Dimensions, drill sizes and wrench sizes for 5/8-11 UNC.
Designation
5/8-11 UNC
Major (outside) diameter
15.875 mm · 0.625"
Pitch
2.309 mm · 11 TPI
Pitch diameter
14.375 mm · 0.566"
Minor diameter (external)
13.042 mm · 0.5135"
Minor diameter (internal)
13.375 mm · 0.5266"
Recommended tap drill
17/32" · 13.49 mm · ≈79% 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).
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 5/8-11 UNC by fastener grade or property class.
Grade / class
Stress area
Preload
Torque
SAE Grade 2
0.226 in²
9323 lbf
97 lb·ft · 1165 lb·in
SAE Grade 5
0.226 in²
14408 lbf
150 lb·ft · 1801 lb·in
SAE Grade 8
0.226 in²
20340 lbf
212 lb·ft · 2543 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 5/8-11 UNC 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 5/8-11 UNC thread, drill the hole with a 17/32" tap drill (13.49 mm) before tapping. That produces roughly 79% 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 2.309 mm (11 TPI).
To pass a 5/8-11 UNC 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 are generated from the standard thread formulas (ISO 68-1 / ASME B1.1) and published standard tables - not hand-entered. See the full reference.
Frequently asked questions
What drill size do I need to tap a 5/8-11 UNC thread?
Drill 17/32" (13.49 mm) before tapping 5/8-11 UNC. That leaves roughly 79% thread engagement, the usual target for a strong hole that still taps cleanly.
Is 5/8-11 UNC a coarse or fine thread?
5/8-11 UNC is a Unified coarse (UNC) thread at 11 threads per inch, the default inch series for general fastening in this diameter.
What size clearance hole does a 5/8-11 UNC 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 5/8-11 UNC bolt pass through the part instead of threading into it.
How much torque should I use on a 5/8-11 UNC bolt?
Estimated tightening torque for 5/8-11 UNC runs from 97 lb·ft (SAE Grade 2) to 212 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.