What is a 1/64" drill in decimal and mm?

0.0156 in, or 0.397 mm; nearest number / letter drill: #78 (0.0160 in, +0.0004 in); nearest metric drill: 0.4 mm (0.0158 in, +0.0001 in).

What RPM for a 1/64" drill in steel?

In low-carbon steel (1018) an HSS 1/64" drill (0.0156 in) runs about 22,000 RPM at 90 SFM; a carbide drill about 73,340 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a 1/64" drill?

About 0.0007 in/rev in mild steel, 0.0007 in/rev in aluminum and 0.0005 in/rev in 304 stainless. At 22,000 RPM that is 15.4 IPM in steel (IPM = RPM × IPR).

What RPM for a 1/64" drill in aluminum?

61,120 RPM with HSS (250 SFM) or up to 146,680 RPM with carbide (600 SFM), feeding about 0.0007 in/rev.

What size is a 1/64" drill?

0.0156 in / 0.397 mm. The nearest other drills are 0.4 mm (0.0158 in), #78 (0.0160 in), #79 (0.0145 in).

1/64" drill size

A 1/64" fractional drill is 0.0156 in (0.397 mm).

Decimal inch: 0.0156
Millimeters: 0.397
Nearest 1/64: 1/64" (+0.0000)
Type: fractional drill

Nearest equivalents in other systems

Drills closest to 1/64"
System	Drill	Inch	mm	Difference
Number / letter	#78	0.0160	0.406	+0.0004 in
Metric	0.4 mm	0.0158	0.400	+0.0001 in

Speeds and feeds: in mild steel an HSS drill starts at about 22,000 RPM and 0.0007 in/rev (15.4 IPM); in 6061 aluminum about 61,120 RPM.

1/64" drill speeds and feeds by material

Jobber-length twist drill, D = 0.0156 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

1/64" drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	61,120	600	146,680	0.0007	42.8	102.7
Brass / free-machining	150	36,670	400	97,780	0.0006	22.0	58.7
Low-carbon steel (1018)	90	22,000	300	73,340	0.0007	15.4	51.3
Alloy steel (4140, annealed)	70	17,110	250	61,120	0.0007	12.0	42.8
Stainless 304	40	9,780	150	36,670	0.0005	4.89	18.3
Gray cast iron	80	19,560	250	61,120	0.0005	9.78	30.6
Titanium 6Al-4V	25	6,110	100	24,450	0.0004	2.44	9.78
Plastics (acetal)	300	73,340	500	122,230	0.0013	95.3	158.9

Small drills: the computed RPM is above most spindles. Run at your spindle's maximum and keep the feed per rev; feed drops in proportion.

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 22,000 RPM × 0.018 mm/rev = 391 mm/min.

Worked example: 1/64" drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.0156 ≈ 22,000 RPM.
Feed for a 0.016 in drill in mild steel ≈ 0.0007 in/rev.
IPM = 22,000 × 0.0007 = 15.4 IPM.

Peck cycle by hole depth

1/64" drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 0.047 in (1.2 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 0.078 in (2 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 0.125 in (3.2 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 1/64" drill

No standard UNC, UNF or metric tap in our tables calls for a 1/64" drill. Use it for clearance, pilot or reamer prep holes.

Nearest drills

0.4 mm: 0.0158 in / 0.400 mm (+0.0001 in)
#78: 0.0160 in / 0.406 mm (+0.0004 in)
#79: 0.0145 in / 0.368 mm (-0.0011 in)
0.35 mm: 0.0138 in / 0.350 mm (-0.0018 in)

Drill speed calculator, prefilled for 1/64"Drill finder: sizes near 1/64"Fractional drill chart Decimal equivalent chart

Common questions

What is a 1/64" drill in decimal and mm?: 0.0156 in, or 0.397 mm; nearest number / letter drill: #78 (0.0160 in, +0.0004 in); nearest metric drill: 0.4 mm (0.0158 in, +0.0001 in).
What RPM for a 1/64" drill in steel?: In low-carbon steel (1018) an HSS 1/64" drill (0.0156 in) runs about 22,000 RPM at 90 SFM; a carbide drill about 73,340 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a 1/64" drill?: About 0.0007 in/rev in mild steel, 0.0007 in/rev in aluminum and 0.0005 in/rev in 304 stainless. At 22,000 RPM that is 15.4 IPM in steel (IPM = RPM × IPR).
What RPM for a 1/64" drill in aluminum?: 61,120 RPM with HSS (250 SFM) or up to 146,680 RPM with carbide (600 SFM), feeding about 0.0007 in/rev.
What size is a 1/64" drill?: 0.0156 in / 0.397 mm. The nearest other drills are 0.4 mm (0.0158 in), #78 (0.0160 in), #79 (0.0145 in).

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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