What is a 23/64" drill in decimal and mm?

0.3594 in, or 9.128 mm; nearest number / letter drill: Letter T (0.3580 in, -0.0014 in); nearest metric drill: 9.1 mm (0.3583 in, -0.0011 in).

What RPM for a 23/64" drill in steel?

In low-carbon steel (1018) an HSS 23/64" drill (0.3594 in) runs about 960 RPM at 90 SFM; a carbide drill about 3,190 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a 23/64" drill?

About 0.0091 in/rev in mild steel, 0.0082 in/rev in aluminum and 0.0060 in/rev in 304 stainless. At 960 RPM that is 8.74 IPM in steel (IPM = RPM × IPR).

What RPM for a 23/64" drill in aluminum?

2,660 RPM with HSS (250 SFM) or up to 6,380 RPM with carbide (600 SFM), feeding about 0.0082 in/rev.

What tap uses a 23/64" drill?

3/8-32 (form (roll) tap, 65% thread).

23/64" drill size

A 23/64" fractional drill is 0.3594 in (9.128 mm). It is the form (roll) tap, 65% thread drill for 3/8-32.

Decimal inch: 0.3594
Millimeters: 9.128
Nearest 1/64: 23/64" (+0.0000)
Type: fractional drill

Nearest equivalents in other systems

Drills closest to 23/64"
System	Drill	Inch	mm	Difference
Number / letter	Letter T	0.3580	9.093	-0.0014 in
Metric	9.1 mm	0.3583	9.100	-0.0011 in

Speeds and feeds: in mild steel an HSS drill starts at about 960 RPM and 0.0091 in/rev (8.74 IPM); in 6061 aluminum about 2,660 RPM.

23/64" drill speeds and feeds by material

Jobber-length twist drill, D = 0.3594 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

23/64" drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	2,660	600	6,380	0.0082	21.8	52.3
Brass / free-machining	150	1,590	400	4,250	0.0061	9.70	25.9
Low-carbon steel (1018)	90	960	300	3,190	0.0091	8.74	29.0
Alloy steel (4140, annealed)	70	740	250	2,660	0.0100	7.40	26.6
Stainless 304	40	430	150	1,590	0.0060	2.58	9.54
Gray cast iron	80	850	250	2,660	0.0062	5.27	16.5
Titanium 6Al-4V	25	270	100	1,060	0.0041	1.11	4.35
Plastics (acetal)	300	3,190	500	5,310	0.0049	15.6	26.0

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 960 RPM × 0.231 mm/rev = 222 mm/min.

Worked example: 23/64" drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.3594 ≈ 960 RPM.
Feed for a 0.359 in drill in mild steel ≈ 0.0091 in/rev.
IPM = 960 × 0.0091 = 8.74 IPM.

Peck cycle by hole depth

23/64" drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 1.078 in (27.4 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 1.797 in (45.6 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 2.875 in (73 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 23/64" drill

3/8-32 — form (roll) tap, 65% thread

Nearest drills

9.1 mm: 0.3583 in / 9.100 mm (-0.0011 in)
Letter T: 0.3580 in / 9.093 mm (-0.0014 in)
9.2 mm: 0.3622 in / 9.200 mm (+0.0028 in)
9.0 mm: 0.3543 in / 9.000 mm (-0.0050 in)

Drill speed calculator, prefilled for 23/64"Drill finder: sizes near 23/64"Fractional drill chart Decimal equivalent chart

Common questions

What is a 23/64" drill in decimal and mm?: 0.3594 in, or 9.128 mm; nearest number / letter drill: Letter T (0.3580 in, -0.0014 in); nearest metric drill: 9.1 mm (0.3583 in, -0.0011 in).
What RPM for a 23/64" drill in steel?: In low-carbon steel (1018) an HSS 23/64" drill (0.3594 in) runs about 960 RPM at 90 SFM; a carbide drill about 3,190 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a 23/64" drill?: About 0.0091 in/rev in mild steel, 0.0082 in/rev in aluminum and 0.0060 in/rev in 304 stainless. At 960 RPM that is 8.74 IPM in steel (IPM = RPM × IPR).
What RPM for a 23/64" drill in aluminum?: 2,660 RPM with HSS (250 SFM) or up to 6,380 RPM with carbide (600 SFM), feeding about 0.0082 in/rev.
What tap uses a 23/64" drill?: 3/8-32 (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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