What is a #3 drill in decimal and mm?

0.2130 in, or 5.410 mm; nearest fractional drill: 7/32" (0.2188 in, +0.0057 in); nearest metric drill: 5.4 mm (0.2126 in, -0.0004 in).

What RPM for a #3 drill in steel?

In low-carbon steel (1018) an HSS #3 drill (0.2130 in) runs about 1,610 RPM at 90 SFM; a carbide drill about 5,380 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a #3 drill?

About 0.0054 in/rev in mild steel, 0.0051 in/rev in aluminum and 0.0036 in/rev in 304 stainless. At 1,610 RPM that is 8.69 IPM in steel (IPM = RPM × IPR).

What RPM for a #3 drill in aluminum?

4,480 RPM with HSS (250 SFM) or up to 10,760 RPM with carbide (600 SFM), feeding about 0.0051 in/rev.

What tap uses a #3 drill?

1/4-28 (cut tap, 75% thread); 10-32 (Helicoil / STI insert (#10-32×1D)).

#3 drill size

A #3 number (wire-gauge) drill is 0.2130 in (5.410 mm). It is the cut tap, 75% thread drill for 1/4-28.

Decimal inch: 0.2130
Millimeters: 5.410
Nearest 1/64: 7/32" (-0.0058)
Type: number (wire-gauge) drill

Nearest equivalents in other systems

Drills closest to #3
System	Drill	Inch	mm	Difference
Fractional	7/32"	0.2188	5.556	+0.0057 in
Metric	5.4 mm	0.2126	5.400	-0.0004 in

Speeds and feeds: in mild steel an HSS drill starts at about 1,610 RPM and 0.0054 in/rev (8.69 IPM); in 6061 aluminum about 4,480 RPM.

#3 drill speeds and feeds by material

Jobber-length twist drill, D = 0.2130 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

#3 drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	4,480	600	10,760	0.0051	22.9	54.9
Brass / free-machining	150	2,690	400	7,170	0.0044	11.8	31.6
Low-carbon steel (1018)	90	1,610	300	5,380	0.0054	8.69	29.1
Alloy steel (4140, annealed)	70	1,260	250	4,480	0.0054	6.80	24.2
Stainless 304	40	720	150	2,690	0.0036	2.59	9.68
Gray cast iron	80	1,430	250	4,480	0.0037	5.29	16.6
Titanium 6Al-4V	25	450	100	1,790	0.0026	1.17	4.65
Plastics (acetal)	300	5,380	500	8,970	0.0043	23.1	38.6

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 1,610 RPM × 0.137 mm/rev = 221 mm/min.

Worked example: #3 drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.2130 ≈ 1,610 RPM.
Feed for a 0.213 in drill in mild steel ≈ 0.0054 in/rev.
IPM = 1,610 × 0.0054 = 8.69 IPM.

Peck cycle by hole depth

#3 drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 0.639 in (16.2 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 1.065 in (27.1 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 1.704 in (43.3 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 #3 drill

1/4-28 — cut tap, 75% thread · tap speeds and feeds
10-32 — Helicoil / STI insert (#10-32×1D) · tap speeds and feeds

Nearest drills

5.4 mm: 0.2126 in / 5.400 mm (-0.0004 in)
5.5 mm: 0.2165 in / 5.500 mm (+0.0035 in)
#4: 0.2090 in / 5.309 mm (-0.0040 in)
5.3 mm: 0.2087 in / 5.300 mm (-0.0043 in)

Drill speed calculator, prefilled for #3 Drill finder: sizes near #3 Number drill chart Decimal equivalent chart

Common questions

What is a #3 drill in decimal and mm?: 0.2130 in, or 5.410 mm; nearest fractional drill: 7/32" (0.2188 in, +0.0057 in); nearest metric drill: 5.4 mm (0.2126 in, -0.0004 in).
What RPM for a #3 drill in steel?: In low-carbon steel (1018) an HSS #3 drill (0.2130 in) runs about 1,610 RPM at 90 SFM; a carbide drill about 5,380 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a #3 drill?: About 0.0054 in/rev in mild steel, 0.0051 in/rev in aluminum and 0.0036 in/rev in 304 stainless. At 1,610 RPM that is 8.69 IPM in steel (IPM = RPM × IPR).
What RPM for a #3 drill in aluminum?: 4,480 RPM with HSS (250 SFM) or up to 10,760 RPM with carbide (600 SFM), feeding about 0.0051 in/rev.
What tap uses a #3 drill?: 1/4-28 (cut tap, 75% thread); 10-32 (Helicoil / STI insert (#10-32×1D)).

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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