Carriage Bolts: Round Head Square Neck
| Carriage Bolts: Round Head, Square Neck (ASME B18.5-1990) | ||||||||||
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Basic Bolt Diameter Click on the size to shop products |
Body Diameter (E) |
Head Diameter (A) | Head Height (H) | Square Width (O) | Square Depth (P) | |||||
| Max | Min | Max | Min | Max | Min | Max | Min | Max | Min | |
| 8 | .1640 | .157 | .328 | .298 | .102 | .083 | .169 | .155 | .108 | .078 |
| 10 | .1900 | .182 | .436 | .436 | .114 | .094 | .199 | .185 | .125 | .094 |
| 12 | .2160 | .206 | .500 | .468 | .149 | .125 | .215 | .197 | .135 | .105 |
| 1/4 | .2500 | .237 | .594 | .563 | .145 | .125 | .260 | .245 | .156 | .125 |
| 5/16 | .3125 | .298 | .719 | .688 | .176 | .156 | .324 | .307 | .187 | .156 |
| 3/8 | .3750 | .360 | .844 | .782 | .208 | .188 | .388 | .368 | .219 | .188 |
| 7/16 | .4375 | .421 | .969 | .907 | .239 | .219 | .452 | .431 | .250 | .219 |
| 1/2 | .5000 | .483 | 1.094 | 1.032 | .270 | .250 | .515 | .492 | .281 | .250 |
| 5/8 | .6250 | .605 | 1.344 | 1.219 | .344 | .313 | .642 | .616 | .344 | .313 |
| 3/4 | .7500 | .729 | 1.594 | 1.469 | .406 | .375 | .768 | .741 | .406 | .375 |
| Carriage Bolts: Round Head, Square Neck: Tolerance on Length | |||||||
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| Nominal Bolt Size |
Nominal Bolt Length | ||||||
| Up to 1" | Over 1" - 2-1/2" | Over 2-1/2" - 4" | Over 4" - 6" | Longer than 6" | |||
| No. 8 - 3/8 | +.02, -.03 | +.02, -.04 | +.04, -.06 | +.06, -.10 | +.10, -.18 | ||
| 7/16 & 1/2 | +.02, -.03 | +.04, -.05 | +.06, -.08 | +.08, -.10 | +.12, -.18 | ||
| 9/16 - 3/4 | +.02, -.03 | +.06, -.08 | +.08, -.10 | +.10, -.10 | +.14, -.18 | ||
- Length of a carriage bolt is measured from the underhead bearing surface to the extreme end of the bolt.
- ASME B18.5-1990 does not specify dimensions for the #8 or #12 diameters. Data listed for these sizes is independent of the ASME specification.
| Low Carbon & Hot Dipped Galvanized Carriage Bolt | |||
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Low Carbon Steel
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Hot Dipped Galvanized Steel
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| Description | Round head bolt with square neck and a unified thread pitch. Made from low or medium carbon steel. | Round head bolt with square neck and a unified thread pitch. Made from low or medium carbon steel with a galvanized zinc finish. | |
| Applications | The square neck is designed to keep the bolt from turning as the nut is tightened. | Often used for outdoor furniture because of the thicker protective coating. | |
| Material |
AISI 1006-1050 or equivalent steel | AISI 1006-1050 or equivalent steel | |
| Core Hardness | Rockwell B70-B100 | Rockwell B70-B100 | |
| Proof Load | 33,000 psi | ||
| Yield Strength | 36,000 psi min. | ||
| Tensile Strength | 60,000 psi min. | ||
| Elongation | 18% min | ||
| Reduction of Area | 35% min | ||
| Minimal Thread Length | The minimum length of thread shall be equal to twice the basic bolt diameter plus .025" for bolts <6", and twice the diameter plus .50" for bolts >6". | ||
| Grades-5 & 8 Carriage Bolts | |||
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| Description | Carriage bolt made from medium carbon steel and heat-treated | Carriage bolt made from medium carbon alloy steel and heat-treated. | |
| Applications | Greater load carrying capacity compared to a low carbon carriage bolt. | Greater load carrying capacity compared to a Grade-5 carriage bolt. | |
| Material |
AISI 1030-1050 or equivalent steel | Medium carbon alloy steel | |
| Heat Treatment | Heat treated, oil or water-quenched, and tempered at min. 800 Degrees (F) | Heat treated, oil-quenched, and tempered at min. 800 Degrees (F) | |
| Core Hardness | 1/4 - 1" Diameter: Rockwell C25-C34 | 1/4 - 1" Diameter: Rockwell C33-C39 | |
| Surface Hardness | 1/4 - 1" Diameter: Rockwell 30N54 max | 1/4 - 1" Diameter: Rockwell 30N 58.6 max | |
| Proof Load | 1/4 - 1" Diameter: 85,000 psi | 1/4 - 1" Diameter: 120,000 psi | |
| Yield Strength | 1/4 - 1" Diameter: 92,000 psi min | 1/4 - 1" Diameter: 130,000 psi min | |
| Tensile Strength | 1/4 - 1" Diameter: 120,000 psi | 1/4 - 1" Diameter: 150,000 psi min | |
| Elongation | 14% Min | 12% Min | |
| Reduction of Area | 35% Min | 35% Min | |
| Minimal Thread Length | The minimum length of thread shall be equal to twice the basic bolt diameter plus .025" for bolts <6", and twice the diameter plus .50" for bolts >6". | ||
