AISC Standard Hole Sizes — Table J3.3 Reference

AISC 360-22 Table J3.3 defines four bolt hole types: standard (STD), oversized (OVS), short-slotted (SSL), and long-slotted (LSL). Each type serves a specific purpose in steel connection design — standard holes are the default for most connections, oversized holes provide field fit-up tolerance in slip-critical joints, and slotted holes accommodate movement or alignment adjustment. Choosing the wrong hole type can reduce connection capacity or violate code requirements.

This page reproduces the complete Table J3.3 dimensions, explains when to use each type, and covers the net area and slip resistance implications.

Quick access:

• Complete Hole Size Table
• Standard Holes (STD)
• Oversized Holes (OVS)
• Short-Slotted Holes (SSL)
• Long-Slotted Holes (LSL)
• Net Area Deductions
• Slip Resistance Factors by Hole Type
• Hole Type Selection Guide
• Frequently Asked Questions

Complete AISC 360-22 Table J3.3 — Bolt Hole Dimensions

All dimensions in inches. Slot dimensions are width x length.

Pattern for bolts larger than 1-1/8":

• Standard: d + 1/16"
• Oversized: d + 5/16"
• Short-slot width: d + 1/16", length: d + 3/8"
• Long-slot width: d + 1/16", length: 2.5d

Most searched value: A 3/4" bolt uses a standard hole of 13/16" (0.8125").

Standard Holes (STD) — Default for Most Connections

Standard holes provide the minimum clearance needed for bolt installation under normal erection conditions. The standard clearance is 1/16" larger than the bolt diameter.

When to Use Standard Holes

• All bearing-type connections — the bolt bears against the hole; standard holes minimize play
• Slip-critical connections — standard holes give the highest slip resistance factor
• Tension members — standard holes minimize the net area deduction, maximizing tension capacity
• Default for all connections unless a specific reason requires a different type

Standard Hole Clearance

The 1/32" per-side clearance is tight — field erection with standard holes requires relatively accurate fabrication. This is by design: standard holes are intended for normal conditions where fabrication tolerances are met.

Oversized Holes (OVS) — Field Fit-Up Tolerance

Oversized holes provide 5/16" additional clearance beyond the bolt diameter (compared to 1/16" for standard holes). This extra tolerance helps when accumulated fabrication and erection tolerances make standard holes impractical.

When to Use Oversized Holes

• Slip-critical connections requiring field adjustment — multi-story frames where column plumbness tolerances accumulate
• Base plates with anchor rods — oversized holes in base plates allow adjustment during erection (though base plates follow different rules per AISC Design Guide 1)
• Long-span trusses — accumulated length tolerances can exceed standard hole clearance

Restrictions

• NOT permitted in bearing-type connections (AISC 360 Section J3.2) — the bolt would need to travel further before engaging bearing, and the connection would deform excessively
• Restricted to slip-critical connections only
• Plate washers required when oversized holes appear in an outer ply — the washer covers the excess hole area and transfers the clamping force to the connected material
• Reduced slip resistance — apply hole type factor h_sc = 0.85 (see table below)

Short-Slotted Holes (SSL) — One-Direction Adjustment

Short-slotted holes have the same width as standard holes but add a slot in one direction. The slot length is approximately d + 1/4" (one bolt diameter plus 1/4" clearance).

When to Use Short-Slotted Holes

• Beam web connections — to accommodate beam camber and length tolerances. The slot is oriented parallel to the beam axis.
• Connections requiring one-direction adjustment — e.g., thermal movement in one direction only
• HSS connections — to accommodate fit-up between the HSS wall and gusset plate

Orientation Rules

The orientation of the slot relative to the direction of load affects the slip resistance:

Example: A beam web connection with short-slotted holes oriented vertically (parallel to the beam axis, perpendicular to the horizontal shear load) uses h_sc = 1.0. If the slot is oriented horizontally (parallel to the shear load), h_sc = 0.85.

Bearing-Type Connections

Short-slotted holes are permitted in bearing-type connections only if the slot is perpendicular to the direction of load. If the slot is parallel to the load, the bolt may not engage bearing properly, and the connection must be slip-critical.

Long-Slotted Holes (LSL) — Movement and Expansion

Long-slotted holes provide the most adjustment — approximately 2.5 times the bolt diameter in slot length. They are used when the connection must accommodate significant structural movement.

