You've lined up your drill bit, applied pressure, and started the motor — but the bit just spins without cutting. Sometimes it smokes, sometimes it vibrates, but it simply won't go in. Understanding why a twist drill fails to bite into the workpiece is the first step toward solving the problem and getting back to efficient drilling.

Dull or Worn Drill Bit

The most common reason a drill bit won't cut is that it's simply dull. When a drill bit is sharp, its cutting edges bite into the material. When the bit becomes dull — from use, overheating, or being used on materials harder than it's designed for — the cutting edges round over and just rub against the workpiece instead of cutting.

Specific signs:

• The bit spins but produces only fine dust or nothing at all

• Excessive heat and smoke without progress

• The drill bit tip looks rounded or shiny instead of sharp

Why this happens: Standard high-speed steel (HSS) drill bits lose their hardness when overheated. Once the cutting edge reaches a certain temperature, the metal softens and can no longer hold a sharp edge.

Incorrect Drill Bit Geometry

A drill bit's cutting geometry is critical for proper function. If the bit is sharpened incorrectly, it simply won't cut effectively.

Common geometry problems:

Poor Initial Positioning

On smooth, curved, or hard surfaces, the drill bit's tip can "walk" — skidding sideways across the surface instead of biting in. If the bit can't establish a starting point, it will never begin cutting. This is especially common on stainless steel, tubing, and round surfaces.

Solutions:

• Use a center punch to create a dimple that guides the bit

• Start with a smaller bit (spotting drill) to create a pilot hole

• Use a center drill first to establish a starting point

• Drill at a lower speed until the bit bites, then increase speed

Incorrect Speed and Feed

Even a perfectly sharp drill bit won't cut if the speed and feed are wrong.

Speed too high: When the drill bit spins too fast, it can overheat instantly, softening the cutting edges before they ever bite into the material. This is especially common when drilling stainless steel or hard metals with a hand drill.

Speed too low: Excessively low speed can prevent the cutting edges from engaging properly, especially with small-diameter bits.

Feed pressure too light: If you don't apply enough downward pressure, the bit will just spin without the cutting edges biting into the material. This is particularly true for materials that work-harden.

Feed pressure too heavy: Excessive pressure can cause the bit to bind, overheat, or break, especially with small bits.

Different Workpiece Materials

Some materials are naturally difficult to drill and require special handling.

Stainless steel and work-hardening materials: Stainless steel work-hardens as it gets hot. If the drill bit rubs instead of cuts — due to dullness, incorrect speed, or insufficient pressure — the material surface becomes harder than the drill bit itself. Once this happens, the bit can no longer penetrate.

Hardened steel: Standard HSS bits cannot cut hardened steel. Attempting to do so will just dull or break the bit.

Cast iron: The powdery chips can clog the flutes and cause the bit to bind.

Soft, gummy materials (aluminum, copper, low-carbon steel): These materials can build up on the cutting edges, preventing the bit from cutting effectively.

Uneven Workpiece Surface, Porosity, or Sand Inclusions

Even a perfectly sharp and correctly sharpened drill bit can fail to cut if the workpiece surface is uneven or contains defects.

When the workpiece surface is not flat — curved, sloped, or irregular — the drill bit tip contacts the surface at an angle rather than straight on. This causes the bit to walk or skate instead of biting in. The uneven surface provides no stable point for the drill to establish a starting dimple.

Cast materials often contain small voids (porosity) or hard particles (sand inclusions). When the drill bit hits a void, it loses its cutting resistance and can suddenly grab when it exits the void. When it hits a hard sand inclusion, the cutting edge can chip or break immediately.

How to fix:

For uneven surfaces: File or grind a small flat spot before drilling; use a center punch to create a deep starting dimple; start with a very short, stiff spotting drill

For castings: Use a carbide drill bit that can handle hard inclusions; reduce speed and increase feed pressure; use a stub-length drill for better rigidity

For mill scale: Remove scale with a grinder or abrasive wheel before drilling; start with a spotting drill to get through the hard surface layer