When it comes to threading, few tools are as essential as taps and dies. Whether you’re working in automotive repair, mechanical engineering, metal fabrication, or even DIY home projects, understanding how to properly use a tap and die drill chart can save you a lot of time and frustration.
This guide will break down everything you need to know about taps, dies, drill sizes, and the charts that connect them. By the end, you’ll not only understand how to read a tap and die chart but also how to apply it effectively in real-world scenarios.
What Are Taps and Dies?
Before diving into charts, it’s important to understand the tools themselves.
Tap: A tap is used to cut internal threads inside a drilled hole. These threads allow bolts or screws to fasten securely.
Die: A die is used to cut external threads, such as those on a bolt or threaded rod.
Both tools are precision-designed to ensure consistent threading, making them indispensable in metalworking and mechanical repairs.
Why Do You Need a Tap and Die Drill Chart?
When threading a hole with a tap, you can’t just pick any random drill bit size. The hole must be drilled to a specific size that allows the tap to cut threads without breaking or creating weak, shallow threads.
This is where a tap and die drill chart comes in. It provides a quick reference for:
Correct drill size for tapping holes.
Corresponding tap size for specific threads.
Thread pitch and counts for metric and imperial systems.
Without using the correct chart, you risk broken taps, damaged dies, and poorly threaded holes.
How to Read a Tap and Die Drill Chart
A standard chart contains:
Tap Size: The nominal size of the tap, e.g., M6 or 1/4″-20.
Thread Pitch or TPI (Threads per Inch): Distance between threads (metric) or number of threads in one inch (imperial).
Drill Size: The size of the drill bit you need to use before tapping.
For example:
Tap: M6 x 1.0
Pitch: 1.0 mm
Drill Size: 5.0 mm
This means you must drill a 5.0 mm hole before threading it with an M6 x 1.0 tap.
Tap and Die Drill Chart (Metric Sizes)
Here’s a reference table for commonly used metric taps and drill sizes.
| Metric Tap Size | Thread Pitch (mm) | Drill Size (mm) |
|---|---|---|
| M3 x 0.5 | 0.5 | 2.5 |
| M4 x 0.7 | 0.7 | 3.3 |
| M5 x 0.8 | 0.8 | 4.2 |
| M6 x 1.0 | 1.0 | 5.0 |
| M8 x 1.25 | 1.25 | 6.8 |
| M10 x 1.5 | 1.5 | 8.5 |
| M12 x 1.75 | 1.75 | 10.2 |
| M16 x 2.0 | 2.0 | 14.0 |
Tap and Die Drill Chart (Imperial Sizes)
Imperial taps use threads per inch (TPI) instead of metric pitch.
| Tap Size | TPI | Drill Size (Inches) | Drill Size (mm) |
|---|---|---|---|
| 1/4″-20 UNC | 20 | 0.201″ (#7 drill) | 5.1 mm |
| 5/16″-18 UNC | 18 | 0.257″ (F drill) | 6.5 mm |
| 3/8″-16 UNC | 16 | 0.3125″ (5/16 drill) | 7.9 mm |
| 7/16″-14 UNC | 14 | 0.368″ (U drill) | 9.4 mm |
| 1/2″-13 UNC | 13 | 0.421″ (27/64 drill) | 10.7 mm |
| 5/8″-11 UNC | 11 | 0.531″ (17/32 drill) | 13.5 mm |
Tap and Die Drill Chart PDF
Our Tap and Die Drill Chart PDF is a handy reference for machinists, mechanics, and DIY enthusiasts. It includes both metric and imperial tap sizes with matching drill sizes, ensuring accurate threading every time. Download this chart to save time, reduce errors, and make your tapping projects smoother and more reliable.
Also Read:
Differences Between Metric and Imperial Charts
Measurement System:
Metric uses millimeters.
Imperial uses inches and drill gauge numbers.
Thread Description:
Metric: Pitch in millimeters (distance between threads).
Imperial: Threads per inch (TPI).
Common Usage:
Metric is more common worldwide.
Imperial is widely used in the U.S. and older machinery.
How to Select the Right Drill Size
Choosing the correct drill size is crucial for successful tapping:
Undersized Hole:
Too small, tap may break due to high resistance.
Oversized Hole:
Threads will be shallow, weak, and unable to hold a fastener securely.
Correct Hole:
Matches the chart, allowing smooth threading and strong results.
