What is a 4.0 mm drill in decimal and mm?

0.1575 in, or 4.000 mm; nearest fractional drill: 5/32" (0.1563 in, -0.0012 in); nearest number / letter drill: #22 (0.1570 in, -0.0005 in).

What RPM for a 4.0 mm drill in steel?

In low-carbon steel (1018) an HSS 4.0 mm drill (0.1575 in) runs about 2,180 RPM at 90 SFM; a carbide drill about 7,280 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a 4.0 mm drill?

About 0.0039 in/rev in mild steel, 0.0037 in/rev in aluminum and 0.0026 in/rev in 304 stainless. At 2,180 RPM that is 8.50 IPM in steel (IPM = RPM × IPR).

What RPM for a 4.0 mm drill in aluminum?

6,060 RPM with HSS (250 SFM) or up to 14,550 RPM with carbide (600 SFM), feeding about 0.0037 in/rev.

What size is a 4.0 mm drill?

0.1575 in / 4.000 mm. The nearest other drills are #22 (0.1570 in), 5/32" (0.1563 in), #21 (0.1590 in).

4.0 mm drill size

A 4.0 mm metric drill is 0.1575 in (4.000 mm).

Decimal inch: 0.1575
Millimeters: 4.000
Nearest 1/64: 5/32" (+0.0012)
Type: metric drill

Nearest equivalents in other systems

Drills closest to 4.0 mm
System	Drill	Inch	mm	Difference
Fractional	5/32"	0.1563	3.969	-0.0012 in
Number / letter	#22	0.1570	3.988	-0.0005 in

Speeds and feeds: in mild steel an HSS drill starts at about 2,180 RPM and 0.0039 in/rev (8.50 IPM); in 6061 aluminum about 6,060 RPM.

4.0 mm drill speeds and feeds by material

Jobber-length twist drill, D = 0.1575 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

4.0 mm drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	6,060	600	14,550	0.0037	22.4	53.8
Brass / free-machining	150	3,640	400	9,700	0.0031	11.3	30.1
Low-carbon steel (1018)	90	2,180	300	7,280	0.0039	8.50	28.4
Alloy steel (4140, annealed)	70	1,700	250	6,060	0.0039	6.63	23.6
Stainless 304	40	970	150	3,640	0.0026	2.52	9.46
Gray cast iron	80	1,940	250	6,060	0.0025	4.85	15.2
Titanium 6Al-4V	25	610	100	2,430	0.0019	1.16	4.62
Plastics (acetal)	300	7,280	500	12,130	0.0047	34.2	57.0

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 2,180 RPM × 0.099 mm/rev = 216 mm/min.

Worked example: 4.0 mm drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.1575 ≈ 2,180 RPM.
Feed for a 0.157 in drill in mild steel ≈ 0.0039 in/rev.
IPM = 2,180 × 0.0039 = 8.50 IPM.

Peck cycle by hole depth

4.0 mm drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 0.472 in (12 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 0.787 in (20 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 1.260 in (32 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 4.0 mm drill

No standard UNC, UNF or metric tap in our tables calls for a 4.0 mm drill. Use it for clearance, pilot or reamer prep holes.

Nearest drills

#22: 0.1570 in / 3.988 mm (-0.0005 in)
5/32": 0.1563 in / 3.969 mm (-0.0012 in)
#21: 0.1590 in / 4.039 mm (+0.0015 in)
#23: 0.1540 in / 3.912 mm (-0.0035 in)

Drill speed calculator, prefilled for 4.0 mm Drill finder: sizes near 4.0 mm Metric drill chart Decimal equivalent chart

Common questions

What is a 4.0 mm drill in decimal and mm?: 0.1575 in, or 4.000 mm; nearest fractional drill: 5/32" (0.1563 in, -0.0012 in); nearest number / letter drill: #22 (0.1570 in, -0.0005 in).
What RPM for a 4.0 mm drill in steel?: In low-carbon steel (1018) an HSS 4.0 mm drill (0.1575 in) runs about 2,180 RPM at 90 SFM; a carbide drill about 7,280 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a 4.0 mm drill?: About 0.0039 in/rev in mild steel, 0.0037 in/rev in aluminum and 0.0026 in/rev in 304 stainless. At 2,180 RPM that is 8.50 IPM in steel (IPM = RPM × IPR).
What RPM for a 4.0 mm drill in aluminum?: 6,060 RPM with HSS (250 SFM) or up to 14,550 RPM with carbide (600 SFM), feeding about 0.0037 in/rev.
What size is a 4.0 mm drill?: 0.1575 in / 4.000 mm. The nearest other drills are #22 (0.1570 in), 5/32" (0.1563 in), #21 (0.1590 in).

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.

Free for machinists & programmers

Put your skills on a free talent profile

Machines, controls, certs and saved calculations in one profile shops can find.

Create free profile

For your shop

Bring shift handoffs to your shop

Stop losing job status between shifts. Every station's notes, counts and issues, handed off cleanly.

See shift handoffs