What is a #4 drill in decimal and mm?

0.2090 in, or 5.309 mm; nearest fractional drill: 13/64" (0.2031 in, -0.0059 in); nearest metric drill: 5.3 mm (0.2087 in, -0.0003 in).

What RPM for a #4 drill in steel?

In low-carbon steel (1018) an HSS #4 drill (0.2090 in) runs about 1,640 RPM at 90 SFM; a carbide drill about 5,480 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a #4 drill?

About 0.0053 in/rev in mild steel, 0.0050 in/rev in aluminum and 0.0035 in/rev in 304 stainless. At 1,640 RPM that is 8.69 IPM in steel (IPM = RPM × IPR).

What RPM for a #4 drill in aluminum?

4,570 RPM with HSS (250 SFM) or up to 10,970 RPM with carbide (600 SFM), feeding about 0.0050 in/rev.

What size is a #4 drill?

0.2090 in / 5.309 mm. The nearest other drills are 5.3 mm (0.2087 in), #5 (0.2055 in), 5.4 mm (0.2126 in).

#4 drill size

A #4 number (wire-gauge) drill is 0.2090 in (5.309 mm).

Decimal inch: 0.2090
Millimeters: 5.309
Nearest 1/64: 13/64" (+0.0059)
Type: number (wire-gauge) drill

Nearest equivalents in other systems

Drills closest to #4
System	Drill	Inch	mm	Difference
Fractional	13/64"	0.2031	5.159	-0.0059 in
Metric	5.3 mm	0.2087	5.300	-0.0003 in

Speeds and feeds: in mild steel an HSS drill starts at about 1,640 RPM and 0.0053 in/rev (8.69 IPM); in 6061 aluminum about 4,570 RPM.

#4 drill speeds and feeds by material

Jobber-length twist drill, D = 0.2090 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

#4 drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	4,570	600	10,970	0.0050	22.9	54.9
Brass / free-machining	150	2,740	400	7,310	0.0043	11.8	31.4
Low-carbon steel (1018)	90	1,640	300	5,480	0.0053	8.69	29.0
Alloy steel (4140, annealed)	70	1,280	250	4,570	0.0053	6.78	24.2
Stainless 304	40	730	150	2,740	0.0035	2.56	9.59
Gray cast iron	80	1,460	250	4,570	0.0036	5.26	16.4
Titanium 6Al-4V	25	460	100	1,830	0.0025	1.15	4.58
Plastics (acetal)	300	5,480	500	9,140	0.0043	23.6	39.3

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 1,640 RPM × 0.135 mm/rev = 221 mm/min.

Worked example: #4 drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.2090 ≈ 1,640 RPM.
Feed for a 0.209 in drill in mild steel ≈ 0.0053 in/rev.
IPM = 1,640 × 0.0053 = 8.69 IPM.

Peck cycle by hole depth

#4 drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 0.627 in (15.9 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 1.045 in (26.5 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 1.672 in (42.5 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 drill

No standard UNC, UNF or metric tap in our tables calls for a #4 drill. Use it for clearance, pilot or reamer prep holes.

Nearest drills

5.3 mm: 0.2087 in / 5.300 mm (-0.0003 in)
#5: 0.2055 in / 5.220 mm (-0.0035 in)
5.4 mm: 0.2126 in / 5.400 mm (+0.0036 in)
#3: 0.2130 in / 5.410 mm (+0.0040 in)

Drill speed calculator, prefilled for #4 Drill finder: sizes near #4 Number drill chart Decimal equivalent chart

Common questions

What is a #4 drill in decimal and mm?: 0.2090 in, or 5.309 mm; nearest fractional drill: 13/64" (0.2031 in, -0.0059 in); nearest metric drill: 5.3 mm (0.2087 in, -0.0003 in).
What RPM for a #4 drill in steel?: In low-carbon steel (1018) an HSS #4 drill (0.2090 in) runs about 1,640 RPM at 90 SFM; a carbide drill about 5,480 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a #4 drill?: About 0.0053 in/rev in mild steel, 0.0050 in/rev in aluminum and 0.0035 in/rev in 304 stainless. At 1,640 RPM that is 8.69 IPM in steel (IPM = RPM × IPR).
What RPM for a #4 drill in aluminum?: 4,570 RPM with HSS (250 SFM) or up to 10,970 RPM with carbide (600 SFM), feeding about 0.0050 in/rev.
What size is a #4 drill?: 0.2090 in / 5.309 mm. The nearest other drills are 5.3 mm (0.2087 in), #5 (0.2055 in), 5.4 mm (0.2126 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.

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