Tap Drill Size Chart

M24 x 3 Tap Drill Size

Tap drill

21 mm 0.8268 in

Use a 21 mm drill (0.8268 in) for 77.0% thread.

Fine thread M24 x 2? Use 22 mm. (0.8661 in, 77.0% thread)

The drill size for a M24 x 3 tap is 21 mm (0.8268 in). If you are wondering what size drill bit a M24 x 3 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 M24 x 3

Tap drills and clearance drills for M24 x 3 (Metric coarse, 3 mm pitch). Percent of thread is the figure stored for each drill, which reproduces from the major diameter and pitch of M24 x 3.
Use Drill Decimal in mm % thread
Standard tap drill Cut tap, general use (D - P) 21 mm 0.8268 21.00 77.0%
Inch substitute Closest inch drill if you have no metric set 53/64″ 0.8281 21.03 76.1%
Hard material Stainless, tool steel, anything that fights the tap 21.5 mm 0.8465 21.50 64.2%
Form (roll) tap Theoretical 22.67 mm - starting point, check your tap maker's chart 22.5 mm 0.8858 22.50 —

Clearance holes for a M24 x 3 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 M24 x 3 per ISO 273. Clearance depends on the bolt diameter alone, so every M24 thread shares these figures.
Fit Hole mm Hole in
Fine 25.00 0.9843
Medium 26.00 1.0236
Coarse 28.00 1.1024

M24 x 3 dimensions

Nominal dimensions for M24 x 3. 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 0.9449 24.00
Basic internal minor diameter 0.817 20.75
Pitch 0.1181 3.00
Thread designation M24 x 3

What the hole looks like

Cross-section of a M24 x 3 tapped hole, drawn to scale The drilled hole is 21 mm, 0.8268 inches or 21.00 millimetres across. The tap cuts outward from that wall to the major diameter of 0.9449 inches. A 100 percent thread would reach in to the basic minor diameter of 0.817 inches, shown as a dashed line; the difference is why this drill gives 77.0% of thread. major 24 mm drill 21 mm · 21 mm dashed = 100% thread at 20.75 mm
M24 x 3 in section, to scale. The accent line is the thread the tap cuts from a 21 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 M24 x 3

Pre-filled with M24 x 3. 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

27/32″0.8438 in21.43 mm65.9% thread

Theoretical hole 21.27 mm

One size down, deeper thread53/64″ 0.8281 in · 76.1%

One size up, easier tapping21.5 mm 0.8465 in · 64.2%

For comparison, the published chart drill for M24 x 3 is 21 mm at 77.0% thread.

Notes on M24 x 3

Coarse pitch
M24 x 3 is the coarse pitch at 24 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: M24 x 2, M24 x 1.5.
What the standard drill gives you
21 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
21.5 mm opens the hole to 64.2% 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: 22.5 mm, against a theoretical 22.67 mm. Treat that as a starting point and check your tap maker's chart.
Closest inch size
1-8 is the nearest inch thread by diameter (25.4 mm against 24 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

1-8 7/8″ · 0.875 in · 22.23 mm · 77.0% 25.4 mm major against 24 mm

Not interchangeable. 1-8 is the nearest size by diameter, nothing more. The pitches differ, so a 1-8 fastener will not run into a M24 x 3 hole and forcing one will strip both.

Guides for tapping M24 x 3

Longer reads on the decisions behind the numbers above.

All guides →

M24 x 3 tap drill: common questions

What size drill bit do I need for a M24 x 3 tap?
A 21 mm drill, 0.8268 in. That leaves 77.0% of thread, which is the standard chart figure for M24 x 3.
What is the drill size for a M24 x 3 tap in inches?
The 21 mm tap drill measures 0.8268 in. If you only have inch drills, 53/64 in (0.8281 in) is the closest, giving 76.1% thread.
What drill should I use for M24 x 3 in stainless steel?
Use 21.5 mm instead of 21 mm. It leaves 64.2% of thread rather than 77.0%, so there is less material for the tap to cut and less chance of snapping it.
Is M24 x 3 the same as M24 x 2?
No. Both are 24 mm threads, but the pitch differs, so the drills differ: 21 mm for M24 x 3 and 22 mm for M24 x 2. The taps and the fasteners are not interchangeable.
What is the clearance hole for an M24 x 3 bolt?
For a medium fit, 26 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.