What is a 1.8 mm drill in decimal and mm?

0.0709 in, or 1.800 mm; nearest fractional drill: 5/64" (0.0781 in, +0.0073 in); nearest number / letter drill: #50 (0.0700 in, -0.0009 in).

What RPM for a 1.8 mm drill in steel?

In low-carbon steel (1018) an HSS 1.8 mm drill (0.0709 in) runs about 4,850 RPM at 90 SFM; a carbide drill about 16,170 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a 1.8 mm drill?

About 0.0017 in/rev in mild steel, 0.0016 in/rev in aluminum and 0.0011 in/rev in 304 stainless. At 4,850 RPM that is 8.24 IPM in steel (IPM = RPM × IPR).

What RPM for a 1.8 mm drill in aluminum?

13,470 RPM with HSS (250 SFM) or up to 32,340 RPM with carbide (600 SFM), feeding about 0.0016 in/rev.

What tap uses a 1.8 mm drill?

M2x0.4 (form (roll) tap, 65% thread).

1.8 mm drill size

A 1.8 mm metric drill is 0.0709 in (1.800 mm). It is the form (roll) tap, 65% thread drill for M2x0.4.

Decimal inch: 0.0709
Millimeters: 1.800
Nearest 1/64: 5/64" (-0.0073)
Type: metric drill

Nearest equivalents in other systems

Drills closest to 1.8 mm
System	Drill	Inch	mm	Difference
Fractional	5/64"	0.0781	1.984	+0.0073 in
Number / letter	#50	0.0700	1.778	-0.0009 in

Speeds and feeds: in mild steel an HSS drill starts at about 4,850 RPM and 0.0017 in/rev (8.24 IPM); in 6061 aluminum about 13,470 RPM.

1.8 mm drill speeds and feeds by material

Jobber-length twist drill, D = 0.0709 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

1.8 mm drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	13,470	600	32,340	0.0016	21.6	51.7
Brass / free-machining	150	8,080	400	21,560	0.0014	11.3	30.2
Low-carbon steel (1018)	90	4,850	300	16,170	0.0017	8.24	27.5
Alloy steel (4140, annealed)	70	3,770	250	13,470	0.0017	6.41	22.9
Stainless 304	40	2,160	150	8,080	0.0011	2.38	8.89
Gray cast iron	80	4,310	250	13,470	0.0010	4.31	13.5
Titanium 6Al-4V	25	1,350	100	5,390	0.0009	1.21	4.85
Plastics (acetal)	300	16,170	500	26,950	0.0028	45.3	75.5

Small drills: the computed RPM is above most spindles. Run at your spindle's maximum and keep the feed per rev; feed drops in proportion.

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 4,850 RPM × 0.043 mm/rev = 209 mm/min.

Worked example: 1.8 mm drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.0709 ≈ 4,850 RPM.
Feed for a 0.071 in drill in mild steel ≈ 0.0017 in/rev.
IPM = 4,850 × 0.0017 = 8.24 IPM.

Peck cycle by hole depth

1.8 mm drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 0.213 in (5.4 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 0.354 in (9 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 0.567 in (14.4 mm)	G83 full retract	0.5-1 × D, shrinking with depth	Retract to clear chips; reduce feed ~10-20% past 5×D.

Taps that use a 1.8 mm drill

M2x0.4 — form (roll) tap, 65% thread · tap speeds and feeds

Nearest drills

#50: 0.0700 in / 1.778 mm (-0.0009 in)
1.85 mm: 0.0728 in / 1.850 mm (+0.0020 in)
1.75 mm: 0.0689 in / 1.750 mm (-0.0020 in)
#49: 0.0730 in / 1.854 mm (+0.0021 in)

Drill speed calculator, prefilled for 1.8 mm Drill finder: sizes near 1.8 mm Metric drill chart Decimal equivalent chart

Common questions

What is a 1.8 mm drill in decimal and mm?: 0.0709 in, or 1.800 mm; nearest fractional drill: 5/64" (0.0781 in, +0.0073 in); nearest number / letter drill: #50 (0.0700 in, -0.0009 in).
What RPM for a 1.8 mm drill in steel?: In low-carbon steel (1018) an HSS 1.8 mm drill (0.0709 in) runs about 4,850 RPM at 90 SFM; a carbide drill about 16,170 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a 1.8 mm drill?: About 0.0017 in/rev in mild steel, 0.0016 in/rev in aluminum and 0.0011 in/rev in 304 stainless. At 4,850 RPM that is 8.24 IPM in steel (IPM = RPM × IPR).
What RPM for a 1.8 mm drill in aluminum?: 13,470 RPM with HSS (250 SFM) or up to 32,340 RPM with carbide (600 SFM), feeding about 0.0016 in/rev.
What tap uses a 1.8 mm drill?: M2x0.4 (form (roll) tap, 65% thread).

Nearby drill sizes

Sources

Machinery's Handbook, 31st ed., Speeds and Feeds for Drilling, Reaming and Threading (Tables 17-23) — HSS and carbide drilling SFM (rounded).
RedLine Tools (Productivity Inc.) catalog p. 340, Cobalt & HSS Drills Speeds & Feeds — feed per rev by drill diameter and material (middle of the catalog range).
ASME B94.11M twist drills: number (#1-#80) and letter (A-Z) drill sizes; drill size reference.

Material feed multipliers (aluminum 1.3×, brass 1.1×, 4140 0.85×, stainless and titanium 0.7× the mild-steel feed) are JobLine estimates. Peck guidance is JobLine shop practice. Use your drill maker's data first.

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