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1/4 carriage bolt envelope (ASME B18.5 round head, square neck)

1/4 carriage bolt envelope (ASME B18.5 round head, square neck): spherical-cap head Ø15.09 × 3.68 mm (A max, H max), square neck 6.60 mm wide × 3.96 mm deep (O max, P max), plain shank Ø6.35 mm (nominal) × 76.2 mm (3 in, Xem's example length) under the head; no thread, chamfer, corner radius or point

Exact dimensions. True size, no tolerance added. Threads are plain cylinders at the major diameter.

STEP STL free, CC BY 4.0 (credit "Xem Studio")

Dimensions

size (in)1/4
body E max / min.260 / .237
head dia A max / min.594 / .563
head height H max / min.145 / .125
square width O max / min.260 / .245
square depth P max / min.156 / .125
corner radius on square max.031
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From the full sheet

Carriage bolts, ASME B18.5 round head square neck, #10 to 1 in: head, square neck, body diameter + envelope models: every size, notes, mating features and sources. What are the head diameter and square neck size of a 3/8 carriage bolt, and what hole does the square need?

Other sizes