Drill Bit Set Sizes Explained: What’s Included & How to Choose
Choosing the right drill bit set shouldn’t feel complicated. With so many different piece counts, size increments, and measurement systems, it’s easy to end up with the wrong range. This guide breaks everything down clearly—helping you understand what each set includes, where it’s used, and how to choose the right kit for drilling metal with confidence.
Why Drill Bit Set Sizes Matter
Drill bit sets are built to give you the sizes you’ll actually use on the job. Whether you’re drilling structural steel, maintaining machinery, or fitting hardware, understanding the size spread in your set helps you choose accurately and avoid buying gaps later. If you compare sets like 19-, 21-, 25- or 29-piece kits, each one serves a different level of versatility depending on your work.
How Drill Bit Sets Are Structured
All drill bit sets follow a similar design philosophy. They include a range of sizes in consistent steps so you can drill accurate holes across multiple materials.
- Piece count – how many sizes are included
- Increment steps – 0.5mm or 1/64” depending on system
- System – metric (mm) or imperial (fractional)
- Application – workshops, installers, engineers, fabricators
This structure ensures you always have the next size you need—especially important when drilling through harder metals.
19-Piece Metric Set (1–10mm in 0.5mm Steps)
View the 19-piece metric set here.
This compact kit covers all essential metal-drilling sizes used by installers, engineers, and contractors. With 0.5mm increments, it’s perfect for precision drilling and controlled enlarging of holes on site.
- Ideal for general metal drilling
- Compact and easy to carry
- Perfect for agricultural and plant machinery repairs
25-Piece Metric Set (1–13mm in 0.5mm Steps)
View the 25-piece metric set here.
If you need full coverage from 1mm up to 13mm, this set delivers complete flexibility. It’s the top choice for engineering workshops, fabricators, and anyone drilling thicker or tougher metals.
- Full metric range in precise 0.5mm increments
- Perfect for stainless steel, structural steel, and heavy plate
- Eliminates the need for separate large drill bit purchases
21-Piece Imperial Set (1/16″–3/8″ in 1/64″ Steps)
View the 21-piece imperial set here.
This set covers all core SAE fractional sizes used in automotive work, machinery repair, and metal fabrication. The 1/64” increments give you fine control when hole precision matters.
- Ideal for mechanics and classic car restorers
- Accurate hole sizing for imperial fasteners
- Compact yet extremely versatile
29-Piece Imperial Set (1/16″–1/2″ in 1/64″ Steps)
View the 29-piece imperial set here.
This is the complete imperial range for professionals who need every fractional size up to 1/2”. It’s widely used in workshops where accuracy and flexibility are essential.
- Full SAE range for workshop use
- Perfect for fabrication and heavy machinery maintenance
- Extremely accurate sizing thanks to 1/64” increments
Image showing the 29 pieces in a the large Imperial drill bit set (1/16″ – 1/2″ x 1/64″)
Metric vs Imperial: Which Should You Choose?
Your choice depends on the machinery, fixings, and measurement system you use daily.
Choose Metric If:
- You work with modern European/UK machinery
- Your bolts and fasteners are mm-based
- You drill aluminium, mild steel, or stainless steel to metric dimensions
Choose Imperial If:
- You maintain American vehicles or equipment
- You work with SAE fractional fasteners
- You restore classic or military machinery
Use these references for accuracy:
Why Increment Steps Make a Difference
Whether you’re enlarging a pilot hole or drilling into tough metals, the step size between bits affects accuracy and speed.
- More control when enlarging holes gradually
- Higher accuracy for fastener-matching
- Lower risk of bit wandering
- Reduced chance of oversizing a hole
Real-World Scenarios: Which Set Fits Your Work?
Stainless Steel Installations
Drilling through stainless on site often requires step-ups and controlled enlarging. The 25-piece metric set offers the flexibility needed for clean results.
Agricultural Machinery Repairs
Farmers need a lightweight set with all core sizes. The 19-piece metric set is ideal.
American Classic Car Restoration
Most vehicle fixings are fractional, making the 29-piece imperial set the best choice.
Workshop Fabrication
Fabricators benefit from the complete spread—either the 25-piece metric or 29-piece imperial set.
When You Should Upgrade to a Larger Set
If you frequently drill pilot holes, enlarge holes in stages, or match fastener sizes, upgrading to a bigger set gives better control. Moving from a 19-piece to a 25-piece metric kit or from a 21-piece to a 29-piece imperial kit ensures you always have the next size you need.
Supporting Your Metal Drilling Silo
If you’re comparing sets or exploring alternatives, our core guide provides a full overview of drilling metal sets:
Read the Metal Drill Bit Set Guide
This “sizes explained” page focuses on piece counts and ranges while reinforcing your overall drill bit set content structure.
Final Tips Before Choosing Your Set
- Select the piece count that matches your day-to-day work
- Stick to the measurement system used by your fasteners
- Upgrade if you frequently need step-ups or pilot holes
- Keep a size chart handy for tapping and accurate drilling
- Use proper lubrication and speed to extend drill bit life
Metal Cutting Paste makes drilling metal easier & prolongs drill bit life
Explore All Drill Bit Set Options
Choose the right set for your work:
All sets are engineered for drilling metal and tested for hardness to ensure professional performance.
