What is a 49/64" drill in decimal and mm?

0.7656 in, or 19.447 mm; nearest number / letter drill: Letter Z (0.4130 in, -0.3526 in); nearest metric drill: 19.5 mm (0.7677 in, +0.0021 in).

What RPM for a 49/64" drill in steel?

In low-carbon steel (1018) an HSS 49/64" drill (0.7656 in) runs about 450 RPM at 90 SFM; a carbide drill about 1,500 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a 49/64" drill?

About 0.0116 in/rev in mild steel, 0.0111 in/rev in aluminum and 0.0096 in/rev in 304 stainless. At 450 RPM that is 5.22 IPM in steel (IPM = RPM × IPR).

What RPM for a 49/64" drill in aluminum?

1,250 RPM with HSS (250 SFM) or up to 2,990 RPM with carbide (600 SFM), feeding about 0.0111 in/rev.

What tap uses a 49/64" drill?

7/8-9 (cut tap, 75% thread); 13/16-20 (cut tap, 75% thread); 3/4-10 (Helicoil / STI insert (3/4-10×1D)).

49/64" drill size

A 49/64" fractional drill is 0.7656 in (19.447 mm). It is the cut tap, 75% thread drill for 7/8-9.

Decimal inch: 0.7656
Millimeters: 19.447
Nearest 1/64: 49/64" (+0.0000)
Type: fractional drill

Nearest equivalents in other systems

Drills closest to 49/64"
System	Drill	Inch	mm	Difference
Number / letter	Letter Z	0.4130	10.490	-0.3526 in
Metric	19.5 mm	0.7677	19.500	+0.0021 in

Speeds and feeds: in mild steel an HSS drill starts at about 450 RPM and 0.0116 in/rev (5.22 IPM); in 6061 aluminum about 1,250 RPM.

49/64" drill speeds and feeds by material

Jobber-length twist drill, D = 0.7656 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

49/64" drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	1,250	600	2,990	0.0111	13.9	33.2
Brass / free-machining	150	750	400	2,000	0.0091	6.83	18.2
Low-carbon steel (1018)	90	450	300	1,500	0.0116	5.22	17.4
Alloy steel (4140, annealed)	70	350	250	1,250	0.0121	4.23	15.1
Stainless 304	40	200	150	750	0.0096	1.92	7.20
Gray cast iron	80	400	250	1,250	0.0101	4.04	12.6
Titanium 6Al-4V	25	120	100	500	0.0055	0.66	2.75
Plastics (acetal)	300	1,500	500	2,490	0.0071	10.7	17.7

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 450 RPM × 0.295 mm/rev = 133 mm/min.

Worked example: 49/64" drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.7656 ≈ 450 RPM.
Feed for a 0.766 in drill in mild steel ≈ 0.0116 in/rev.
IPM = 450 × 0.0116 = 5.22 IPM.

Peck cycle by hole depth

49/64" drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 2.297 in (58.3 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 3.828 in (97.2 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 6.125 in (155.6 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 49/64" drill

7/8-9 — cut tap, 75% thread · tap speeds and feeds
13/16-20 — cut tap, 75% thread
3/4-10 — Helicoil / STI insert (3/4-10×1D) · tap speeds and feeds

Nearest drills

19.5 mm: 0.7677 in / 19.500 mm (+0.0021 in)
19.25 mm: 0.7579 in / 19.250 mm (-0.0077 in)
19.75 mm: 0.7776 in / 19.750 mm (+0.0119 in)
3/4": 0.7500 in / 19.050 mm (-0.0156 in)

Drill speed calculator, prefilled for 49/64"Drill finder: sizes near 49/64"Fractional drill chart Decimal equivalent chart

Common questions

What is a 49/64" drill in decimal and mm?: 0.7656 in, or 19.447 mm; nearest number / letter drill: Letter Z (0.4130 in, -0.3526 in); nearest metric drill: 19.5 mm (0.7677 in, +0.0021 in).
What RPM for a 49/64" drill in steel?: In low-carbon steel (1018) an HSS 49/64" drill (0.7656 in) runs about 450 RPM at 90 SFM; a carbide drill about 1,500 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a 49/64" drill?: About 0.0116 in/rev in mild steel, 0.0111 in/rev in aluminum and 0.0096 in/rev in 304 stainless. At 450 RPM that is 5.22 IPM in steel (IPM = RPM × IPR).
What RPM for a 49/64" drill in aluminum?: 1,250 RPM with HSS (250 SFM) or up to 2,990 RPM with carbide (600 SFM), feeding about 0.0111 in/rev.
What tap uses a 49/64" drill?: 7/8-9 (cut tap, 75% thread); 13/16-20 (cut tap, 75% thread); 3/4-10 (Helicoil / STI insert (3/4-10×1D)).

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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