Difference Between Jobber and Mechanics Drill Bits

When choosing a twist drill bit, the most significant distinction usually lies in its length. Jobber bits are the standard workhorses, ideal for general use, while mechanics’ bits—also known as stubby bits—are designed for greater strength and fit into tighter spaces. It's important to understand the balance between reach and rigidity to prevent bit breakage and ensure accurate hole drilling.

Jobber Drill Bits

Nowadays, most fabricators widely utilize the jobber drill bits. They are defined by their length in contrast to their diameter.

A jobber drill's length typically ranges from 8 to 12 times the bit's diameter. This long flute and overall length are advantageous because they allow for:

• Deep Hole Drilling: They can reach through thick material or deep into a workpiece.
• Effective Chip Ejection: The long flutes efficiently carry shavings away from the cutting tip, reducing heat buildup in softer materials like wood, composite, or mild steel.

Flexibility and Breakage

While versatile, the extended length of a jobber bit is its weakness. Because the bit is longer, it is less rigid. When drilling into hard materials or if side pressure is applied, the bit is prone to flexing or "walking." This flexing dramatically increases the chance of the bit shearing or snapping at the entry point, especially with smaller diameters.

Jobber bits are available in the most comprehensive range of size systems, including fractional (1/64 inch to 1 inch), numbered (1 through 80), and lettered (A through Z) sizes.

Mechanics Drill Bit

Mechanics Drills (also often called Stubby Drills) are engineered for maximum strength. They feature both a shorter flute length and a shorter overall length compared to standard Jobber Drills. The increased rigidity prevents the bit from flexing or walking under heavy load, making them suitable for:

• Hard Metal Drilling: Ideal for use on tough materials like high-strength steel (HSS) and stainless steel, where maximum force and rigidity are required.
• Confined Spaces: The short overall length allows them to fit easily into tight engine bays or between auto body panels, where a standard jobber bit would be too long.

When to Choose Which Bit

Selecting the right bit is a balance between the depth of the hole you need and the hardness of the material you are drilling.

Choose a Jobber Bit when:

• The material is soft or mild (wood, aluminum, brass).
• You are using a stable drill press where alignment is guaranteed.

Choose a Mechanics Bit when:

• The material is hard (stainless steel, tool steel).
• You are working in a confined space (e.g., auto repair).
• You are using a handheld drill, which provides less control and requires a more rigid bit to prevent breakage.
• The required hole depth is shallow.