The tap drill for M5 x 0.8 is 4.2 mm (0.1654 in), which gives about 77% of full thread depth. The exact 75% hole is 0.1662 in (4.22 mm). The table lists every number, letter, fractional and metric drill that gives between 55% and 90% thread, so you can work from the bits you own.
| Drill | Type | in | mm | Thread | Note |
|---|---|---|---|---|---|
| #20 | number | 0.1610 | 4.09 | 88% | deep, hard to tap |
| 4.1 mm | metric | 0.1614 | 4.10 | 87% | deep, hard to tap |
| 4.2 mm | metric | 0.1654 | 4.20 | 77% | chart drill |
| #19 | number | 0.1660 | 4.22 | 75% | |
| 4.3 mm | metric | 0.1693 | 4.30 | 67% | easier to tap |
| #18 | number | 0.1695 | 4.31 | 67% | easier to tap |
| 11/64" | fraction | 0.1719 | 4.37 | 61% | easier to tap |
| #17 | number | 0.1730 | 4.39 | 58% | easier to tap |
| 4.4 mm | metric | 0.1732 | 4.40 | 58% | easier to tap |
About the M5 x 0.8 thread
M5 x 0.8 is the thread for bicycle bottle cages and many bike accessory bosses, as well as small brackets, motor mounts, pneumatic fittings and electronics racks. On a bike frame it is often in a thin rivnut, which is why stripped bottle-cage bolts are such a common repair.
Diameter minus pitch gives 4.2 mm, which is the chart drill and close to the 75% target. M5 sits between the two #10 inch threads in diameter, so an M5 bolt in a 10-24 or 10-32 hole is a frequent mistake.
M5 x 0.8 thread dimensions
| Dimension | Value | Also |
|---|---|---|
| Nominal diameter | 5 mm | 0.1969 in |
| Pitch | 0.8 mm | 31.75 threads per inch equivalent |
| Basic pitch diameter | 4.480 mm | 0.1764 in |
| Basic minor diameter (nut) | 4.134 mm | 0.1628 in |
| Tensile stress area | 14.18 mm² | 0.0220 in² |
Clearance hole for M5
The tapped hole is in the part that holds the thread; the part being clamped gets a clearance hole the bolt passes through. For M5 a normal fit is 5.5 mm. Never drill the clearance part with the tap drill: the screw will not pass.
| Fit | Drill | Diameter |
|---|---|---|
| Close (ISO 273 fine) | 5.3 mm | 0.2087 in |
| Normal (ISO 273 medium) | 5.5 mm | 0.2165 in |
| Loose (ISO 273 coarse) | 5.8 mm | 0.2283 in |
How deep to drill a blind M5 x 0.8 hole
| Part material | Full thread wanted | Drill depth (full diameter) | Depth to drill tip (118°) |
|---|---|---|---|
| Steel or cast iron (1 × diameter) | 5.0 mm | 10.6 mm | 11.9 mm |
| Aluminium or brass (2 × diameter) | 10.0 mm | 15.6 mm | 16.9 mm |
Wrench size and torque for M5
- Hex bolt or nut: 8 mm wrench (ISO)
- Socket head cap screw (ISO 4762): 4 mm hex key
| Bolt grade | Dry | Lubricated |
|---|---|---|
| Class 8.8 | 6.2 N·m (4.6 ft-lb) | 4.6 N·m |
| Class 10.9 | 8.8 N·m (6.5 ft-lb) | 6.6 N·m |
| Class 12.9 | 10.3 N·m (7.6 ft-lb) | 7.7 N·m |
Threads easily mistaken for M5 x 0.8
| Thread | Diameter (in) | Diameter (mm) | Pitch |
|---|---|---|---|
| M5 x 0.8 (this page) | 0.1969 | 5.00 | 0.8 mm (31.7 TPI) |
| #10-24 UNC | 0.1900 | 4.83 | 24 TPI (1.06 mm) |
| #10-32 UNF | 0.1900 | 4.83 | 32 TPI (0.79 mm) |
Tips for tapping M5 x 0.8
- Bottle-cage bosses: the thread is usually in a thin rivnut; tighten gently and to the frame maker’s figure, as an over-tightened rivnut can spin in the frame.
- An M5 socket head cap screw takes a 4 mm hex key; an M5 hex bolt needs an 8 mm wrench.
- In soft aluminium, 10 mm of thread engagement gives a margin over a steel screw.
- Drill the hole square: a small M5 tap that starts at an angle is easily broken on the third or fourth turn.
Frequently asked questions
What size drill bit for an M5 x 0.8 tap?
4.2 mm, which gives about 77% thread. The exact 75% size is 0.1662 in (4.22 mm).
How deep should a blind M5 x 0.8 hole be?
For a full thread of 1 × diameter in steel, drill about 10.6 mm at full diameter with a plug tap, or 11.9 mm to the drill tip; in aluminium, about 15.6 mm.
Is M5 the same as 10-32?
No. M5 is 0.197 in in diameter with 0.8 mm pitch; 10-32 is 0.190 in with 0.794 mm pitch. The pitches are nearly the same, so an M5 screw can start in a 10-32 hole and then bind as the diameter difference takes over.
What size drill for an M5 tap in inches?
#19 (0.166 in, 4.22 mm) is the closest; 11/64 in (4.37 mm) gives a shallower thread.
Sources and method
Every dimension and percentage on this page is computed from the formulas listed, not copied from another chart. Values are basic (nominal); real parts are made to tolerance classes (2A/2B for inch, 6g/6H for metric).
- ASME B1.1 and FED-STD-H28/2B (Unified inch), ISO 68-1 and ISO 261 (metric): basic thread profile and stress area formulas.
- Machinery’s Handbook (Industrial Press): percentage-of-thread relation used by our tap drill size calculator.
- ASME B94.11M twist drill series (number, letter, fractional); 0.1 mm metric drill steps.
- ISO 273 metric clearance holes; inch close, normal and loose fits as published in the ASME B18.2.8 clearance classes.
- SAE J429 and ISO 898-1 proof strengths; T = K × D × F torque relation (see our bolt torque chart for the full method).
- Wrench and hex key sizes: ASME B18.2.1, ASME B18.3, ASME B18.6.3, ISO 4014/4017, DIN 933 and ISO 4762 values as widely published.
More thread and fastener tools
- All thread and fastener charts
- UNC and UNF thread chart
- Metric thread pitch chart
- Tap drill chart (inch and metric)
- Clearance hole chart
- Nail size chart
- Wood screw size chart
- Lag screw pilot hole chart
- Bolt torque chart
- Wrench size chart
- Drill bit size chart
- Thread engagement chart
- Nail gun nail sizes by gauge
- Screw and nail size calculator
- Tap drill size calculator
- Clearance hole size calculator
- Tapped hole depth calculator
Last reviewed: 24 October 2026. How we build and check our data: methodology and corrections. Spotted an error? Please let us know.