M20 × 2.5 Tap Drill Size & Thread Specs
Everything for a M20 × 2.5 coarse pitch thread on one page: tap drill (17.5 mm), clearance holes, wrench and hex key sizes, and the nearest inch thread.
SP-TD-01 · M20 × 2.5
M20 × 2.5 specs
SizePlate
M20 × 2.5 · tap with
17.5 mm drill
.6890″
17.5 mm · 77% thread
- Inch drill
- 11/16 · .6875
- Clearance
- 21 / 22 mm
- Wrench
- 30 mm
- Cap screw key
- 17 mm
Thread
- Nominal size
- M20 · .7874″
- Pitch
- 2.5 mm · 10.2 TPI
- Series
- coarse
- fine pitch
- M20 × 1.5
Drilling
- Tap drill
- 17.5 mm · .6890
- Inch substitute
- 11/16 · .6875
- Close fit
- 21 mm
- Normal fit
- 22 mm
- Free fit
- 24 mm
Tools
- Hex head (ISO 4017)
- 30 mm
- Hex head (DIN 933)
- 30 mm
- Socket head cap key
- 17 mm
- Button head key
- —
- Flat head key
- —
Nearest inch
- Thread
- 3/4-10
- Major diameter
- .7500″
- Threads per inch
- 10
- Tap drill
- 21/32
- Interchangeable
- No
Not interchangeable means the threads look close but won't run together: forcing one into the other strips both.
Drill size by thread percentage
Larger drill, less thread, easier tapping. 75% is the usual target.
| Drill | Decimal | mm | Thread |
|---|---|---|---|
| 11/16 | .6875 | 17.46 | 78% |
| 17.5 mm | .6890 | 17.5 | 77% |
| 45/64 | .7031 | 17.86 | 66% |
| 18 mm | .7087 | 18 | 62% |
| 23/32 | .7188 | 18.26 | 54% |
| 18.5 mm | .7283 | 18.5 | 46% |
Neighboring sizes
- M14 × 1.5tap 12.5 mm
- M16 × 2.0tap 14 mm
- M16 × 1.5tap 14.5 mm
- M20 × 1.5tap 18.5 mm
- M24 × 3.0tap 21 mm
- M24 × 2.0tap 22 mm
Questions
What does M20 × 2.5 mean?
An ISO metric thread with a 20 mm major diameter and a 2.5 mm pitch (the distance from one thread crest to the next). It’s the coarse pitch for M20.
Can I use a 11/16 drill instead?
Usually. 11/16 is .6875″ against .6890″ for the 17.5 mm drill, which changes the thread engagement by a few percent at most.