What is a 20.0 mm drill in decimal and mm?

0.7874 in, or 20.000 mm; nearest fractional drill: 25/32" (0.7813 in, -0.0062 in); nearest number / letter drill: Letter Z (0.4130 in, -0.3744 in).

What RPM for a 20.0 mm drill in steel?

In low-carbon steel (1018) an HSS 20.0 mm drill (0.7874 in) runs about 440 RPM at 90 SFM; a carbide drill about 1,460 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a 20.0 mm drill?

About 0.0116 in/rev in mild steel, 0.0113 in/rev in aluminum and 0.0096 in/rev in 304 stainless. At 440 RPM that is 5.10 IPM in steel (IPM = RPM × IPR).

What RPM for a 20.0 mm drill in aluminum?

1,210 RPM with HSS (250 SFM) or up to 2,910 RPM with carbide (600 SFM), feeding about 0.0113 in/rev.

What size is a 20.0 mm drill?

0.7874 in / 20.00 mm. The nearest other drills are 25/32" (0.7813 in), 51/64" (0.7969 in), 19.75 mm (0.7776 in).

20.0 mm drill size

A 20.0 mm metric drill is 0.7874 in (20.000 mm).

Decimal inch: 0.7874
Millimeters: 20.000
Nearest 1/64: 25/32" (+0.0061)
Type: metric drill

Nearest equivalents in other systems

Drills closest to 20.0 mm
System	Drill	Inch	mm	Difference
Fractional	25/32"	0.7813	19.844	-0.0062 in
Number / letter	Letter Z	0.4130	10.490	-0.3744 in

Speeds and feeds: in mild steel an HSS drill starts at about 440 RPM and 0.0116 in/rev (5.10 IPM); in 6061 aluminum about 1,210 RPM.

20.0 mm drill speeds and feeds by material

Jobber-length twist drill, D = 0.7874 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

20.0 mm drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	1,210	600	2,910	0.0113	13.7	32.9
Brass / free-machining	150	730	400	1,940	0.0091	6.64	17.6
Low-carbon steel (1018)	90	440	300	1,460	0.0116	5.10	16.9
Alloy steel (4140, annealed)	70	340	250	1,210	0.0121	4.11	14.6
Stainless 304	40	190	150	730	0.0096	1.82	7.01
Gray cast iron	80	390	250	1,210	0.0101	3.94	12.2
Titanium 6Al-4V	25	120	100	490	0.0056	0.67	2.74
Plastics (acetal)	300	1,460	500	2,430	0.0071	10.4	17.3

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 440 RPM × 0.295 mm/rev = 130 mm/min.

Worked example: 20.0 mm drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.7874 ≈ 440 RPM.
Feed for a 0.787 in drill in mild steel ≈ 0.0116 in/rev.
IPM = 440 × 0.0116 = 5.10 IPM.

Peck cycle by hole depth

20.0 mm drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 2.362 in (60 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 3.937 in (100 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 6.299 in (160 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 20.0 mm drill

No standard UNC, UNF or metric tap in our tables calls for a 20.0 mm drill. Use it for clearance, pilot or reamer prep holes.

Nearest drills

25/32": 0.7813 in / 19.844 mm (-0.0062 in)
51/64": 0.7969 in / 20.241 mm (+0.0095 in)
19.75 mm: 0.7776 in / 19.750 mm (-0.0098 in)
20.25 mm: 0.7972 in / 20.250 mm (+0.0098 in)

Drill speed calculator, prefilled for 20.0 mm Drill finder: sizes near 20.0 mm Metric drill chart Decimal equivalent chart

Common questions

What is a 20.0 mm drill in decimal and mm?: 0.7874 in, or 20.000 mm; nearest fractional drill: 25/32" (0.7813 in, -0.0062 in); nearest number / letter drill: Letter Z (0.4130 in, -0.3744 in).
What RPM for a 20.0 mm drill in steel?: In low-carbon steel (1018) an HSS 20.0 mm drill (0.7874 in) runs about 440 RPM at 90 SFM; a carbide drill about 1,460 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a 20.0 mm drill?: About 0.0116 in/rev in mild steel, 0.0113 in/rev in aluminum and 0.0096 in/rev in 304 stainless. At 440 RPM that is 5.10 IPM in steel (IPM = RPM × IPR).
What RPM for a 20.0 mm drill in aluminum?: 1,210 RPM with HSS (250 SFM) or up to 2,910 RPM with carbide (600 SFM), feeding about 0.0113 in/rev.
What size is a 20.0 mm drill?: 0.7874 in / 20.00 mm. The nearest other drills are 25/32" (0.7813 in), 51/64" (0.7969 in), 19.75 mm (0.7776 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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