Meet the Thread & Fastener Chart — Tap Drill
Look up metric (M1.6–M36, coarse and fine) and imperial UNC/UNF threads: tap drill, clearance holes (ISO 273), socket-head counterbore.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
Illustration. Open the tool for the real thing.
See it in action
The Thread & Fastener Chart — Tap Drill with sample data entered and the result showing.
What is the Thread & Fastener Chart — Tap Drill?
Every mechanical design needs the same handful of numbers over and over: the tap drill for a thread, the clearance hole for a bolt, the counterbore for a socket-head cap screw. This lookup gives them for metric threads M1.6 to M36 in coarse and fine pitch, with the minor and pitch diameters, the tensile stress area, the ISO 273 close/normal/loose clearance holes, ISO 4762 cap-screw head size and hex key, DIN 974 counterbore and depth, ISO 10642 countersunk head diameter and ISO 4032 nut size across flats.
Choose a property class (4.6, 8.8, 10.9, 12.9 or A2-70) and it estimates the preload at 70% of proof load and a tightening torque with the textbook K = 0.2 nut factor. A second tab lists the imperial UNC/UNF sizes from #2-56 to 1-8 with major diameter, TPI, pitch and the tap drill and clearance drill. For 3D-printed holes, add 0.2 mm to the normal clearance size.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
Coarse and fine pitches with pitch/minor diameters and stress area.
Tap drill, ISO 273 clearance (fine/normal/loose) and 3D-printed clearance.
Cap-screw head, hex key, counterbore, countersink and nut dimensions.
#2-56 to 1-8 with tap and clearance drills.
AZRS tools are free to open and use.
It opens in your browser, so there is nothing to download.
Used for
Pick one to see how it fits.
How it compares
A plain look at this tool next to the usual alternative.
| This engineering calculator | Desktop software | |
|---|---|---|
| Install | Nothing to install | Usually an app or program to install |
| Account | No signup | Depends on the product |
| Cost | Free to use | Free or paid, depends on the product |
| Where it runs | In your browser tab | On your computer |
Questions people ask
How is tap drill calculated?
Drill ≈ major diameter − pitch, which gives about 75% thread engagement.
Which standard for clearance holes?
ISO 273 close, medium and coarse series.
Are torque numbers exact?
No — they are a typical rule of thumb for dry steel threads (K = 0.2).
Does it include BSP/NPT?
Not currently — metric and unified (UNC/UNF) only.
How do I use the Thread & Fastener Chart — Tap Drill?
1. Choose a metric thread and pitch (or the imperial tab). 2. Read the tap drill and clearance hole. 3. Check head, counterbore and nut dimensions. 4. Use the preload and torque guidance for the property class.
More free tools
Related to the Thread & Fastener Chart — Tap Drill.
Try the Thread & Fastener Chart — Tap Drill now
Metric & imperial thread data: tap drill, clearance holes, head sizes, torque. Free to use.
Try it free