What is a #25 drill in decimal and mm?

0.1495 in, or 3.797 mm; nearest fractional drill: 5/32" (0.1563 in, +0.0067 in); nearest metric drill: 3.8 mm (0.1496 in, +0.0001 in).

What RPM for a #25 drill in steel?

In low-carbon steel (1018) an HSS #25 drill (0.1495 in) runs about 2,300 RPM at 90 SFM; a carbide drill about 7,660 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a #25 drill?

About 0.0036 in/rev in mild steel, 0.0035 in/rev in aluminum and 0.0024 in/rev in 304 stainless. At 2,300 RPM that is 8.28 IPM in steel (IPM = RPM × IPR).

What RPM for a #25 drill in aluminum?

6,390 RPM with HSS (250 SFM) or up to 15,330 RPM with carbide (600 SFM), feeding about 0.0035 in/rev.

What tap uses a #25 drill?

10-24 (cut tap, 75% thread); 8-32 (form (roll) tap, 65% thread); 6-32 (Helicoil / STI insert (#6-32×1D)).

#25 drill size

A #25 number (wire-gauge) drill is 0.1495 in (3.797 mm). It is the cut tap, 75% thread drill for 10-24.

Decimal inch: 0.1495
Millimeters: 3.797
Nearest 1/64: 5/32" (-0.0068)
Type: number (wire-gauge) drill

Nearest equivalents in other systems

Drills closest to #25
System	Drill	Inch	mm	Difference
Fractional	5/32"	0.1563	3.969	+0.0067 in
Metric	3.8 mm	0.1496	3.800	+0.0001 in

Speeds and feeds: in mild steel an HSS drill starts at about 2,300 RPM and 0.0036 in/rev (8.28 IPM); in 6061 aluminum about 6,390 RPM.

#25 drill speeds and feeds by material

Jobber-length twist drill, D = 0.1495 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

#25 drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	6,390	600	15,330	0.0035	22.4	53.7
Brass / free-machining	150	3,830	400	10,220	0.0030	11.5	30.7
Low-carbon steel (1018)	90	2,300	300	7,660	0.0036	8.28	27.6
Alloy steel (4140, annealed)	70	1,790	250	6,390	0.0036	6.44	23.0
Stainless 304	40	1,020	150	3,830	0.0024	2.45	9.19
Gray cast iron	80	2,040	250	6,390	0.0023	4.69	14.7
Titanium 6Al-4V	25	640	100	2,550	0.0018	1.15	4.59
Plastics (acetal)	300	7,660	500	12,770	0.0048	36.8	61.3

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 2,300 RPM × 0.091 mm/rev = 210 mm/min.

Worked example: #25 drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.1495 ≈ 2,300 RPM.
Feed for a 0.149 in drill in mild steel ≈ 0.0036 in/rev.
IPM = 2,300 × 0.0036 = 8.28 IPM.

Peck cycle by hole depth

#25 drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 0.449 in (11.4 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 0.747 in (19 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 1.196 in (30.4 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 #25 drill

10-24 — cut tap, 75% thread · tap speeds and feeds
8-32 — form (roll) tap, 65% thread · tap speeds and feeds
6-32 — Helicoil / STI insert (#6-32×1D) · tap speeds and feeds

Nearest drills

3.8 mm: 0.1496 in / 3.800 mm (+0.0001 in)
#26: 0.1470 in / 3.734 mm (-0.0025 in)
#24: 0.1520 in / 3.861 mm (+0.0025 in)
3.7 mm: 0.1457 in / 3.700 mm (-0.0038 in)

Drill speed calculator, prefilled for #25 Drill finder: sizes near #25 Number drill chart Decimal equivalent chart

Common questions

What is a #25 drill in decimal and mm?: 0.1495 in, or 3.797 mm; nearest fractional drill: 5/32" (0.1563 in, +0.0067 in); nearest metric drill: 3.8 mm (0.1496 in, +0.0001 in).
What RPM for a #25 drill in steel?: In low-carbon steel (1018) an HSS #25 drill (0.1495 in) runs about 2,300 RPM at 90 SFM; a carbide drill about 7,660 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a #25 drill?: About 0.0036 in/rev in mild steel, 0.0035 in/rev in aluminum and 0.0024 in/rev in 304 stainless. At 2,300 RPM that is 8.28 IPM in steel (IPM = RPM × IPR).
What RPM for a #25 drill in aluminum?: 6,390 RPM with HSS (250 SFM) or up to 15,330 RPM with carbide (600 SFM), feeding about 0.0035 in/rev.
What tap uses a #25 drill?: 10-24 (cut tap, 75% thread); 8-32 (form (roll) tap, 65% thread); 6-32 (Helicoil / STI insert (#6-32×1D)).

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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