Tap Drill Size Chart

M14 x 1.25 Tap Drill Size

Tap drill

12.8 mm 0.5039 in

Use a 12.8 mm drill (0.5039 in) for 73.9% thread.

The drill size for a M14 x 1.25 tap is 12.8 mm (0.5039 in). If you are wondering what size drill bit a M14 x 1.25 tap needs, that is the one: it leaves 73.9% 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 M14 x 1.25

Tap drills and clearance drills for M14 x 1.25 (Metric fine, 1.25 mm pitch). Percent of thread is the figure stored for each drill, which reproduces from the major diameter and pitch of M14 x 1.25.
Use Drill Decimal in mm % thread
Standard tap drill Cut tap, general use (D - P) 12.8 mm 0.5039 12.80 73.9%
Inch substitute Closest inch drill if you have no metric set 1/2″ 0.500 12.70 80.1%
Hard material Stainless, tool steel, anything that fights the tap 13 mm 0.5118 13.00 61.6%
Form (roll) tap Theoretical 13.45 mm - starting point, check your tap maker's chart 13.4 mm 0.5276 13.40 —

Clearance holes for a M14 x 1.25 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 M14 x 1.25 per ISO 273. Clearance depends on the bolt diameter alone, so every M14 thread shares these figures.
Fit Hole mm Hole in
Fine 15.00 0.5906
Medium 15.50 0.6102
Coarse 16.50 0.6496

M14 x 1.25 dimensions

Nominal dimensions for M14 x 1.25. 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 0.5512 14.00
Basic internal minor diameter 0.4979 12.65
Pitch 0.0492 1.25
Thread designation M14 x 1.25

What the hole looks like

Cross-section of a M14 x 1.25 tapped hole, drawn to scale The drilled hole is 12.8 mm, 0.5039 inches or 12.80 millimetres across. The tap cuts outward from that wall to the major diameter of 0.5512 inches. A 100 percent thread would reach in to the basic minor diameter of 0.4979 inches, shown as a dashed line; the difference is why this drill gives 73.9% of thread. major 14 mm drill 12.8 mm · 12.8 mm dashed = 100% thread at 12.65 mm
M14 x 1.25 in section, to scale. The accent line is the thread the tap cuts from a 12.8 mm hole; the dashed line is where the crest would sit at 100% thread. The gap between them is the 26.1% of thread this drill leaves behind.

Work out a different hole for M14 x 1.25

Pre-filled with M14 x 1.25. 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

12.9 mm0.5079 in67.7% thread

Theoretical hole 12.86 mm

One size down, deeper thread12.8 mm 0.5039 in · 73.9%

One size up, easier tapping13 mm 0.5118 in · 61.6%

For comparison, the published chart drill for M14 x 1.25 is 12.8 mm at 73.9% thread.

Notes on M14 x 1.25

Finest pitch at this diameter
M14 x 1.25 is the finest of the standard pitches at 14 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 M14 x 2.
Not the same as M14 x 2
M14 x 2 and M14 x 1.25 share a 14 mm major diameter but not a pitch, and they take different drills: 12 mm for M14 x 2, 12.8 mm for M14 x 1.25. The taps and the fasteners are not interchangeable.
What the standard drill gives you
12.8 mm leaves 73.9% of thread (D - P). That is in the normal 65-80% band most shop charts aim for.
Stainless, tool steel and other tough material
13 mm opens the hole to 61.6% 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: 13.4 mm, against a theoretical 13.45 mm. Treat that as a starting point and check your tap maker's chart.
Closest inch size
9/16-12 is the nearest inch thread by diameter (14.29 mm against 14 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

9/16-12 31/64″ · 0.4844 in · 12.30 mm · 72.1% 14.29 mm major against 14 mm

Not interchangeable. 9/16-12 is the nearest size by diameter, nothing more. The pitches differ, so a 9/16-12 fastener will not run into a M14 x 1.25 hole and forcing one will strip both.

Guides for tapping M14 x 1.25

Longer reads on the decisions behind the numbers above.

All guides →

M14 x 1.25 tap drill: common questions

What size drill bit do I need for a M14 x 1.25 tap?
A 12.8 mm drill, 0.5039 in. That leaves 73.9% of thread, which is the standard chart figure for M14 x 1.25.
What is the drill size for a M14 x 1.25 tap in inches?
The 12.8 mm tap drill measures 0.5039 in. If you only have inch drills, 1/2 in (0.500 in) is the closest, giving 80.1% thread.
What drill should I use for M14 x 1.25 in stainless steel?
Use 13 mm instead of 12.8 mm. It leaves 61.6% of thread rather than 73.9%, so there is less material for the tap to cut and less chance of snapping it.
Is M14 x 1.25 the same as M14 x 2?
No. Both are 14 mm threads, but the pitch differs, so the drills differ: 12.8 mm for M14 x 1.25 and 12 mm for M14 x 2. The taps and the fasteners are not interchangeable.
What is the clearance hole for an M14 x 1.25 bolt?
For a medium fit, 15.5 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.