What is a 29/64" drill in decimal and mm?

0.4531 in, or 11.509 mm; nearest number / letter drill: Letter Z (0.4130 in, -0.0401 in); nearest metric drill: 11.5 mm (0.4528 in, -0.0004 in).

What RPM for a 29/64" drill in steel?

In low-carbon steel (1018) an HSS 29/64" drill (0.4531 in) runs about 760 RPM at 90 SFM; a carbide drill about 2,530 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.

What feed for a 29/64" drill?

About 0.0101 in/rev in mild steel, 0.0094 in/rev in aluminum and 0.0077 in/rev in 304 stainless. At 760 RPM that is 7.68 IPM in steel (IPM = RPM × IPR).

What RPM for a 29/64" drill in aluminum?

2,110 RPM with HSS (250 SFM) or up to 5,060 RPM with carbide (600 SFM), feeding about 0.0094 in/rev.

What tap uses a 29/64" drill?

1/2-20 (cut tap, 75% thread); 1/2-13 (cut tap, 50% thread); 7/16-14 (Helicoil / STI insert (7/16-14×1D)).

29/64" drill size

A 29/64" fractional drill is 0.4531 in (11.509 mm). It is the cut tap, 75% thread drill for 1/2-20.

Decimal inch: 0.4531
Millimeters: 11.509
Nearest 1/64: 29/64" (+0.0000)
Type: fractional drill

Nearest equivalents in other systems

Drills closest to 29/64"
System	Drill	Inch	mm	Difference
Number / letter	Letter Z	0.4130	10.490	-0.0401 in
Metric	11.5 mm	0.4528	11.500	-0.0004 in

Speeds and feeds: in mild steel an HSS drill starts at about 760 RPM and 0.0101 in/rev (7.68 IPM); in 6061 aluminum about 2,110 RPM.

29/64" drill speeds and feeds by material

Jobber-length twist drill, D = 0.4531 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

29/64" drilling speeds
Material	HSS SFM	HSS RPM	Carbide SFM	Carbide RPM	Feed (in/rev)	HSS IPM	Carbide IPM
Aluminum (6061)	250	2,110	600	5,060	0.0094	19.8	47.6
Brass / free-machining	150	1,260	400	3,370	0.0075	9.45	25.3
Low-carbon steel (1018)	90	760	300	2,530	0.0101	7.68	25.6
Alloy steel (4140, annealed)	70	590	250	2,110	0.0111	6.55	23.4
Stainless 304	40	340	150	1,260	0.0077	2.62	9.70
Gray cast iron	80	670	250	2,110	0.0078	5.23	16.5
Titanium 6Al-4V	25	210	100	840	0.0047	0.99	3.95
Plastics (acetal)	300	2,530	500	4,210	0.0056	14.2	23.6

Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 760 RPM × 0.257 mm/rev = 195 mm/min.

Worked example: 29/64" drill in 1018 steel

HSS drill in low-carbon steel: 90 SFM.
RPM = 3.82 × 90 ÷ 0.4531 ≈ 760 RPM.
Feed for a 0.453 in drill in mild steel ≈ 0.0101 in/rev.
IPM = 760 × 0.0101 = 7.68 IPM.

Peck cycle by hole depth

29/64" drill: depth and canned cycle
Depth	Cycle	Peck	Note
3×D = 1.359 in (34.5 mm)	G81 (no peck)	None	Up to 3×D a sharp drill clears chips on its own.
5×D = 2.266 in (57.5 mm)	G73 chip-break	1 × D	Chip-break pecks; full retract if chips pack (soft aluminum, stainless).
8×D = 3.625 in (92.1 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 29/64" drill

1/2-20 — cut tap, 75% thread · tap speeds and feeds
1/2-13 — cut tap, 50% thread · tap speeds and feeds
7/16-14 — Helicoil / STI insert (7/16-14×1D) · tap speeds and feeds

Nearest drills

11.5 mm: 0.4528 in / 11.500 mm (-0.0004 in)
11.6 mm: 0.4567 in / 11.600 mm (+0.0036 in)
11.4 mm: 0.4488 in / 11.400 mm (-0.0043 in)
11.7 mm: 0.4606 in / 11.700 mm (+0.0075 in)

Drill speed calculator, prefilled for 29/64"Drill finder: sizes near 29/64"Fractional drill chart Decimal equivalent chart

Common questions

What is a 29/64" drill in decimal and mm?: 0.4531 in, or 11.509 mm; nearest number / letter drill: Letter Z (0.4130 in, -0.0401 in); nearest metric drill: 11.5 mm (0.4528 in, -0.0004 in).
What RPM for a 29/64" drill in steel?: In low-carbon steel (1018) an HSS 29/64" drill (0.4531 in) runs about 760 RPM at 90 SFM; a carbide drill about 2,530 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
What feed for a 29/64" drill?: About 0.0101 in/rev in mild steel, 0.0094 in/rev in aluminum and 0.0077 in/rev in 304 stainless. At 760 RPM that is 7.68 IPM in steel (IPM = RPM × IPR).
What RPM for a 29/64" drill in aluminum?: 2,110 RPM with HSS (250 SFM) or up to 5,060 RPM with carbide (600 SFM), feeding about 0.0094 in/rev.
What tap uses a 29/64" drill?: 1/2-20 (cut tap, 75% thread); 1/2-13 (cut tap, 50% thread); 7/16-14 (Helicoil / STI insert (7/16-14×1D)).

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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