BenchReference

3/4″-16 UNF Thread

Recommended tap drill 11/16″
Tap drill Ø 0.6875″ / 17.462 mm
Major Ø 0.7500″ / 19.05 mm
Threads per inch 16

The chart recommendation gives approximately 77% thread engagement — the conventional target for average materials. It is not the only valid choice; see the options below.

Specification

Designation3/4″-16 UNF
Thread familyUnified National Fine (UNF)
Nominal size3/4
Basic major diameter 0.7500″ / 19.05 mm
Threads per inch / pitch16 TPI (1.587 mm pitch)
Recommended tap drill 11/16″ (0.6875″ / 17.462 mm)
P = 0.0625″ (16 TPI) 60° major Ø 0.7500″ 60° thread form (UN / ISO) — schematic

Tap drill options by thread engagement

Any of these standard drills produces a usable engagement for 3/4″-16 UNF; smaller drills give stronger threads but higher tapping torque. Percentages use the conventional approximation (60° thread form).

11/16″ ★ 77% 17.5 mm 75.2% 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
11/16″ — chart recommendation 0.6875 17.462 77%
17.5 mm 0.6890 17.5 75.2%

Nearest drills to the tap drill in other systems

Drill Size vs 11/16″ Resulting engagement
17.5 mm 0.6890″ / 17.5 mm +0.038 mm 75.2%

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 11/16" tap drill threads cut into the material 13/16" (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 25/32″ 0.7813 19.844
normal 13/16″ 0.8125 20.637
loose 29/32″ 0.9063 23.019

Hex bolt & nut dimensions

For a standard hex cap screw (ASME B18.2.1) and finished hex nut (ASME B18.2.2) in this size.

Wrench / socket size (bolt head) 1-1/8″
Head height 15/32″ (0.4688″)
Nut thickness 41/64″ (0.6406″)
Compatible nut 3/4-16 hex nut
Head — top view Bolt — side view Nut — side view width across flats = 1-1/8″ wrench head height 15/32″ thickness 41/64″

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

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). ASME B18.2.1, Hex Cap Screws (head dimensions) (ASME). ASME B18.2.2, Finished Hex Nuts (ASME). Engagement percentages use the conventional approximation (engagement = (major − drill) ÷ (1.29904 × pitch)) and are guidance, not a tolerance specification. See all data sources.