Tap Drill Size Chart

M30 x 3.5 Tap Drill Size

Tap drill

26.5 mm 1.0433 in

Use a 26.5 mm drill (1.0433 in) for 77.0% thread.

Fine thread M30 x 2? Use 28 mm. (1.1024 in, 77.0% thread)

The drill size for a M30 x 3.5 tap is 26.5 mm (1.0433 in). If you are wondering what size drill bit a M30 x 3.5 tap needs, that is the one: it leaves 77.0% of thread, which is the figure standard tap and drill charts are built around. Below are the other holes you might want for this size - a larger drill for tough material, the form-tap hole, and the clearance holes for the bolt that goes in.

Every drill for M30 x 3.5

Tap drills and clearance drills for M30 x 3.5 (Metric coarse, 3.5 mm pitch). Percent of thread is the figure stored for each drill, which reproduces from the major diameter and pitch of M30 x 3.5.
Use Drill Decimal in mm % thread
Standard tap drill Cut tap, general use (D - P) 26.5 mm 1.0433 26.50 77.0%
Inch substitute Closest inch drill if you have no metric set 1-3/64″ 1.0469 26.59 75.0%
Hard material Stainless, tool steel, anything that fights the tap 27.5 mm 1.0827 27.50 55.0%
Form (roll) tap Theoretical 28.45 mm - starting point, check your tap maker's chart 28.5 mm 1.122 28.50 —

Clearance holes for a M30 x 3.5 bolt

A clearance hole is not tapped. It is the hole in the part the bolt passes through, so it is always larger than the thread.

Clearance holes for M30 x 3.5 per ISO 273. Clearance depends on the bolt diameter alone, so every M30 thread shares these figures.
Fit Hole mm Hole in
Fine 31.00 1.2205
Medium 33.00 1.2992
Coarse 35.00 1.378

M30 x 3.5 dimensions

Nominal dimensions for M30 x 3.5. The basic internal minor diameter is the hole a 100% thread would start from, which is why no tap drill is ever that small.
Dimension Inch mm
Major diameter 1.1811 30.00
Basic internal minor diameter 1.0319 26.21
Pitch 0.1378 3.50
Thread designation M30 x 3.5

What the hole looks like

Cross-section of a M30 x 3.5 tapped hole, drawn to scale The drilled hole is 26.5 mm, 1.0433 inches or 26.50 millimetres across. The tap cuts outward from that wall to the major diameter of 1.1811 inches. A 100 percent thread would reach in to the basic minor diameter of 1.0319 inches, shown as a dashed line; the difference is why this drill gives 77.0% of thread. major 30 mm drill 26.5 mm · 26.5 mm dashed = 100% thread at 26.21 mm
M30 x 3.5 in section, to scale. The accent line is the thread the tap cuts from a 26.5 mm hole; the dashed line is where the crest would sit at 100% thread. The gap between them is the 23.0% of thread this drill leaves behind.

Work out a different hole for M30 x 3.5

Pre-filled with M30 x 3.5. Change the material, the tap type, or which drills you actually own, and it picks the closest real drill and tells you the percent of thread you end up with. The tables above are the published figures and do not depend on this.

The general-purpose target

Tap type
Drills you have

Best drill you have, cut tap, 70% target

1-1/16″1.0625 in26.99 mm66.3% thread

Theoretical hole 26.82 mm

One size down, deeper thread1-3/64″ 1.0469 in · 75.0%

One size up, easier tapping27 mm 1.063 in · 66.0%

For comparison, the published chart drill for M30 x 3.5 is 26.5 mm at 77.0% thread.

Notes on M30 x 3.5

Coarse pitch
M30 x 3.5 is the coarse pitch at 30 mm. It is the usual choice for general work, and it tolerates a slightly off-size hole better than the finer pitches do. Finer options at the same diameter: M30 x 2, M30 x 1.5.
What the standard drill gives you
26.5 mm leaves 77.0% of thread (D - P). That is in the normal 65-80% band most shop charts aim for.
Stainless, tool steel and other tough material
27.5 mm opens the hole to 55.0% engagement. Less material for the tap to cut means less torque and less heat, at the cost of some thread depth.
Using a form (roll) tap
A form tap displaces metal instead of cutting it, so it needs a larger hole: 28.5 mm, against a theoretical 28.45 mm. Treat that as a starting point and check your tap maker's chart.
Closest inch size
1-1/8-7 is the nearest inch thread by diameter (28.58 mm against 30 mm). It is a planning reference only. The two are not interchangeable: the pitches differ, and a bolt from one will not run into a hole tapped for the other.

Related sizes

Same diameter, different pitch

Next size up and down

Closest inch size

1-1/8-7 63/64″ · 0.9844 in · 25.00 mm · 75.8% 28.58 mm major against 30 mm

Not interchangeable. 1-1/8-7 is the nearest size by diameter, nothing more. The pitches differ, so a 1-1/8-7 fastener will not run into a M30 x 3.5 hole and forcing one will strip both.

Guides for tapping M30 x 3.5

Longer reads on the decisions behind the numbers above.

All guides →

M30 x 3.5 tap drill: common questions

What size drill bit do I need for a M30 x 3.5 tap?
A 26.5 mm drill, 1.0433 in. That leaves 77.0% of thread, which is the standard chart figure for M30 x 3.5.
What is the drill size for a M30 x 3.5 tap in inches?
The 26.5 mm tap drill measures 1.0433 in. If you only have inch drills, 1-3/64 in (1.0469 in) is the closest, giving 75.0% thread.
What drill should I use for M30 x 3.5 in stainless steel?
Use 27.5 mm instead of 26.5 mm. It leaves 55.0% of thread rather than 77.0%, so there is less material for the tap to cut and less chance of snapping it.
Is M30 x 3.5 the same as M30 x 2?
No. Both are 30 mm threads, but the pitch differs, so the drills differ: 26.5 mm for M30 x 3.5 and 28 mm for M30 x 2. The taps and the fasteners are not interchangeable.
What is the clearance hole for an M30 x 3.5 bolt?
For a medium fit, 33 mm per ISO 273. A clearance hole is not tapped; the bolt passes straight through it.
A 4 × 6 in card with the drills for this size.