What is a #24 drill in decimal and mm?

0.1520 in, or 3.861 mm; nearest fractional drill: 5/32" (0.1563 in, +0.0043 in); nearest metric drill: 3.9 mm (0.1535 in, +0.0015 in).

What RPM for a #24 drill in steel?

In low-carbon steel (1018) an HSS #24 drill (0.1520 in) runs about 2,260 RPM at 90 SFM; a carbide drill about 7,540 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a #24 drill?

About 0.0037 in/rev in mild steel, 0.0035 in/rev in aluminum and 0.0025 in/rev in 304 stainless. At 2,260 RPM that is 8.36 IPM in steel (IPM = RPM × IPR).

What RPM for a #24 drill in aluminum?

6,280 RPM with HSS (250 SFM) or up to 15,080 RPM with carbide (600 SFM), feeding about 0.0035 in/rev.

What tap uses a #24 drill?

8-36 (form (roll) tap, 65% thread).

#24 drill size

A #24 number (wire-gauge) drill is 0.1520 in (3.861 mm). It is the form (roll) tap, 65% thread drill for 8-36.

Decimal inch: 0.1520
Millimeters: 3.861
Nearest 1/64: 5/32" (-0.0043)
Type: number (wire-gauge) drill

Nearest equivalents in other systems

Drills closest to #24
System	Drill	Inch	mm	Difference
Fractional	5/32"	0.1563	3.969	+0.0043 in
Metric	3.9 mm	0.1535	3.900	+0.0015 in

Speeds and feeds: in mild steel an HSS drill starts at about 2,260 RPM and 0.0037 in/rev (8.36 IPM); in 6061 aluminum about 6,280 RPM.

#24 drill speeds and feeds by material

Jobber-length twist drill, D = 0.1520 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

#24 drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	6,280	600	15,080	0.0035	22.0	52.8
Brass / free-machining	150	3,770	400	10,050	0.0030	11.3	30.1
Low-carbon steel (1018)	90	2,260	300	7,540	0.0037	8.36	27.9
Alloy steel (4140, annealed)	70	1,760	250	6,280	0.0037	6.51	23.2
Stainless 304	40	1,010	150	3,770	0.0025	2.53	9.43
Gray cast iron	80	2,010	250	6,280	0.0024	4.82	15.1
Titanium 6Al-4V	25	630	100	2,510	0.0019	1.20	4.77
Plastics (acetal)	300	7,540	500	12,560	0.0048	36.2	60.3

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 2,260 RPM × 0.094 mm/rev = 212 mm/min.

Worked example: #24 drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.1520 ≈ 2,260 RPM.
Feed for a 0.152 in drill in mild steel ≈ 0.0037 in/rev.
IPM = 2,260 × 0.0037 = 8.36 IPM.

Peck cycle by hole depth

#24 drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 0.456 in (11.6 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 0.760 in (19.3 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 1.216 in (30.9 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 #24 drill

8-36 — form (roll) tap, 65% thread · tap speeds and feeds

Nearest drills

3.9 mm: 0.1535 in / 3.900 mm (+0.0015 in)
#23: 0.1540 in / 3.912 mm (+0.0020 in)
3.8 mm: 0.1496 in / 3.800 mm (-0.0024 in)
#25: 0.1495 in / 3.797 mm (-0.0025 in)

Drill speed calculator, prefilled for #24 Drill finder: sizes near #24 Number drill chart Decimal equivalent chart

Common questions

What is a #24 drill in decimal and mm?: 0.1520 in, or 3.861 mm; nearest fractional drill: 5/32" (0.1563 in, +0.0043 in); nearest metric drill: 3.9 mm (0.1535 in, +0.0015 in).
What RPM for a #24 drill in steel?: In low-carbon steel (1018) an HSS #24 drill (0.1520 in) runs about 2,260 RPM at 90 SFM; a carbide drill about 7,540 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a #24 drill?: About 0.0037 in/rev in mild steel, 0.0035 in/rev in aluminum and 0.0025 in/rev in 304 stainless. At 2,260 RPM that is 8.36 IPM in steel (IPM = RPM × IPR).
What RPM for a #24 drill in aluminum?: 6,280 RPM with HSS (250 SFM) or up to 15,080 RPM with carbide (600 SFM), feeding about 0.0035 in/rev.
What tap uses a #24 drill?: 8-36 (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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