Rolled vs Ground Drill Bits

Whether you are a weekend DIYer or a professional tradesperson, you’ve found two nearly identical drill bits with similar attributes and different price tags. One is labeled HSS-R (Rolled) and the other HSS-G (Ground).

While they might look similar at a glance, the way they are manufactured changes how they perform, how long they last, and—most importantly—which projects they are actually suited for.

In this Insight, we’ll break down the "Rolled vs. Ground" debate to help you decide which one belongs in your toolbox.

	ROLLED	GROUND
Manufacturing	Heated and twisted (roll-forged)	Ground from a solid hardened block
Accuracy	Lower; can have slight geometric errors	Extremely high; very precise diameters
Sharpness	Standard; edges can be slightly "softer"	Razor-sharp; stays sharp longer
Surface Finish	Rougher flutes; typically black (steam oxide)	Polished flutes; usually silver/bright finish
Durability	High; more flexible/less likely to snap	High hardness; more brittle under side-loads
Cost	Inexpensive	Moderately expensive

Rolled Drill Bits

What Is A Rolled Drill Bit (HSS-R)?

Rolled drill bits are made by heating the steel and then "roll-forging" it into a spiral shape.

Positive Points About Rolled Drill Bits

Cost-Effective: Because the process is fast and efficient, these are the most affordable bits on the market.
Toughness: The forging process maintains the grain structure of the steel, making the bit slightly more flexible. If you are using a hand drill and aren't perfectly steady, a rolled bit is less likely to snap under pressure.

Negative Points About Rolled Drill Bits

Lower Precision: The heating and rolling process can lead to slight geometric variations.
Rougher Surface: The "flutes" (the grooves that pull dust out) are rougher, which can lead to friction and heat buildup.

Ground Drill Bits

What Is A Ground Drill Bit (HSS-G)?

Ground bits are manufactured through a more intensive process. Instead of being twisted into shape, they are ground out of a solid, hardened block of high-speed steel using precision machinery.

Positive Points About Ground Drill Bits

High Precision: These bits are perfectly symmetrical and have incredibly accurate diameters.
Superior Sharpness: Because the cutting edges are ground, they are razor-sharp right out of the box and stay sharp longer.
Cooler Drilling: The polished flutes allow metal shavings (chips) to slide out effortlessly, reducing heat and extending the life of the bit.

Negative Points About Ground Drill Bits

Higher Price: Precision comes at a cost; you can expect to pay significantly more for a set of HSS-G bits.
Brittle: While they are harder, they are also less flexible. If you tilt your drill mid-hole, a ground bit is more likely to snap than bend.

Rolled vs Ground: Other Factors To Consider

Grain Structure

Rolled (HSS-R): Think of this like kneading dough. The rolling process "pushes" the steel fibers into the spiral shape. This preserves the grain flow of the metal.
- The Benefit: This makes the bit more "ductile" (flexible). If the bit binds in a hole, it will often twist or bend slightly before it snaps.
Ground (HSS-G): This is a subtractive process. The machine cuts right through the grain of the hardened steel to create the flutes.
- The Benefit: This leaves the steel in its most rigid state. It won't flex, which ensures the hole stays perfectly straight, but if it binds, it will shatter like glass rather than bend.

Flute Surface and "Chip Evacuation"

The manufacturing process changes the inside of the "valves" (flutes) where the waste material travels.

Rolled bits have a slightly pebbled or rougher texture inside the flute. This creates more friction, which is why they get hot faster.
Ground bits have "polished" flutes. You can actually see your reflection in a high-quality ground flute. This allows the hot metal chips to "flow" out of the hole like water, which is critical for deep-hole drilling where heat buildup is the #1 killer of bits.

If you are drilling deep holes (more than 3x the diameter of the bit), the polished flutes of a Ground (HSS-G) bit are essential. They pull waste out so efficiently that the bit stays cool. If you use a Rolled (HSS-R) bit for deep holes, the rougher flutes can 'clog,' causing the bit to overheat and lose its temper (hardness) instantly.

Concentricity (The "Wobble" Factor)

Because Ground bits are machined from a single centered axis on a lathe, they have near-perfect concentricity.

Rolled bits can sometimes be a fraction of a millimeter "off-center" due to the heat and twisting process.
The Result: If you use a Rolled bit in a high-precision drill press, you might notice a tiny "wobble" at the tip. For a Ground bit, the tip should stay perfectly still as it spins.

Which one do you need?

Choose Rolled (HSS-R) if:

You are doing general home maintenance or DIY.
You are drilling into soft materials like wood, plastic, or mild steel.
You use a handheld drill (where you might not stay perfectly straight).
You want a "disposable" bit for rough jobs where damage is likely.

Choose Ground (HSS-G) if:

You are an engineer or professional who needs exact hole tolerances.
You are using a drill press or stationary setup.
You are drilling into tougher metals (alloyed steel or cast iron).
You want the cleanest possible hole with minimal burrs or cleanup.

Frequently Asked Questions

Q: Can I use ground bits for wood?

A: Yes, they will cut wood very cleanly. However, because wood is soft, you usually don't need the precision (or the price tag) of a ground bit.

Q: Why are rolled bits usually black?

A: They are typically finished with a steam oxide coating. This helps with heat resistance and prevents the bit from "welding" to the material, but it's also a byproduct of the rolling process.

Q: Is a black drill bit for wood or metal?

A: "Black" usually refers to a Black Oxide coating, which is a finish applied to High-Speed Steel (HSS) bits. Because this coating is common on two very different types of bits:

Brad Point Drill Bit: If the black bit has a sharp, needle-like point in the center and two "ears" (spurs) on the outside, it is a Brad Point bit, which is exclusively for woodwork applications.
Standard Twist DriIl Bit: the black bit has a angled, V-shaped tip (like a tiny mountain peak) with no sharp center needle, it is a standard Jobber Twist Bit, which is primarily for metalwork but can be also used in various applications (including woodwork).

If you find a black bit that looks like a standard twist bit but is labelled "HSS-R", it's the ultimate "beater" bit. Use it for rough construction where you might hit a nail in wood—it's tough enough to handle the metal but cheap enough that you won't mind if it gets thrashed.

Q: Is HSS-G the same as Cobalt?

A: No. HSS-G refers to how the bit is shaped (ground). Cobalt refers to the coating applied/material it is made of. You can find both rolled and ground bits in different steel alloys, though high-end alloys like Cobalt are almost always ground.