M6 Tap Drill Size (M6 x 1.0)
ISO metric coarse · 1 mm pitch · ISO 261 / 965-1, class 6H
What size drill bit for a M6 tap?
To scale section of the tapped hole
Drill options % of thread
| Drill | Inch | mm | Thread | 6H |
|---|---|---|---|---|
| #10 | 0.1935 | 4.92 | ✗ | |
| #9 | 0.1960 | 4.98 | ✓ | |
| 5 mmUse | 0.1969 | 5.00 | ✓ | |
| #8 | 0.1990 | 5.06 | ✓ | |
| 5.1 mm | 0.2008 | 5.10 | ✓ | |
| #7 | 0.2010 | 5.11 | ✓ | |
| 13/64" | 0.2031 | 5.16 | ✗ | |
| #6 | 0.2040 | 5.18 | ✗ | |
| 5.2 mm | 0.2047 | 5.20 | ✗ |
By material Aluminum, brass, mild steel: 5 mm (77%) · Stainless, tool steel: 5.1 mm (69%)
75% (orange tick) is the usual target. Hard or gummy metals like stainless are often tapped at 60 to 65% to spare the tap; aluminum, brass and plastic take 75% or a little more. The last column checks the hole against the 6H minor diameter limits (4.92 mm to 5.15 mm).
M6 x 1 ISO 261, 965-1, class 6H
| Major diameter | 6 mm / 0.2362 in |
|---|---|
| Pitch | 1 mm |
| Pitch diameter (basic) | 5.351 mm |
| Minor diameter 6H | 4.917–5.153 mm |
| Thread-forming tap drill | 5.6 mm 0.2205 in |
Clearance hole ISO 273
For a screw that passes through the part. Normal fit is the default; close fit locates the part more accurately but leaves no room for hole position error.
Hole depth rule of thumb
- 6 mmthread length for full strength in steel (1 × D)
- 9 mmin cast iron or brass (1.5 × D), up to 12 mm in aluminum
- +5 mmextra drill depth below the thread for a plug tap (5 pitches), +2 mm with a bottoming tap
Shop notes
For metric coarse threads the rule is simple: tap drill equals diameter minus pitch. For M6 x 1 that is 6 minus 1, a 5.0 mm drill, which gives about 77% thread and sits inside the 6H minor diameter tolerance.
In an inch-only shop, a #9 (0.1960 in, 79%) or a #8 (0.1990 in, 73%) both work. The 13/64 that is usually within reach is a different story: at 5.16 mm it cuts only about 65% thread and leaves the hole above the 6H maximum minor diameter. It will hold in a pinch, but it is the wrong default.
M6 is the cage nut size in most square-hole equipment racks and a common size for body and panel fasteners. Plain "M6" always means the 1 mm coarse pitch; the fine M6 x 0.75 exists but you will rarely meet it outside special hardware.
Not a 1/4-20
M6 and 1/4-20 are close in size and often confused. A 1/4-20 bolt will not start in an M6 hole at all, and an M6 screw in a 1/4-20 hole binds after a turn or two. If one of them refuses to thread, check the other before reaching for a bigger wrench.