BenchReference

M12 × 1.25 Thread

Recommended tap drill 10.8 mm
Tap drill Ø 0.4252″ / 10.8 mm
Major Ø 0.4724″ / 12 mm
Pitch 1.25 mm

The chart recommendation gives approximately 73.9% thread engagement — the conventional target for average materials. It is not the only valid choice; see the options below.

Specification

DesignationM12 × 1.25
Thread familyISO metric fine
Nominal sizeM12
Basic major diameter 0.4724″ / 12 mm
Pitch1.25 mm
Recommended tap drill 10.8 mm (0.4252″ / 10.8 mm)
P = 1.25 mm 60° major Ø 12 mm 60° thread form (UN / ISO) — schematic

Tap drill options by thread engagement

Any of these standard drills produces a usable engagement for M12 × 1.25; smaller drills give stronger threads but higher tapping torque. Percentages use the conventional approximation (60° thread form).

10.7 mm 80.1% 10.8 mm ★ 73.9% 11 mm 61.6% shaded = share of the full thread height the tap forms · accent line = drilled hole wall
★ = chart recommendation. A smaller drill leaves more of the thread height for the tap to form.
Drill Decimal in mm Approx. engagement
10.7 mm 0.4213 10.7 80.1%
27/64″ 0.4219 10.716 79.1%
10.8 mm — chart recommendation 0.4252 10.8 73.9%
10.9 mm 0.4291 10.9 67.7%
11 mm 0.4331 11 61.6%

Nearest drills to the tap drill in other systems

Drill Size vs 10.8 mm Resulting engagement
27/64″ 0.4219″ / 10.716 mm −0.084 mm 79.1%
Z 0.4130″ / 10.49 mm −0.31 mm 93%

Clearance holes

For a bolt or screw of this size to pass through freely. ISO 273 series (fine/medium/coarse), shown as close, normal, and loose.

Tapped hole Clearance hole 10.8 mm tap drill threads cut into the material 13.5 mm (normal fit) the tinted gap lets the bolt pass freely
Schematic — proportions exaggerated for clarity; use the table values.
Fit Drill / Ø Decimal in mm
close 13 mm 0.5118 13
normal 13.5 mm 0.5315 13.5
loose 14.5 mm 0.5709 14.5

Hex bolt & nut dimensions

For a standard hex bolt (ISO 4014/4017) and style-1 nut (ISO 4032) in this size.

Wrench / socket size (bolt head) 18 mm — legacy DIN: 19 mm
Head height 7.5 mm
Nut thickness 10.8 mm
Compatible nut M12 × 1.25 hex nut
Head — top view Bolt — side view Nut — side view width across flats = 18 mm wrench head height 7.5 mm thickness 10.8 mm

Basic (nominal) dimensions. See the wrench & socket size charts for all sizes and the metric ↔ SAE socket comparison.

Related threads

Data provenance. ISO 261 / ISO 724, ISO general purpose metric screw threads (ISO). ISO 2306, Drills for use prior to tapping screw threads (ISO). ISO 273, Clearance holes for bolts and screws (ISO). ISO 4014 / ISO 4017, Hexagon head bolts and screws (ISO). ISO 4032, Hexagon regular nuts, style 1 (ISO). Engagement percentages use the conventional approximation (engagement = (major − drill) ÷ (1.29904 × pitch)) and are guidance, not a tolerance specification. See all data sources.