What Are Jobber Length Drill Bits?
Jobber length drill bits are general-purpose twist drill bits with a standard length-to-diameter proportion designed to provide a balance of drilling depth, reach, and rigidity. They are one of the most commonly used drill bit configurations for metalworking, fabrication, maintenance, repair, manufacturing, and general shop drilling.
The term jobber length refers to the drill bit's overall length and flute-length configuration rather than its diameter or cutting material. Jobber drill bits are longer than shorter-length styles such as mechanic length drills, but shorter than extended-length drill bits designed for deep or difficult-to-reach holes.
What Does Jobber Length Mean?
"Jobber length" describes a standard general-purpose drill length. The exact overall length and flute length vary with the diameter of the drill bit, so jobber length does not refer to one fixed physical length.
The proportions provide enough flute length for many everyday drilling applications while maintaining greater rigidity than significantly longer drill bits. This makes jobber length drills a versatile choice when neither an especially short nor an extended-reach drill bit is required.
What Are Jobber Drill Bits Used For?
Jobber drill bits are commonly used for drilling holes in metal and other compatible materials. Their general-purpose dimensions make them useful for both portable drilling and machine-shop applications.
- Metal fabrication and sheet metal work
- Machine shops and production drilling
- Equipment maintenance and repair
- Automotive and mechanical work
- Manufacturing and OEM assembly
- Fastener clearance holes
- Pilot holes for tapping
- General workshop drilling
Jobber length vs. mechanic length drill bit guide comparing reach, rigidity, working clearance, and typical metal drilling applications.
Jobber Length vs. Mechanic Length Drill Bits
The primary difference between jobber length and mechanic length drill bits is the length of the drill. Jobber length bits provide additional reach and drilling depth, while mechanic length bits use a shorter overall length and shorter flutes.
| Feature | Jobber Length Drill Bits | Mechanic Length Drill Bits |
|---|---|---|
| Overall Design | Standard general-purpose length | Shorter, more compact length |
| Reach | Greater reach and drilling depth | Reduced reach |
| Rigidity | Good general-purpose rigidity | Greater rigidity due to shorter length |
| Best For | General drilling and everyday shop work | Tight spaces and applications where added rigidity is preferred |
Choose a jobber length drill bit when you need a versatile balance between reach and rigidity. Choose a mechanic length drill bit when access is limited or the shorter drill configuration is better suited to the application.
HSS Jobber Length Drill Bits
High-speed steel (HSS) jobber drill bits are a versatile choice for general drilling applications. HSS provides a combination of toughness, cutting performance, and heat resistance suitable for drilling many common metals when the correct speed, feed, and cutting lubricant are used.
HSS jobber drills are commonly used for fabrication, maintenance, repair, production work, and general-purpose drilling where a standard-length twist drill is required.
Cobalt Jobber Length Drill Bits
Cobalt jobber drill bits are designed for demanding metal-drilling applications where increased heat resistance and cutting-edge durability are beneficial. They are commonly selected for harder materials and applications that generate more heat during drilling.
Cobalt drill bits can be particularly useful when drilling stainless steel and other difficult-to-machine metals. Proper drilling speed, steady feed pressure, and suitable cutting fluid are important for achieving good performance and extending drill-bit life.
Fractional, Number & Letter Jobber Drill Bits
Jobber length drill bits are available in multiple sizing systems to provide the hole diameter required for general drilling, fastener installation, clearance holes, and tap-drill applications.
Fractional Jobber Drill Bits
Fractional jobber drill bits use common inch-based fractional diameters. They are widely used for fabrication, maintenance, construction, repair, and general drilling applications.
Number Jobber Drill Bits
Number-size jobber drill bits provide closely spaced diameters identified by drill numbers. These sizes are useful for machining, precision hole sizing, clearance holes, and preparing holes for tapping.
Letter Jobber Drill Bits
Letter-size jobber drill bits use sizes A through Z and provide additional diameters between many common fractional sizes. They are frequently used in machining, fabrication, and tap-drill applications requiring a specific hole diameter.
