Tap Drill Size Chart

M30 x 1.5 Tap Drill Size

Tap drill

28.5 mm 1.122 in

Use a 28.5 mm drill (1.122 in) for 77.0% thread.

The drill size for a M30 x 1.5 tap is 28.5 mm (1.122 in). If you are wondering what size drill bit a M30 x 1.5 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 1.5

Tap drills and clearance drills for M30 x 1.5 (Metric fine, 1.5 mm pitch). Percent of thread is the figure stored for each drill, which reproduces from the major diameter and pitch of M30 x 1.5.
Use Drill Decimal in mm % thread
Standard tap drill Cut tap, general use (D - P) 28.5 mm 1.122 28.50 77.0%
Inch substitute Closest inch drill if you have no metric set 1-1/8″ 1.125 28.58 73.1%
Hard material Stainless, tool steel, anything that fights the tap 29 mm 1.1417 29.00 51.3%
Form (roll) tap Theoretical 29.34 mm - starting point, check your tap maker's chart 29.5 mm 1.1614 29.50 —

Clearance holes for a M30 x 1.5 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 1.5 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 1.5 dimensions

Nominal dimensions for M30 x 1.5. 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 1.1172 28.38
Pitch 0.0591 1.50
Thread designation M30 x 1.5

What the hole looks like

Cross-section of a M30 x 1.5 tapped hole, drawn to scale The drilled hole is 28.5 mm, 1.122 inches or 28.50 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 1.1172 inches, shown as a dashed line; the difference is why this drill gives 77.0% of thread. major 30 mm drill 28.5 mm · 28.5 mm dashed = 100% thread at 28.38 mm
M30 x 1.5 in section, to scale. The accent line is the thread the tap cuts from a 28.5 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 1.5

Pre-filled with M30 x 1.5. 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

1-1/8″1.125 in28.58 mm73.1% thread

Theoretical hole 28.64 mm

One size down, deeper thread28.5 mm 1.122 in · 77.0%

One size up, easier tapping1-9/64″ 1.1406 in · 52.8%

For comparison, the published chart drill for M30 x 1.5 is 28.5 mm at 77.0% thread.

Notes on M30 x 1.5

Finest pitch at this diameter
M30 x 1.5 is the finest of the standard pitches at 30 mm. Fine threads suit thin walls and joints that see vibration, but the hole size matters more: the window between a weak thread and a broken tap is narrower than on M30 x 3.5.
Not the same as M30 x 3.5
M30 x 3.5 and M30 x 1.5 share a 30 mm major diameter but not a pitch, and they take different drills: 26.5 mm for M30 x 3.5, 28.5 mm for M30 x 1.5. The taps and the fasteners are not interchangeable.
What the standard drill gives you
28.5 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
29 mm opens the hole to 51.3% 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: 29.5 mm, against a theoretical 29.34 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 1.5 hole and forcing one will strip both.

Guides for tapping M30 x 1.5

Longer reads on the decisions behind the numbers above.

All guides →

M30 x 1.5 tap drill: common questions

What size drill bit do I need for a M30 x 1.5 tap?
A 28.5 mm drill, 1.122 in. That leaves 77.0% of thread, which is the standard chart figure for M30 x 1.5.
What is the drill size for a M30 x 1.5 tap in inches?
The 28.5 mm tap drill measures 1.122 in. If you only have inch drills, 1-1/8 in (1.125 in) is the closest, giving 73.1% thread.
What drill should I use for M30 x 1.5 in stainless steel?
Use 29 mm instead of 28.5 mm. It leaves 51.3% 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 1.5 the same as M30 x 3.5?
No. Both are 30 mm threads, but the pitch differs, so the drills differ: 28.5 mm for M30 x 1.5 and 26.5 mm for M30 x 3.5. The taps and the fasteners are not interchangeable.
What is the clearance hole for an M30 x 1.5 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.