What is a 9/32" drill in decimal and mm?

0.2813 in, or 7.144 mm; nearest number / letter drill: Letter K (0.2810 in, -0.0003 in); nearest metric drill: 7.1 mm (0.2795 in, -0.0017 in).

What RPM for a 9/32" drill in steel?

In low-carbon steel (1018) an HSS 9/32" drill (0.2813 in) runs about 1,220 RPM at 90 SFM; a carbide drill about 4,070 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a 9/32" drill?

About 0.0073 in/rev in mild steel, 0.0066 in/rev in aluminum and 0.0048 in/rev in 304 stainless. At 1,220 RPM that is 8.91 IPM in steel (IPM = RPM × IPR).

What RPM for a 9/32" drill in aluminum?

3,400 RPM with HSS (250 SFM) or up to 8,150 RPM with carbide (600 SFM), feeding about 0.0066 in/rev.

What tap uses a 9/32" drill?

5/16-32 (cut tap, 75% thread); 5/16-24 (cut tap, 50% thread).

9/32" drill size

A 9/32" fractional drill is 0.2813 in (7.144 mm). It is the cut tap, 75% thread drill for 5/16-32.

Decimal inch: 0.2813
Millimeters: 7.144
Nearest 1/64: 9/32" (+0.0000)
Type: fractional drill

Nearest equivalents in other systems

Drills closest to 9/32"
System	Drill	Inch	mm	Difference
Number / letter	Letter K	0.2810	7.137	-0.0003 in
Metric	7.1 mm	0.2795	7.100	-0.0017 in

Speeds and feeds: in mild steel an HSS drill starts at about 1,220 RPM and 0.0073 in/rev (8.91 IPM); in 6061 aluminum about 3,400 RPM.

9/32" drill speeds and feeds by material

Jobber-length twist drill, D = 0.2813 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

9/32" drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	3,400	600	8,150	0.0066	22.4	53.8
Brass / free-machining	150	2,040	400	5,430	0.0055	11.2	29.9
Low-carbon steel (1018)	90	1,220	300	4,070	0.0073	8.91	29.7
Alloy steel (4140, annealed)	70	950	250	3,400	0.0075	7.13	25.5
Stainless 304	40	540	150	2,040	0.0048	2.59	9.79
Gray cast iron	80	1,090	250	3,400	0.0050	5.45	17.0
Titanium 6Al-4V	25	340	100	1,360	0.0033	1.12	4.49
Plastics (acetal)	300	4,070	500	6,790	0.0043	17.5	29.2

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 1,220 RPM × 0.185 mm/rev = 226 mm/min.

Worked example: 9/32" drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.2813 ≈ 1,220 RPM.
Feed for a 0.281 in drill in mild steel ≈ 0.0073 in/rev.
IPM = 1,220 × 0.0073 = 8.91 IPM.

Peck cycle by hole depth

9/32" drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 0.844 in (21.4 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 1.406 in (35.7 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 2.250 in (57.2 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 9/32" drill

5/16-32 — cut tap, 75% thread
5/16-24 — cut tap, 50% thread · tap speeds and feeds

Nearest drills

Letter K: 0.2810 in / 7.137 mm (-0.0003 in)
7.1 mm: 0.2795 in / 7.100 mm (-0.0017 in)
7.2 mm: 0.2835 in / 7.200 mm (+0.0022 in)
Letter J: 0.2770 in / 7.036 mm (-0.0043 in)

Drill speed calculator, prefilled for 9/32"Drill finder: sizes near 9/32"Fractional drill chart Decimal equivalent chart

Common questions

What is a 9/32" drill in decimal and mm?: 0.2813 in, or 7.144 mm; nearest number / letter drill: Letter K (0.2810 in, -0.0003 in); nearest metric drill: 7.1 mm (0.2795 in, -0.0017 in).
What RPM for a 9/32" drill in steel?: In low-carbon steel (1018) an HSS 9/32" drill (0.2813 in) runs about 1,220 RPM at 90 SFM; a carbide drill about 4,070 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a 9/32" drill?: About 0.0073 in/rev in mild steel, 0.0066 in/rev in aluminum and 0.0048 in/rev in 304 stainless. At 1,220 RPM that is 8.91 IPM in steel (IPM = RPM × IPR).
What RPM for a 9/32" drill in aluminum?: 3,400 RPM with HSS (250 SFM) or up to 8,150 RPM with carbide (600 SFM), feeding about 0.0066 in/rev.
What tap uses a 9/32" drill?: 5/16-32 (cut tap, 75% thread); 5/16-24 (cut tap, 50% 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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