Whether you’re a professional machinist, mechanical engineer, or DIY hobbyist, knowing the correct tap drill size is essential for accurate threading. Using the wrong drill size can result in poor thread quality, broken taps, or weak fastener connections.
A tap drill chart provides quick reference information on the correct drill bit size to use for a given tap size and thread pitch. To save you time, we’ve compiled 20+ free printable tap drill charts in PDF format—ready to download, print, and keep at your workstation.
📂 What’s Inside These Free Tap Drill Charts?
| Chart Type | Best For |
|---|---|
| 🟢 Metric Tap Drill Chart | Metric thread sizes and pitches |
| 🔵 Imperial (Inch) Tap Drill Chart | Unified thread standard sizes |
| 🟡 Coarse & Fine Thread Chart | UNC (coarse) and UNF (fine) threads |
| 🟣 Pipe Thread Tap Drill Chart | NPT and BSPT pipe threading |
| 🔴 Machine Screw Tap Drill Chart | Small fastener threading |
| ⚫ Combined Metric/Imperial Chart | Side-by-side quick comparison |
| 🟤 Decimal Equivalent Chart | Converting between inches and mm |
✅ Why Use a Tap Drill Chart?
✔️ Prevents errors – Ensures correct hole size for proper threading
✔️ Saves time – No need for manual calculations
✔️ Improves accuracy – Reduces risk of damaged threads or broken taps
✔️ Versatile – Works for both manual and CNC machining
✔️ Handy for quick reference – Ideal for shop walls, toolboxes, and workbenches
🧾 Common Information Found in a Tap Drill Chart
A typical tap drill chart includes:
- Tap size (metric and/or imperial)
- Thread pitch (distance between threads)
- Recommended drill size
- Decimal equivalent (for conversions)
- Notes for coarse vs. fine threads
🛠️ Who Should Use These Charts?
- ✅ Machinists
- ✅ CNC operators
- ✅ Mechanical engineers
- ✅ Metal fabricators
- ✅ Home workshop hobbyists
- ✅ Students learning machining fundamentals
📥 Download 20+ Free Printable Tap Drill Charts [PDF]
All charts are high‑resolution, print‑ready PDFs. You can print them in A4 or Letter size and laminate them for durability in workshop environments.
👉 Download Tap Drill Charts Here
🧠 Example: Tap Drill Chart Reference (Imperial – UNC)
| Tap Size | Threads Per Inch (TPI) | Drill Size | Decimal (in) |
|---|---|---|---|
| #4-40 | 40 | #43 | 0.0890 |
| #6-32 | 32 | #36 | 0.1065 |
| #8-32 | 32 | #29 | 0.1360 |
| 1/4-20 | 20 | #7 | 0.2010 |
| 3/8-16 | 16 | 5/16″ | 0.3125 |
💡 Tips for Using Tap Drill Charts Effectively
✔️ Keep a laminated copy in your workshop for quick reference
✔️ Always double‑check your tap size before drilling
✔️ Use proper cutting fluid to extend tap life and improve thread quality
✔️ When in doubt, drill slightly smaller to ensure full thread engagement
✔️ Replace worn taps to avoid poor-quality threads
📌 Final Thoughts
A tap drill chart is a must-have for anyone working with threaded holes. It ensures that you always choose the correct drill size for clean, accurate threads—whether you’re doing precision CNC work or basic home repairs.
With these 20+ free printable PDF charts, you’ll have the right reference tool at your fingertips every time you work on a threading project.
🟢 Download your free charts today, print them, and keep them handy in your workshop.
