Bolt Edge Distances – Minimum Spacing, Pitch and Design Guidance

Standard edge distances and bolt spacing are defined in BS 5950 and Eurocode (BS EN 1993), with larger distances recommended for full strength and fatigue conditions. This page provides a bolt edge distance chart, pitch spacing values and practical design guidance for structural and mechanical applications.

Edge Distances

Minimum Edge Distances as identified in BS 5950-1 2000 "Structural use of steelwork in building. Code of practice for design. Rolled and welded sections".

Notes;
BS EN 1993-3 2005 supersedes this standard and the edge distances in this standard seem to be a bit less than the ones I have listed. However I have maintained my figures in line with the original version.

It must be stated that connections under tension with the end edge distance (b = 1,4 D) cannot withstand the full load that is possible with the bolted connection. An end distance of B = 2D is required to achieve this maximum strength. See bolt spacing and pitch tables.

How to Use These Edge Distances

Bolt edge distances are critical in preventing tearing, shear failure and bearing failure of the plate material. The values in the table represent minimum distances for safe design, but in practice larger distances are often used.

• Use minimum values only where space is restricted
• Increase edge distance for dynamic or fatigue loading
• Ensure adequate spacing to avoid plate tearing under tension
• Consider fabrication tolerances when setting minimum distances

Bolt Size (Nominal Diameter d)	Clearance Hole (D)	Pitch (A)	Min Edge(B)	Min Edge(C)
M12	14	30	20	18
M16	18	40	26	23
M20	22	50	31	28
M24	26	60	37	33
M27	30	68	42	38
M30	33	75	47	42
M36	39	90	55	49

Design Guidance

Minimum edge distances are based on preventing local failure at the plate edge. However, good engineering practice is to exceed these values where possible.

• For maximum strength: Use edge distances ≥ 2D
• For structural connections: Follow Eurocode (BS EN 1993)
• For fatigue conditions: Increase spacing significantly
• Avoid: placing bolts too close to edges in tension zones

Common Design Mistakes

• Using minimum edge distance for all designs
• Ignoring direction of load when placing bolts
• Not allowing for hole clearance and tolerances
• Assuming tabulated values apply to all materials

Basic Design Check

Minimum edge distance is often expressed as a multiple of bolt diameter:

Edge Distance ≥ 1.5D to 2D

Frequently Asked Questions

What is minimum edge distance for bolts?

Minimum edge distance is the distance from the centre of a bolt hole to the edge of the plate, typically between 1.5D and 2D depending on the application and standard used.

Why is edge distance important?

Edge distance is important to prevent tearing, shear failure and bearing failure at the plate edge in bolted connections.

What edge distance is required for full strength?

An edge distance of at least 2D is generally required to achieve full strength in structural connections.

Which standards define bolt edge distances?

Bolt edge distances are defined in standards such as BS 5950 and Eurocode (BS EN 1993), depending on the design requirements.

Relevant links

1. Edge distances -American(inch sizes).. The american standards , as shown seem to go towards 1,5.D
2. exelcalcs .. Edge spacing Calculations based on Excel