When to Use Long-Slotted Holes

• Expansion joints — to accommodate thermal expansion and contraction of the structure
• Gravity-only connections — where the connection must allow movement in one direction while transferring gravity loads
• Connections to concrete — to accommodate differential settlement or creep
• Seismic connections — in some special detailing where controlled movement is required

Restrictions

• Restricted to slip-critical connections only (AISC 360 Section J3.2)
• Plate washers or structural washers required — must cover the full length of the slot
• Reduced slip resistance — h_sc = 0.70 (parallel to load) or 0.85 (perpendicular)

Net Area Deduction for Hole Size

Per AISC 360 Section B4.3, the hole deduction for net area calculations adds an extra 1/16" to the actual hole diameter to account for material damage from punching:

Net area hole deduction = actual hole diameter + 1/16"

Examples by Bolt Diameter and Hole Type

Key point: Oversized holes increase the net area deduction by approximately 3/16" per hole compared to standard holes. In tension members with multiple bolt lines, this can significantly reduce the net area and the tension capacity.

Net Area Calculation Example

A 1/2" plate with two lines of 3/4" bolts in standard holes:

Gross width = 8"
Deduction per hole = 13/16 + 1/16 = 7/8"
Two holes across the section: 2 x 7/8 = 1-3/4"
Net width = 8 - 1.75 = 6.25"
Net area = 6.25 x 0.50 = 3.125 in^2

If the same plate uses oversized holes:

Deduction per hole = 15/16 + 1/16 = 1"
Two holes: 2 x 1 = 2"
Net width = 8 - 2.0 = 6.00"
Net area = 6.00 x 0.50 = 3.000 in^2

The oversized holes reduce the net area by 4% (3.000 vs 3.125 in^2).

Slip Resistance Factors by Hole Type

For slip-critical connections, the hole type affects the slip resistance through the factor h_sc:

The slip resistance of one bolt in a slip-critical connection is:

R_n = mu x h_sc x T_b x n_s

Where:

• mu = mean slip coefficient (depends on faying surface preparation)
• h_sc = hole type factor from the table above
• T_b = minimum bolt pretension
• n_s = number of slip planes

Hole Type Selection Guide

Rule of thumb: Use standard holes unless there is a specific, documented reason for a different type. Non-standard holes add cost (wider slots, washers, slip-critical requirements) and reduce capacity.

Calculator

Check bolt connections with any hole type using our free tool:

• Bolted Connections Calculator — Bearing, tearout, slip-critical, and block shear checks for all hole types
• Bolt Hole Sizes Reference — Detailed Table J3.3 with design notes

FAQ

Q: What is the standard hole size for a 3/4" bolt? A: 13/16" (0.8125"). The standard clearance is 1/16" over the bolt diameter. This is the most common question about AISC bolt holes.

Q: Can I use oversized holes in a bearing-type connection? A: No. AISC 360 Section J3.2 restricts oversized holes to slip-critical connections only. In bearing-type connections, the bolt engages bearing against the hole wall, and oversized holes would allow excessive deformation before bearing is engaged.

Q: What is the difference between short-slotted and long-slotted holes? A: Short-slotted holes are approximately d + 1/4" long (one bolt diameter plus 1/4"). Long-slotted holes are approximately 2.5d long (two and a half bolt diameters). Short-slotted holes can be used in bearing-type connections if oriented perpendicular to the load. Long-slotted holes are restricted to slip-critical connections.

Q: How much does the net area deduction increase with oversized holes? A: The deduction increases by 3/16" per hole compared to standard holes (from d + 1/16" to d + 5/16"). For a connection with 4 bolt holes across the section, this reduces the net area by 4 x 3/16 x t = 0.75t square inches.

Q: Do I need washers for oversized holes? A: Yes. When oversized holes appear in an outer ply (the outside plate or angle), AISC 360 requires plate washers to cover the excess hole area and distribute the bolt clamping force. Standard round washers may not be sufficient — the washer must be large enough to fully cover the oversized hole.

Q: Can I mix hole types in the same connection? A: Yes, but each bolt's slip resistance must be calculated using the h_sc factor for its specific hole type. If a connection has standard holes in the web and oversized holes in the flange, the flange bolts will have 85% of the slip resistance of the web bolts.

Related: AISC 360-22 Steel Design Overview | AISC Block Shear — Section J4.3 | AISC Bolt Spacing | AISC Table D3.1 — Shear Lag Factor | Bolt Bearing and Tearout | Bolt Grades