How to Choose a Jobber Length Drill Bit
Choose the drill bit based on the workpiece material, required hole diameter, drilling depth, drill material, and application. The correct combination will depend on what you are drilling and the finished hole requirements.
- Diameter: Select the exact hole size required for the fastener, clearance hole, or tapped thread.
- Sizing system: Choose fractional, number, or letter sizes depending on the required diameter.
- Drill material: Select HSS, cobalt, or another available drill material appropriate for the workpiece.
- Hole depth: Confirm that the jobber length provides sufficient flute and overall length for the required hole.
- Workpiece material: Match the drill-bit construction and cutting geometry to the metal or other material being drilled.
Jobber Drill Bits for Stainless Steel
When drilling stainless steel, choose a drill bit suitable for the specific stainless grade and application. Cobalt jobber drill bits are commonly selected for stainless steel because of their ability to maintain cutting performance at the elevated temperatures generated during metal drilling.
Use a slower drilling speed, firm and consistent feed pressure, and an appropriate cutting fluid. Excessive speed or insufficient feed can generate heat without allowing the cutting edges to remove material efficiently.
Jobber Drill Bits for Tap Holes
Jobber length drills are commonly used to prepare holes before cutting internal threads with a tap. The correct tap drill size depends on the thread diameter and thread pitch being created.
Number and letter jobber drills are particularly useful for tapping because many recommended tap-drill diameters fall between common fractional drill sizes. Always select the specified tap-drill diameter for the thread being produced.
Tips for Drilling Metal With Jobber Drill Bits
- Center punch the workpiece where appropriate to help prevent the drill from walking when starting the hole.
- Secure the material before drilling to prevent movement.
- Use the correct drilling speed for the drill diameter and workpiece material.
- Apply steady feed pressure so the cutting edges continue removing material.
- Use appropriate cutting fluid when drilling metals where lubrication and cooling are recommended.
- Clear chips during deeper drilling to reduce heat and prevent chip buildup in the flutes.
- Replace or sharpen dull drill bits rather than increasing pressure to compensate for worn cutting edges.
Related Drill Bit Categories
Jobber Length Drill Bits FAQs
What is a jobber length drill bit?
A jobber length drill bit is a general-purpose twist drill with a standard length-to-diameter proportion that provides a balance of drilling depth, reach, and rigidity. Jobber length is one of the most commonly used drill configurations for everyday drilling applications.
Why are they called jobber drill bits?
The term "jobber" is traditionally used to describe this common general-purpose drill length. Today, jobber length identifies a standard drill configuration rather than a particular material, diameter, or application.
Are jobber drill bits for metal?
Yes. Jobber length twist drill bits are widely used for drilling metal. The appropriate drill material and cutting geometry should be selected for the particular metal being drilled.
What is the difference between jobber and mechanic length drill bits?
Mechanic length drill bits are shorter than jobber length bits. Their shorter construction provides increased rigidity and can make them useful in confined spaces. Jobber length bits provide additional reach and drilling depth for general-purpose applications.
Are jobber drill bits good for stainless steel?
Jobber length drill bits can be used for stainless steel when the drill construction is appropriate for the material. Cobalt jobber drill bits are commonly selected for stainless and other demanding metal-drilling applications because of their heat resistance.
What sizes do jobber drill bits come in?
Jobber length drill bits are available in a wide range of diameters, including fractional inch, number, letter, and other sizing systems depending on the drill series.
Can jobber drill bits be used for tapping?
Yes. Jobber drill bits are commonly used to create pilot holes before tapping internal threads. Use the specified tap-drill diameter for the thread size and pitch being produced.
What is the difference between a jobber drill bit and a regular drill bit?
"Jobber" describes the length configuration of the drill bit. Many drill bits commonly considered standard or general-purpose twist drills are jobber length. Other drill lengths are available when an application requires greater rigidity, shorter access, or extended reach.
Should I choose HSS or cobalt jobber drill bits?
HSS jobber drill bits are versatile for general-purpose drilling in compatible materials. Cobalt jobber drill bits provide increased heat resistance and are commonly selected for harder and more demanding metals, including stainless steel.