’s lifespan and reduce heat during use.

The set uses a three-flat shank to prevent spinning, but bits sized 11/64″ and smaller have a round shank instead. This means chuck grip may differ between the smallest sizes and the larger ones in the collection. For consistent drilling in hardened metals, the stepped point and cobalt material aim to provide a reliable starting point.

The 5% cobalt alloy is the key here, giving these bits the extra heat resistance needed to push through hardened steel without immediately losing their edge. This set from Irwin is for the workshop user who values a trusted name and wants a complete kit that covers nearly every common size from 1/16″ up to 1/2″ in precise 1/64″ steps. The 135-degree split point starts the hole exactly where you want it, a critical detail when working with tough materials where a wandering bit can ruin a piece.

The case measures 12.3 inches wide and 11.6 inches long, requiring more storage space than more compact sets like the Bosch CO21. This makes it better suited for a fixed workshop drawer than a portable tool bag.

A no-skate split-point tip defines this set, providing clean, precise holes and accurate starts right on your mark. That makes the Bosch CO21 a natural choice for fabrication or repair work where your first hole must be perfect, especially in slick materials like stainless steel or titanium. Cobalt construction handles the high drilling temperatures these tough materials generate, and the three-flat shank gives you a confident, slip-free grip in the chuck for bits 3/16 inch and larger.

The trade-off is in the kit’s physical footprint and scope. Its case is nine inches wide, which demands a dedicated drawer or shelf space, unlike more compact sets like the MACXCOIP. While the 21-piece range covers most common tasks from 1/16 to 1/2 inch, jobs requiring larger diameters will need a supplemental bit. For the craftsman prioritizing pinpoint accuracy over an ultra-compact kit or the largest possible bit selection, this set delivers focused reliability.

The single most decisive fact about the MACXCOIP set is its 4.1 x 3.0 inch footprint, which makes it the smallest organized kit in this guide. This is the kit you grab when your drill index is at the shop and you need a capable selection of bits for metal in your truck or home toolbox. The M35 cobalt construction and 135-degree split point are the right specs for biting into hardened steel and stainless, and the thirteen fractional sizes from 1/16″ to 1/4″ cover a solid range of common tasks. It’s a pragmatic choice for a mechanic or fabricator who needs reliable penetration in tough materials without sacrificing precious drawer space.

The trade-off for that ultra-compact design is a limited scope. You’re getting jobber-length bits, which are fine for most through-holes but won’t handle deeper drilling applications. More significantly, the top size stops at 1/4 inch, so you’ll need another set for larger holes. For a broader capability in a still-manageable package, the Bosch CO21 set extends to larger diameters. The MACXCOIP set excels as a focused, space-saving specialist, not a comprehensive workshop solution.

The triple-flute design is the standout here, delivering cleaner holes and cooler operation by ejecting chips about 40% faster than a standard bit. That means less heat soaks into your workpiece and the bit itself, which is critical when pushing through hardened steel. Combined with a TiAlN coating that shrugs off extreme temperatures, this set is built for shops that regularly tackle stainless or alloy steel. It’s for the fabricator who wants a bit that will last through the job without losing its edge and who values a precise, clean finish as much as raw drilling power.

The innovative triple-flute geometry is reserved for bits 3/32″ and larger, while the three smallest sizes use a conventional two-flute design. This makes sense for delicate work with fine bits, but it means the set’s most significant performance advantages, like improved chip ejection and superior hole finish, don’t apply across every size. For a user who needs maximum speed and finish consistency in every hole, that’s a limitation. The Crosstar set excels when you’re working within its optimized size range, offering a tangible step up in control and tool life.

The solid-bonding 1/4-inch hex shank prevents the drill bit from breaking loose from the shank base, which keeps it running straight and true in an impact driver. This design transmits torque directly and eliminates radial runout, giving you confidence when drilling into hard metals like stainless steel or cast iron. The M35 cobalt material is heat resistant and has a hardness up to 67, so it cuts faster and lasts longer than standard bits when used on hardened steel.

You trade some versatility for that rugged, driver-focused design. The size range stops at 1/4 inch, which covers a huge number of common fastener and pilot holes but leaves larger tasks for another tool. Compared to a comprehensive shop set like the 29-piece Milwaukee Red Helix, the Sinyeenglon is a specialized, portable solution. Its compact, low-profile case fits in a tool belt pouch, but the bit selection is inherently more limited. It excels at its specific mission: delivering durable, precise holes in hard metal directly from the impact driver you’re already using.