What is a 15/64" drill in decimal and mm?

0.2344 in, or 5.953 mm; nearest number / letter drill: Letter A (0.2340 in, -0.0004 in); nearest metric drill: 6.0 mm (0.2362 in, +0.0019 in).

What RPM for a 15/64" drill in steel?

In low-carbon steel (1018) an HSS 15/64" drill (0.2344 in) runs about 1,470 RPM at 90 SFM; a carbide drill about 4,890 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a 15/64" drill?

About 0.0061 in/rev in mild steel, 0.0056 in/rev in aluminum and 0.0040 in/rev in 304 stainless. At 1,470 RPM that is 8.97 IPM in steel (IPM = RPM × IPR).

What RPM for a 15/64" drill in aluminum?

4,070 RPM with HSS (250 SFM) or up to 9,780 RPM with carbide (600 SFM), feeding about 0.0056 in/rev.

What tap uses a 15/64" drill?

1/4-28 (form (roll) tap, 65% thread); 1/4-32 (form (roll) tap, 65% thread).

15/64" drill size

A 15/64" fractional drill is 0.2344 in (5.953 mm). It is the form (roll) tap, 65% thread drill for 1/4-28.

Decimal inch: 0.2344
Millimeters: 5.953
Nearest 1/64: 15/64" (+0.0000)
Type: fractional drill

Nearest equivalents in other systems

Drills closest to 15/64"
System	Drill	Inch	mm	Difference
Number / letter	Letter A	0.2340	5.944	-0.0004 in
Metric	6.0 mm	0.2362	6.000	+0.0019 in

Speeds and feeds: in mild steel an HSS drill starts at about 1,470 RPM and 0.0061 in/rev (8.97 IPM); in 6061 aluminum about 4,070 RPM.

15/64" drill speeds and feeds by material

Jobber-length twist drill, D = 0.2344 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

15/64" drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	4,070	600	9,780	0.0056	22.8	54.8
Brass / free-machining	150	2,440	400	6,520	0.0049	12.0	31.9
Low-carbon steel (1018)	90	1,470	300	4,890	0.0061	8.97	29.8
Alloy steel (4140, annealed)	70	1,140	250	4,070	0.0061	6.95	24.8
Stainless 304	40	650	150	2,440	0.0040	2.60	9.76
Gray cast iron	80	1,300	250	4,070	0.0042	5.46	17.1
Titanium 6Al-4V	25	410	100	1,630	0.0028	1.15	4.56
Plastics (acetal)	300	4,890	500	8,150	0.0041	20.1	33.4

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 1,470 RPM × 0.155 mm/rev = 228 mm/min.

Worked example: 15/64" drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.2344 ≈ 1,470 RPM.
Feed for a 0.234 in drill in mild steel ≈ 0.0061 in/rev.
IPM = 1,470 × 0.0061 = 8.97 IPM.

Peck cycle by hole depth

15/64" drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 0.703 in (17.9 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 1.172 in (29.8 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 1.875 in (47.6 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 15/64" drill

1/4-28 — form (roll) tap, 65% thread · tap speeds and feeds
1/4-32 — form (roll) tap, 65% thread

Nearest drills

Letter A: 0.2340 in / 5.944 mm (-0.0004 in)
6.0 mm: 0.2362 in / 6.000 mm (+0.0019 in)
5.9 mm: 0.2323 in / 5.900 mm (-0.0021 in)
Letter B: 0.2380 in / 6.045 mm (+0.0036 in)

Drill speed calculator, prefilled for 15/64"Drill finder: sizes near 15/64"Fractional drill chart Decimal equivalent chart

Common questions

What is a 15/64" drill in decimal and mm?: 0.2344 in, or 5.953 mm; nearest number / letter drill: Letter A (0.2340 in, -0.0004 in); nearest metric drill: 6.0 mm (0.2362 in, +0.0019 in).
What RPM for a 15/64" drill in steel?: In low-carbon steel (1018) an HSS 15/64" drill (0.2344 in) runs about 1,470 RPM at 90 SFM; a carbide drill about 4,890 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a 15/64" drill?: About 0.0061 in/rev in mild steel, 0.0056 in/rev in aluminum and 0.0040 in/rev in 304 stainless. At 1,470 RPM that is 8.97 IPM in steel (IPM = RPM × IPR).
What RPM for a 15/64" drill in aluminum?: 4,070 RPM with HSS (250 SFM) or up to 9,780 RPM with carbide (600 SFM), feeding about 0.0056 in/rev.
What tap uses a 15/64" drill?: 1/4-28 (form (roll) tap, 65% thread); 1/4-32 (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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