17.5 mm Drill

Decimal inches 0.6890″

Millimeters 17.5 mm

System Metric

Nearest equivalents in other systems

System	Nearest drill	Size	Difference
Fractional inch	11/16″	0.6875″ / 17.462 mm	−0.038 mm (−0.0015″)
Number (wire gauge)	#1	0.2280″ / 5.791 mm	−11.709 mm (−0.4610″)
Letter	Z	0.4130″ / 10.49 mm	−7.01 mm (−0.2760″)

Positive difference = cuts a slightly larger hole than 17.5 mm. Sizes beyond the window are listed with arrows — they are not close substitutes.

Tap drill for

Thread	Major diameter	Pitch
M20 × 2.5	0.7874″ / 20 mm	2.5 mm

The standard chart recommendation (≈75% thread engagement). Application-specific factors — material, hole depth, tap type — can justify a different drill.

Clearance drill for

Thread	Fit
M16 × 2	normal
M16 × 1.5	normal

Neighboring metric sizes

Drill	Decimal in	mm	vs 17.5 mm
16.5 mm	0.6496	16.5	−1 mm
17 mm	0.6693	17	−0.5 mm
17.5 mm	0.6890	17.5	—
18 mm	0.7087	18	+0.5 mm
18.5 mm	0.7283	18.5	+1 mm

Data provenance. ASME B94.11M, Twist Drills (standard drill size series) (ASME). Machinery’s Handbook — tap drill charts (Industrial Press). Millimeter and inch values are converted with the exact definition 1 in = 25.4 mm; the canonical dimension for this metric size is 17.5 mm. See all data sources.