Every edge distance and spacing is measured from the hole centre. Slotted holes need more edge distance than the value shown — the edge card says how.
Pick a bolt diameter and the thickness of the thinner connected part, and you get the hole sizes, the minimum edge distance, the minimum and preferred spacing, and the two maximums that depend on thickness. Each answer shows the arithmetic and names the AISC 360 section it comes from, so it can be checked rather than trusted.
| Answer | Rule used | Section |
|---|---|---|
| Standard hole | d + 1/16 below 1" diameter; d + 1/8 at 1" and larger | Table J3.3 |
| Oversized hole | d + 1/8 at 1/2"; d + 3/16 from 5/8" to 7/8"; d + 1/4 at 1"; d + 5/16 at 1 1/8" and larger | Table J3.3 |
| Short-slot | standard width (so it widens at 1" too); length d + 3/16 at 1/2", d + 1/4 from 5/8" to 7/8", d + 5/16 at 1", d + 3/8 above | Table J3.3 |
| Long-slot | standard width; length 2.5 d | Table J3.3 |
| Minimum edge distance | the tabulated value for the diameter; 1.25 d above 1 1/4" | Table J3.4 |
| Maximum edge distance | 12 t, but never more than 6" | J3.5 |
| Minimum spacing | 2 2/3 d, rounded up to the next 1/16 | J3.3 |
| Preferred spacing | 3 d | J3.3 |
| Maximum spacing, painted or not subject to corrosion | 24 t, but never more than 12" | J3.5 |
| Maximum spacing, unpainted weathering steel | 14 t, but never more than 7" | J3.5 |
The 2020 RCSC Specification widened the standard hole for bolts 1 in. and larger, from d + 1/16 to d + 1/8. A 1" bolt now takes a 1 1/8" standard hole, and the short- and long-slot widths widened with it. The change is carried into AISC 360-22 and the 16th Edition Manual, which bundles that RCSC Specification as Part 16.2. A chart printed before it shows 1 1/16", and plenty of them are still pinned above desks. If your shop standard says 1 1/16" for a 1" bolt, it predates the 2020 revision — that is a conversation with your fabricator, not a typo on this page.
The values here were checked against the RCSC Specification for Structural Joints Using High-Strength Bolts (June 11, 2020), Table 3.1 — the primary document AISC's Table J3.3 mirrors — and its commentary, which states the clearance increase for 1-in.-and-larger bolts in as many words.
Standard hole 13/16" — bolt diameter plus 1/16" for bolts under 1" (AISC 360 Table J3.3). Oversized 15/16". Short slot 13/16" × 1". Long slot 13/16" × 1 7/8", the length being 2.5 times the diameter.
1", the tabulated value in AISC 360 Table J3.4, measured from the hole centre. Above 1 1/4" diameter the minimum is 1.25 times the diameter. A slotted hole needs more edge distance than the tabulated value, measured to the end of the slot.
2 2/3 times the diameter, centre to centre, with 3 times the diameter preferred (AISC 360 J3.3). For a 3/4" bolt that is 2" minimum and 2 1/4" preferred.
Yes. The 2020 RCSC Specification, carried into AISC 360-22 Table J3.3, widened the standard hole for bolts 1" and larger from diameter plus 1/16" to diameter plus 1/8". A 1" bolt now takes a 1 1/8" standard hole; a chart that says 1 1/16" predates the revision.
Maximum edge distance is 12 times the thickness of the thinner connected part, but never more than 6". Maximum spacing is 24 times that thickness, not over 12", for painted members or members not subject to corrosion; 14 times the thickness, not over 7", for unpainted weathering steel. AISC 360 J3.5.
The one everybody knows: a 3/4" bolt gets a 13/16" standard hole, 1" minimum edge distance, and 2 1/4" preferred spacing. If this page ever says otherwise, do not use it — tell us.