BenchReference

#0-80 UNF Thread

Recommended tap drill 3/64″
Tap drill Ø 0.0469″ / 1.191 mm
Major Ø 0.0600″ / 1.524 mm
Threads per inch 80

The chart recommendation gives approximately 80.8% thread engagement — the conventional target for average materials. It is not the only valid choice; see the options below.

Specification

Designation#0-80 UNF
Thread familyUnified National Fine (UNF)
Nominal size#0
Basic major diameter 0.0600″ / 1.524 mm
Threads per inch / pitch80 TPI (0.318 mm pitch)
Recommended tap drill 3/64″ (0.0469″ / 1.191 mm)
P = 0.0125″ (80 TPI) 60° major Ø 0.0600″ 60° thread form (UN / ISO) — schematic

Tap drill options by thread engagement

Any of these standard drills produces a usable engagement for #0-80 UNF; smaller drills give stronger threads but higher tapping torque. Percentages use the conventional approximation (60° thread form).

#56 83.1% 3/64″ ★ 80.8% 1.25 mm 66.4% 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
#56 0.0465 1.181 83.1%
3/64″ — chart recommendation 0.0469 1.191 80.8%
1.2 mm 0.0472 1.2 78.6%
1.25 mm 0.0492 1.25 66.4%

Nearest drills to the tap drill in other systems

Drill Size vs 3/64″ Resulting engagement
1.2 mm 0.0472″ / 1.2 mm +0.009 mm 78.6%
#56 0.0465″ / 1.181 mm −0.01 mm 83.1%

Clearance holes

For a bolt or screw of this size to pass through freely. Recommended drills per ASME B18.2.8: close, normal, and loose fits.

Tapped hole Clearance hole 3/64" tap drill threads cut into the material #48 (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 #51 0.0670 1.702
normal #48 0.0760 1.93
loose 3/32″ 0.0938 2.381

Related threads

Data provenance. ASME B1.1, Unified Inch Screw Threads (ASME). Machinery’s Handbook — tap drill charts (Industrial Press). ASME B18.2.8, Clearance Holes for Bolts, Screws, and Studs (ASME). Engagement percentages use the conventional approximation (engagement = (major − drill) ÷ (1.29904 × pitch)) and are guidance, not a tolerance specification. See all data sources.