What is a 57/64" drill in decimal and mm?

0.8906 in, or 22.622 mm; nearest number / letter drill: Letter Z (0.4130 in, -0.4776 in); nearest metric drill: 22.5 mm (0.8858 in, -0.0048 in).

What RPM for a 57/64" drill in steel?

In low-carbon steel (1018) an HSS 57/64" drill (0.8906 in) runs about 390 RPM at 90 SFM; a carbide drill about 1,290 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a 57/64" drill?

About 0.0121 in/rev in mild steel, 0.0121 in/rev in aluminum and 0.0101 in/rev in 304 stainless. At 390 RPM that is 4.72 IPM in steel (IPM = RPM × IPR).

What RPM for a 57/64" drill in aluminum?

1,070 RPM with HSS (250 SFM) or up to 2,570 RPM with carbide (600 SFM), feeding about 0.0121 in/rev.

What tap uses a 57/64" drill?

15/16-20 (cut tap, 75% thread); 7/8-9 (Helicoil / STI insert (7/8-9×1D)).

57/64" drill size

A 57/64" fractional drill is 0.8906 in (22.622 mm). It is the cut tap, 75% thread drill for 15/16-20.

Decimal inch: 0.8906
Millimeters: 22.622
Nearest 1/64: 57/64" (+0.0000)
Type: fractional drill

Nearest equivalents in other systems

Drills closest to 57/64"
System	Drill	Inch	mm	Difference
Number / letter	Letter Z	0.4130	10.490	-0.4776 in
Metric	22.5 mm	0.8858	22.500	-0.0048 in

Speeds and feeds: in mild steel an HSS drill starts at about 390 RPM and 0.0121 in/rev (4.72 IPM); in 6061 aluminum about 1,070 RPM.

57/64" drill speeds and feeds by material

Jobber-length twist drill, D = 0.8906 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

57/64" drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	1,070	600	2,570	0.0121	12.9	31.1
Brass / free-machining	150	640	400	1,720	0.0096	6.14	16.5
Low-carbon steel (1018)	90	390	300	1,290	0.0121	4.72	15.6
Alloy steel (4140, annealed)	70	300	250	1,070	0.0126	3.78	13.5
Stainless 304	40	170	150	640	0.0101	1.72	6.46
Gray cast iron	80	340	250	1,070	0.0106	3.60	11.3
Titanium 6Al-4V	25	110	100	430	0.0058	0.64	2.49
Plastics (acetal)	300	1,290	500	2,140	0.0076	9.80	16.3

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 390 RPM × 0.307 mm/rev = 120 mm/min.

Worked example: 57/64" drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.8906 ≈ 390 RPM.
Feed for a 0.891 in drill in mild steel ≈ 0.0121 in/rev.
IPM = 390 × 0.0121 = 4.72 IPM.

Peck cycle by hole depth

57/64" drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 2.672 in (67.9 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 4.453 in (113.1 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 7.125 in (181 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 57/64" drill

15/16-20 — cut tap, 75% thread
7/8-9 — Helicoil / STI insert (7/8-9×1D) · tap speeds and feeds

Nearest drills

22.5 mm: 0.8858 in / 22.500 mm (-0.0048 in)
22.75 mm: 0.8957 in / 22.750 mm (+0.0050 in)
22.25 mm: 0.8760 in / 22.250 mm (-0.0146 in)
23.0 mm: 0.9055 in / 23.000 mm (+0.0149 in)

Drill speed calculator, prefilled for 57/64"Drill finder: sizes near 57/64"Fractional drill chart Decimal equivalent chart

Common questions

What is a 57/64" drill in decimal and mm?: 0.8906 in, or 22.622 mm; nearest number / letter drill: Letter Z (0.4130 in, -0.4776 in); nearest metric drill: 22.5 mm (0.8858 in, -0.0048 in).
What RPM for a 57/64" drill in steel?: In low-carbon steel (1018) an HSS 57/64" drill (0.8906 in) runs about 390 RPM at 90 SFM; a carbide drill about 1,290 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a 57/64" drill?: About 0.0121 in/rev in mild steel, 0.0121 in/rev in aluminum and 0.0101 in/rev in 304 stainless. At 390 RPM that is 4.72 IPM in steel (IPM = RPM × IPR).
What RPM for a 57/64" drill in aluminum?: 1,070 RPM with HSS (250 SFM) or up to 2,570 RPM with carbide (600 SFM), feeding about 0.0121 in/rev.
What tap uses a 57/64" drill?: 15/16-20 (cut tap, 75% thread); 7/8-9 (Helicoil / STI insert (7/8-9×1D)).

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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