Dimensions, drill sizes and wrench sizes for 5/8-24 UNEF.
Designation
5/8-24 UNEF
Major (outside) diameter
15.875 mm · 0.625"
Pitch
1.058 mm · 24 TPI
Pitch diameter
15.188 mm · 0.5979"
Minor diameter (external)
14.577 mm · 0.5739"
Minor diameter (internal)
14.729 mm · 0.5799"
Recommended tap drill
37/64" · 14.68 mm · ≈87% thread
Clearance hole
Close 41/64" · Normal 21/32" · Loose 11/16" - nominal + 1/64" / 1/32" / 1/16" to the nearest standard drill (common shop practice).
Hex head (across flats)
15/16"
Socket key (across flats)
1/2"
Close 41/64" · Normal 21/32" · Loose 11/16" - nominal + 1/64" / 1/32" / 1/16" to the nearest standard drill (common shop practice).
5/8-24 UNEF in numbers
5/8-24 UNEF is 0.6250 in across the crests with 24 threads per inch, a 1.058 mm pitch. The basic pitch diameter is 15.188 mm and the bolt's minor diameter 14.577 mm, so the thread is 0.649 mm deep on the bolt. Its tensile stress area is 0.2682 in², 19% more than the coarser 5/8-11 UNC at the same diameter. The nearest metric size, M16 × 2.0, is 0.13 mm larger across the crests and its pitch is 0.942 mm coarser, so the two do not interchange.
Tap drill by thread percentage
Hole = D − % × 0.0129904 × P, with D = 15.875 mm and P = 1.058 mm. A smaller hole leaves more thread; the recommended 37/64" drill above gives about 87%.
Tap-drill hole diameters for 5/8-24 UNEF at several thread percentages.
Thread
Hole (mm)
Hole (in)
Nearest drill
60%
15.05
0.5925
19/32" (0.5938 in) gives 58%
65%
14.98
0.5898
19/32" (0.5938 in) gives 58%
70%
14.91
0.5871
19/32" (0.5938 in) gives 58%
75%
14.84
0.5844
37/64" (0.5781 in) gives 87%
Tightening torque estimate
Target preload is 75% of proof load; torque is estimated from T = K · F · d.
Proof-load preload and estimated tightening torque for 5/8-24 UNEF by fastener grade or property class.
Grade / class
Stress area
Preload
Torque
SAE Grade 2
0.2682 in²
11065 lbf
115 lb·ft · 1383 lb·in
SAE Grade 5
0.2682 in²
17100 lbf
178 lb·ft · 2138 lb·in
SAE Grade 8
0.2682 in²
24141 lbf
251 lb·ft · 3018 lb·in
Strengths are SAE J429 for this diameter band. J429 steps down with size: Grade 2 falls to 33 ksi proof above 3/4 in and Grade 5 to 74 ksi above 1 in, so these figures are not the small-size values. The Grade 2 row applies to bolts up to 6 in long; a longer Grade 2 bolt of the same diameter drops to 33 ksi proof.
These figures assume a nut factor of K = 0.20 (dry / as-received steel). K captures thread and head friction and can swing torque by 30% or more - a lubricated joint needs noticeably less. Change the lubrication assumption in the bolt-torque calculator.
Put 5/8-24 UNEF on a job sheet
The bolt schedule collects the fasteners for one job onto a single sheet - tap drill, wrench size, grade and tightening torque on every line, taken straight from pages like this one. Free schedules hold 3 lines and are saved in this browser only.
For a 5/8-24 UNEF thread, drill the hole with a 37/64" tap drill (14.68 mm) before tapping. That produces roughly 87% thread engagement, the usual target for a strong, tappable hole. The mating bolt has a major diameter of 15.875 mm and a pitch of 1.058 mm (24 TPI).
To pass a 5/8-24 UNEF bolt through a part rather than thread it, use a clearance hole: Close 41/64" · Normal 21/32" · Loose 11/16" - nominal + 1/64" / 1/32" / 1/16" to the nearest standard drill (common shop practice)..
All values come from the standard thread formulas (ISO 68-1 / ASME B1.1) and published standard tables. See the full reference.
Frequently asked questions
What drill size do I need to tap a 5/8-24 UNEF thread?
Drill 37/64" (14.68 mm) before tapping 5/8-24 UNEF. That leaves roughly 87% thread engagement, the usual target for a strong hole that still taps cleanly.
Is 5/8-24 UNEF a coarse or fine thread?
5/8-24 UNEF is a Unified extra-fine (UNEF) thread at 24 threads per inch, used for thin-wall parts, short thread engagement and fine adjustment.
What size clearance hole does a 5/8-24 UNEF bolt need?
Close 41/64" · Normal 21/32" · Loose 11/16" - nominal + 1/64" / 1/32" / 1/16" to the nearest standard drill (common shop practice). A clearance hole lets the 5/8-24 UNEF bolt pass through the part instead of threading into it.
How much torque should I use on a 5/8-24 UNEF bolt?
Estimated tightening torque for 5/8-24 UNEF runs from 115 lb·ft (SAE Grade 2) to 251 lb·ft (SAE Grade 8), targeting 75% of proof load with a dry nut factor of K = 0.20. Lubricated threads need noticeably less torque.
Nearest standard metric sizes by major diameter. These are substitutes by size only - the thread forms are not interchangeable, so never run one into the other.