Step-by-Step Process to Use a Tap and Die
For Tapping a Hole:
Select the correct drill size using the chart.
Drill the hole perpendicular to the surface.
Apply cutting fluid for lubrication.
Insert the tap and turn clockwise, backing off every half-turn to clear chips.
Continue until the full depth is threaded.
For Threading with a Die:
Secure the rod or bolt material in a vise.
Place the die in the die stock handle.
Lubricate the surface.
Rotate the die clockwise, backing off occasionally to clear chips.
Continue threading until desired length is reached.
Also Read: Drill Chart: Complete Guide with PDF
Practical Applications of Tap and Die Charts
Automotive: Repairing stripped threads in engine blocks or cylinder heads.
Industrial: Creating custom bolts and threaded rods.
DIY Projects: Fixing furniture, machines, or hobby projects.
Fabrication Shops: Producing precision parts.
Common Mistakes Beginners Make
Ignoring the Chart – leads to broken taps.
Skipping Lubrication – causes heat build-up and tool wear.
Not Clearing Chips – makes threading uneven.
Using Wrong TPI or Pitch – mismatched fasteners won’t fit.
Safety Tips When Using Taps and Dies
Always wear safety glasses.
Use cutting oil to reduce friction.
Don’t force the tap – if it resists, back it out.
Hold workpieces securely in a vise.
Use high-quality tools for accurate results.
Also Read: Metric Tap Drill Chart: Complete Guide
Advanced Notes on Tap Types
Taper Tap: Starts threading gradually; good for beginners.
Plug Tap: Middle-ground option, versatile.
Bottoming Tap: Used for blind holes that need threads near the bottom.
Each requires the same drill size, but the type determines how the thread is cut.
Also Read: Metric Drill and Tap Chart: A Complete Guide
Conclusion
A tap and die drill chart is more than just a reference table — it’s your guarantee for accuracy, durability, and safety in any threading project. Whether you’re working with metric or imperial systems, knowing the correct drill size before tapping ensures your fasteners fit securely every time.
From automotive repair to industrial fabrication, mastering taps, dies, and their charts is an essential skill for anyone dealing with threads. With practice, proper lubrication, and careful attention to detail, you’ll avoid common mistakes and achieve professional-quality results.
FAQs Related To Tap and Drill Sizes:
What drill size do I use for a 1/4-20 tap?
For a 1/4″-20 UNC tap, you need a #7 drill bit (0.201 inches or 5.1 mm). This size ensures the right hole diameter for cutting strong threads. If the hole is too small, the tap may break, and if it’s too large, the threads will be weak. Always check a reliable tap and die drill chart before drilling.
How do I know which tap drill size to use?
The correct tap drill size is determined by the tap’s size and pitch (metric) or threads per inch (imperial). A tap and die drill chart provides a quick reference for pairing taps with the proper drill bits. Using the wrong size can damage your tools or create weak threads. Always check whether your project requires metric or imperial standards before drilling.
What size drill bit do I use for M6 tap?
For an M6 x 1.0 tap, you should use a 5.0 mm drill bit. This is the recommended size for creating a hole that allows the tap to cut threads efficiently without breaking. Using a smaller bit may cause tool failure, while a larger one can result in weak threads. Always verify sizes with a tap drill chart before working.
Can I use a regular drill bit for tapping?
Yes, you can use a regular drill bit, but it must match the size recommended on the tap and die drill chart. The hole size must be precise to ensure the tap cuts threads properly. For example, a 1/4″-20 tap requires a #7 drill bit. Using random drill sizes without referencing a chart may lead to broken taps or poor-quality threads.
What’s the difference between coarse and fine thread taps?
Coarse thread taps have fewer threads per inch (TPI) or a larger pitch in metric sizes, making them stronger and easier to cut. They’re commonly used in general applications like automotive and machinery. Fine thread taps have more threads per inch, offering greater holding power and precision but are harder to tap. A tap and die drill chart usually lists both coarse and fine thread sizes.
Why is lubrication important when using taps and dies?
Lubrication reduces friction and heat, prevents tool wear, and helps remove chips while cutting threads. Without lubrication, taps and dies can bind, break, or produce rough threads. Different materials require specific cutting oils: for steel, use tapping fluid; for aluminum, lightweight oil works best. A well-lubricated tap not only ensures smooth operation but also extends tool life and results in cleaner, stronger threads.