What's inside
As an Amazon Associate I earn from qualifying purchases. This post may contain affiliate links at no extra cost to you.
What we cover
Cobalt Bits vs Titanium-Coated Bits for Metal Drilling
For occasional metal drilling, titanium-coated bits are usually the better value. For repeated drilling in stainless steel, hard steel, or other difficult alloys, cobalt bits are the more dependable choice.
The important difference is not simply the color. Most “titanium” bits are high-speed steel (HSS) bits with a thin titanium nitride (TiN) coating. Cobalt bits are HSS alloyed with cobalt throughout the cutting material. A coating can improve surface hardness and reduce friction, but it eventually wears through. Cobalt remains part of the cutting edge after sharpening and wear.
As an Amazon Associate we earn from qualifying purchases at no extra cost to you.
Quick comparison
| Feature | Cobalt bits | Titanium-coated bits |
|---|---|---|
| Best use | Stainless steel, hard steel, repeated drilling | Mild steel, aluminum, sheet metal, general repairs |
| Heat resistance | Very good when used at controlled speed | Good initially; coating performance declines after wear |
| Sharpening | Can be sharpened several times | Can be sharpened, but the exposed edge no longer has its original coating |
| Shock resistance | More brittle than ordinary HSS | Generally less brittle and more forgiving |
| Typical cost | Higher | Lower to moderate |
When titanium-coated bits make sense
Titanium-coated bits are a sensible choice for mild steel brackets, hinges, conduit, electrical boxes, aluminum parts, and occasional holes in thin metal. They cut cleanly when new and are commonly sold in useful general-purpose sets. If you are drilling five or ten holes for a home project, a decent titanium-coated HSS set is often all you need.
They also work well in a cordless drill because most thin metal does not require high torque. Use a regular drill or drill/driver rather than hammer mode. A titanium-coated drill bit set is a reasonable buy when the job is mostly wood, plastic, and occasional mild steel.
The main failure mode is overheating. Excessive speed, heavy pressure, or drilling without lubricant turns the cutting edge blue or dull gray. Once the coating is damaged at the tip, it does not restore itself. The bit may still drill soft material, but it will skate on steel and generate even more heat.
When cobalt bits are worth the extra cost
Cobalt bits are better for stainless steel, hardened or high-strength steel, cast iron, and production work where the same bit sees many holes. M35 cobalt HSS contains roughly 5 percent cobalt; M42 contains roughly 8 percent and is generally harder and more heat resistant. Packaging should identify the alloy if the manufacturer is being specific.
Cobalt is not magic. It does not make a dull, overheated bit effective, and it is not intended for concrete or masonry. Its advantage is that the entire HSS cutting material tolerates heat better than ordinary HSS. You can sharpen a cobalt bit and retain the underlying alloy, although incorrect sharpening can ruin the point geometry.
Choose a cobalt drill bit set if you regularly work on stainless appliances, automotive parts, machinery, or thick steel. For one small repair in mild steel, the added cost and brittleness usually are not justified.
Speed and technique matter more than the label
Metal drilling is controlled cutting, not a race. For a 1/4-inch hole in mild steel, roughly 600 to 1,000 revolutions per minute is a practical starting range. In stainless steel, start closer to 150 to 300 rpm. Larger diameters should run slower; a 1/2-inch bit may need only about 250 to 500 rpm in mild steel and approximately 75 to 150 rpm in stainless.
These are starting points, not rigid rules. Check the bit maker’s chart when available. With a cordless drill, select low gear, use the clutch only if it does not interrupt cutting force, and keep the bit straight. Apply firm, steady pressure. A proper chip should form. If the bit only rubs and produces dust-like fragments, reduce speed and increase pressure slightly.
Use cutting oil on steel and stainless steel. A few drops on the workpiece and occasional reapplication reduce friction and carry heat away. Aluminum usually cuts well with a light lubricant, though some lubricants can make chips cling to the bit. Do not use lubricant when it creates a safety problem around spinning machinery or electrical equipment.
Pilot holes and large diameters
For holes larger than about 3/8 inch, drilling a pilot hole can reduce the force required, especially with a cordless drill. Start with a bit around 1/8 inch to 3/16 inch, then step up. Do not make the pilot hole almost as large as the finish size; that leaves the larger bit with little cutting edge engagement and can cause grabbing.
For many thin-sheet-metal holes, a step bit is faster and cleaner than a standard twist bit. A metal step drill bit set is useful for electrical panels, junction boxes, and automotive sheet metal. Step bits are not the best choice for thick plate or deep holes, where a cobalt twist bit is more appropriate.
Can you use them in an impact driver?
Standard round-shank cobalt and titanium bits should not be used in an impact driver. The repeated torsional impacts can chip the cutting edges or snap the bit, particularly with brittle cobalt steel. Use a drill/driver for normal metal drilling.
If an impact driver is your only tool, use impact-rated hex-shank drill bits, keep the holes small, and expect shorter bit life. Impact-rated bits are a compromise, not a replacement for a rigid drill. A drill press gives better alignment and control for thick stock, but a cordless drill works well when the work is clamped securely.
Avoiding common failures
Clamp the metal whenever possible and remove burrs after drilling. Wear eye protection; metal chips are sharp and can eject when the bit breaks through. Stop before breakthrough if the bit starts grabbing, then reduce pressure and finish carefully. A sacrificial board behind sheet metal helps prevent a ragged exit hole.
Do not keep forcing a bit that has turned blue, squeals continuously, or produces no chips. Let it cool, inspect the cutting edges, and switch to a slower speed. For a budget-conscious tool kit, buy titanium-coated bits for routine work and keep a smaller cobalt set for stainless and hard steel. That combination covers most household and repair jobs without paying cobalt prices for holes that do not need it.