What is a 5/8" drill in decimal and mm?

0.6250 in, or 15.875 mm; nearest number / letter drill: Letter Z (0.4130 in, -0.2120 in); nearest metric drill: 15.75 mm (0.6201 in, -0.0049 in).

What RPM for a 5/8" drill in steel?

In low-carbon steel (1018) an HSS 5/8" drill (0.6250 in) runs about 550 RPM at 90 SFM; a carbide drill about 1,830 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a 5/8" drill?

About 0.0110 in/rev in mild steel, 0.0105 in/rev in aluminum and 0.0090 in/rev in 304 stainless. At 550 RPM that is 6.05 IPM in steel (IPM = RPM × IPR).

What RPM for a 5/8" drill in aluminum?

1,530 RPM with HSS (250 SFM) or up to 3,670 RPM with carbide (600 SFM), feeding about 0.0105 in/rev.

What size is a 5/8" drill?

0.6250 in / 15.88 mm. The nearest other drills are 15.75 mm (0.6201 in), 16.0 mm (0.6299 in), 15.5 mm (0.6102 in).

5/8" drill size

A 5/8" fractional drill is 0.6250 in (15.875 mm).

Decimal inch: 0.6250
Millimeters: 15.875
Nearest 1/64: 5/8" (+0.0000)
Type: fractional drill

Nearest equivalents in other systems

Drills closest to 5/8"
System	Drill	Inch	mm	Difference
Number / letter	Letter Z	0.4130	10.490	-0.2120 in
Metric	15.75 mm	0.6201	15.750	-0.0049 in

Speeds and feeds: in mild steel an HSS drill starts at about 550 RPM and 0.0110 in/rev (6.05 IPM); in 6061 aluminum about 1,530 RPM.

5/8" drill speeds and feeds by material

Jobber-length twist drill, D = 0.6250 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

5/8" drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	1,530	600	3,670	0.0105	16.1	38.5
Brass / free-machining	150	920	400	2,440	0.0086	7.91	21.0
Low-carbon steel (1018)	90	550	300	1,830	0.0110	6.05	20.1
Alloy steel (4140, annealed)	70	430	250	1,530	0.0118	5.07	18.1
Stainless 304	40	240	150	920	0.0090	2.16	8.28
Gray cast iron	80	490	250	1,530	0.0093	4.56	14.2
Titanium 6Al-4V	25	150	100	610	0.0053	0.80	3.23
Plastics (acetal)	300	1,830	500	3,060	0.0065	11.9	19.9

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 550 RPM × 0.279 mm/rev = 154 mm/min.

Worked example: 5/8" drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.6250 ≈ 550 RPM.
Feed for a 0.625 in drill in mild steel ≈ 0.0110 in/rev.
IPM = 550 × 0.0110 = 6.05 IPM.

Peck cycle by hole depth

5/8" drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 1.875 in (47.6 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 3.125 in (79.4 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 5.000 in (127 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 5/8" drill

No standard UNC, UNF or metric tap in our tables calls for a 5/8" drill. Use it for clearance, pilot or reamer prep holes.

Nearest drills

15.75 mm: 0.6201 in / 15.750 mm (-0.0049 in)
16.0 mm: 0.6299 in / 16.000 mm (+0.0049 in)
15.5 mm: 0.6102 in / 15.500 mm (-0.0148 in)
16.25 mm: 0.6398 in / 16.250 mm (+0.0148 in)

Drill speed calculator, prefilled for 5/8"Drill finder: sizes near 5/8"Fractional drill chart Decimal equivalent chart

Common questions

What is a 5/8" drill in decimal and mm?: 0.6250 in, or 15.875 mm; nearest number / letter drill: Letter Z (0.4130 in, -0.2120 in); nearest metric drill: 15.75 mm (0.6201 in, -0.0049 in).
What RPM for a 5/8" drill in steel?: In low-carbon steel (1018) an HSS 5/8" drill (0.6250 in) runs about 550 RPM at 90 SFM; a carbide drill about 1,830 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a 5/8" drill?: About 0.0110 in/rev in mild steel, 0.0105 in/rev in aluminum and 0.0090 in/rev in 304 stainless. At 550 RPM that is 6.05 IPM in steel (IPM = RPM × IPR).
What RPM for a 5/8" drill in aluminum?: 1,530 RPM with HSS (250 SFM) or up to 3,670 RPM with carbide (600 SFM), feeding about 0.0105 in/rev.
What size is a 5/8" drill?: 0.6250 in / 15.88 mm. The nearest other drills are 15.75 mm (0.6201 in), 16.0 mm (0.6299 in), 15.5 mm (0.6102 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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