10 Best Drill Bits For Cast Iron in 2026

Five percent cobalt alloy steel provides higher heat and abrasion resistance, making these bits suitable for tough materials without immediate dulling. The set covers sizes from 1/16 inch to 1/2 inch in 1/64 inch increments, so you have the precise diameter for most metal drilling tasks. A 135-degree split point minimizes walking on the workpiece, which helps start holes accurately on hard surfaces.

The trade-off is bulk. The case is over a foot long, which won’t fit in a compact tool bag as easily as a stubby set like the NordWolf. You’re getting a comprehensive shop set, not a portable kit.

Bosch’s CO14B bits use an M42 alloy with 8% cobalt, a material designed for high heat resistance and extended durability. According to Bosch, this composition delivers ten times the life of standard bits when drilling tough materials like stainless steel, cast iron, and titanium. The thick web-helix design provides added stability in demanding applications.

This is a focused set of 14 jobber-length bits with round shanks. Research mentions this shank type fits any standard 3/8-inch or 1/2-inch drill chuck, including those from major brands. Unlike the hex-shank Makita Impact Gold set, these Bosch bits are not designed for quick-change chucks or impact drivers.

The 1/4-inch hex shank and impact rating mean you can run these bits directly in your impact driver, turning that high-torque tool into a capable drilling machine for cast iron without changing tools. That’s a major efficiency boost for any shop where the impact driver is already in hand. The titanium nitride coating promises longer life against abrasive materials, and the 135-degree split point helps the bit bite immediately on curved surfaces. This set is built for the user who values speed and workflow integration over having every possible drill bit size.

This 14-piece titanium nitride coated set from Makita is designed for use in 1/4-inch hex impact drivers, so it fits directly into a common tool without an adapter. The TiN coating lasts 2.5 times longer than non-coated bits, which helps the set maintain its edge through more holes in materials like stainless steel and cast iron. Its 135-degree split point geometry is engineered for faster starts and reduced walking, a useful feature when working on curved or hard surfaces.

A quick-change hex shank locks these bits solidly into compatible chucks, which can help prevent slipping during use. The M35 cobalt construction and TiAlN coating provide superior resistance to abrasion and high heat, contributing to the bits’ durability. This heavy-duty design is intended for fast penetration through hard metals like stainless steel, cast iron, and titanium alloy.

The set includes two bits of the same 1/4-inch size, so it covers a single diameter rather than a range. For applications requiring multiple hole sizes, a multi-piece set like the IRWIN M35 Cobalt Drill Bit Set would be necessary. The bits are suitable for a wide range of applications, including repair, construction, or woodworking on hard materials.

Five identical 3/16 inch bits mean you can drill dozens of holes in cast iron without stopping to sharpen. This also avoids the risk of a worn bit failing mid-job. The M35 cobalt construction and pilot point tip are built for the sustained heat and hardness of cast iron, ensuring clean penetration and long tool life when you’re running a production line of parts or installing multiple fixtures.

The obvious trade-off is the lack of versatility. You get one size, so this isn’t a starter set for a general toolbox. For a broader range of sizes, you’d look at a kit like the IRWIN M35 29-piece set. But if your project calls for a specific 3/16 inch hole through cast iron, steel, or stainless, this heavy-duty five-pack delivers focused reliability and efficiency that a mixed set can’t match.

The standout feature here is the stubby length, with bits under two and a half inches long. That lets you get into cramped corners or close to a wall where a standard drill bit simply won’t fit. Combined with the quick-change hex shank, you can pop these into an impact driver for stubborn fasteners or a compact drill. The M35 cobalt composition and 135-degree split point are built for the hard, abrasive nature of cast iron, helping the bit start cleanly and resist heat. This set is for the mechanic working on an engine block or the fabricator drilling out a broken bolt in a tight frame.

The NordWolf M35 Cobalt Stubby Drill Bit Set includes just five imperial sizes, from 3/32 to 5/16 of an inch. This covers common pilot and clearance holes, but you’ll need another set for any drilling task requiring a larger diameter. Its primary advantage is its short length, which allows access to tight spaces where standard drill bits simply cannot fit.

A three-flute geometry defines the Crosstar set, providing approximately 40% improved chip ejection over conventional bits. This design promotes cooler operation by clearing debris more effectively, and the TiAlN coating withstands cutting temperatures up to 1472°F to extend tool life. For drilling hardened metals, these features combine for sustained performance with reduced heat buildup.

One limitation is that the flagship three-flute design doesn’t apply to the smallest bits in the set, which use a conventional two-flute pattern. For general-purpose drilling across a full range of sizes, a traditional jobber-length set with more pieces might be preferable. But if your primary goal is efficient, cool drilling in cast iron and other hardened metals, the Crosstar’s specialized flute design delivers a tangible performance advantage where it counts most.

The left-hand rotation is the defining feature here, turning a simple drilling operation into a potential broken fastener extraction job without swapping tools. This 13-piece cobalt set covers the essential small to mid-range sizes, and the 135-degree point tip is designed for self-centering to prevent walk-off. It’s a smart, specialized kit for anyone who regularly faces the risk of sheared screws or bolts in tough materials and wants a proactive solution built into their drill index.

This set has a focused scope. It contains strictly jobber-length bits with a standard round shank, so they won’t fit an impact driver’s quick-chuck like the NordWolf set. The maximum 1/4″ size also means you’ll need another set for larger holes. For dedicated extraction and drilling in cast iron, it’s an efficient package. For broader heavy-duty metalwork, a larger collection with more sizes might be a better long-term investment.

With 99 pieces spanning from 1/16 inch up to 3/8 inch, this set is for the shop that drills cast iron in many sizes and hates running out of bits. The cobalt M35 construction and hardened grinding are specified for hard metals like cast iron, meaning the bits should hold an edge. It’s a logical pick for a serious DIYer or a professional who needs a broad selection ready to go in one organized case. The labeled compartments make finding the right size straightforward, which saves time during a project.

Its size is the main consideration. That comprehensive assortment comes in a case nearly eight inches square, which is significantly larger than a focused set like the 14-piece BOSCH CO14B. You also must follow the instructions to the letter, as drilling cast iron requires the recommended low speed and likely some cutting fluid to keep these cobalt bits cool and lasting. It’s a set built for breadth and durability in a stationary or well-equipped shop, not for tossing in a pocket.

A 29-piece set covers sizes from 1/16″ to 1/2″, which provides a broad range for drilling holes in cast iron and other hard metals without needing another set. The bits are made from high-speed steel with a black and gold oxide coating to increase wear-resistance for tough materials. A 135° split point design helps with self-centering to prevent walk-off and allows for faster chip removal.

The set comes in a metal index case measuring 7.5 inches wide, so it occupies a standard amount of toolbox space. At 3.1 pounds, the complete kit has a substantial feel when carried. For work in extremely confined spaces, some users might prefer a more compact, stubby-style set like the NordWolf option.