| Plating | Typically Zinc Yellow | ||
| Stainless Steel 18-8 Carriage Bolt | ||
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| Description | Round head bolt with a square neck under the head, unified thread pitch, made from austenitic alloy stainless steel. | |
| Applications | Use in environments which require general atmospheric corrosion resistance. | |
| Material |
Made from any of the following: 302, HQ, 303, 303Se, 304, XM7 (Chromium Content 17-19% and Nickel Content 8-10%) | |
| Heat Treatment | The austenitic alloys develop their strength through work hardening during the fastener manufacturing process. The only heat treatment normally available on austenitic stainless alloys is annealing, which is done at approx. 1900 Degrees (F) to a dead soft condition and is not normally thermally reversible. | |
| Hardness | 1/4 - 1/2" Diameter: Rockwell B95-C32 | |
| Yield Strength | 1/4" - 1/2", 2.25 Diameter and Longer: 65,000 psi min | |
| Tensile Strength | 1/4 - 1/2" Diameter, 2.25 Diameter and longer: 100,000-150,000 psi min | |
| Elongation in 4D | 1/4" - 1/2" Diameter: 20% min | |
| Minimal Thread Length | The minimum length of thread shall be equal to twice the basic bolt diameter plus .025" for bolts <6". | |
Carriage Bolts: Round Head Short Neck
| Carriage Bolts: Round Head, Short Neck (ANSI/ASME B18.5) | |||||||||||||
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Nominal Size or Basic Bolt Diameter Click on the size to shop products |
Body Diameter (B) |
Head Diameter (W) | Head Height (H) | Square Width (S) | Square Depth (N) | Corner Radius on Square (C) | Fillet Radius (R) | ||||||
| Max | Min | Max | Min | Max | Min | Max | Min | Max | Min | Max | Max | ||
| 1/4 | .2500 | .260 | .213 | .594 | .563 | .145 | .125 | .260 | .245 | .124 | .093 | .031 | .031 |
| 5/16 | .3125 | .324 | .272 | .719 | .688 | .176 | .156 | .324 | .307 | .124 | .093 | .031 | .031 |
| 3/8 | .3750 | .388 | .329 | .844 | .782 | .208 | .188 | .388 | .368 | .156 | .125 | .047 | .031 |
| 7/16 | .4375 | .452 | .385 | .969 | .907 | .239 | .219 | .452 | .431 | .156 | .125 | .047 | .031 |
| 1/2 | .5000 | .515 | .444 | 1.094 | 1.032 | .270 | .250 | .515 | .492 | .156 | .125 | .047 | .031 |
| 5/8 | .6250 | .642 | .559 | 1.344 | 1.219 | .344 | .313 | .642 | .616 | .218 | .187 | .078 | .062 |
| 3/4 | .7500 | .768 | .678 | 1.594 | 1.469 | .406 | .375 | .768 | .741 | .218 | .187 | .078 | .062 |
| Carriage Bolts: Round Head, Short Neck: Tolerance on Length | |||||||
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| Nominal Bolt Size |
Nominal Bolt Length | ||||||
| Up to 1" | Over 1" - 2-1/2" | Over 2-1/2" - 4" | Over 4" - 6" | Longer than 6" | |||
| No. 10 - 3/8 | +.02, -.03 | +.02, -.04 | +.04, -.06 | +.06, -.10 | +.10, -.18 | ||
| 7/16 & 1/2 | +.02, -.03 | +.04, -.05 | +.06, -.08 | +.08, -.10 | +.12, -.18 | ||
| 9/16 - 3/4 | +.02, -.03 | +.06, -.08 | +.08, -.10 | +.10, -.10 | +.14, -.18 | ||
| 7/8 & 1 | +.08, -.10 | +.10, -.14 | +.12, -.16 | +.16, -.20 | |||
| 1-1/8 - 1-1/2 | +.12, -.12 | +.16, -.16 | +.18, -.18 | +.22, -.22 | |||
- Length of a carriage bolt is measured from the underhead bearing surface to the extreme end of the bolt.
| Carriage Bolt: Round Head, Short Neck Properties | ||
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| Description | A round head bolt with a short, square shoulder under the head, and a unified thread pitch. The bolt is made from low or medium carbon steel | |
| Applications | Designed to keep the bolt from turning when a nut is being tightened. The short neck is used with sheet metal where a standard size neck would create an obstruction. | |
| Material |
AISI 1006-1050 or equivalent steel | |
| Hardness | Rockwell B70-B100 | |
| Proof Load | 33,000 psi | |
| Tensile Strength | 60,000 psi min. | |
| Yield Strength | 36,000 psi min. | |
| Elongation | 18% min | |
| Reduction of Area | 35% min | |
| Minimal Thread Length | The minimum length of thread shall be equal to twice the basic bolt diameter plus .025" for bolts <6", and twice the diameter plus .50" for bolts >6". | |
Carriage Bolts: Round Head, Ribbed Neck
| Carriage Bolts: Round Head, Ribbed Neck (ASME B18.5-1998) | |||||||||||||||
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Nominal Size or Basic Bolt Diameter Click on the size to shop products |
Body Diameter (B) |
Head Diameter (W) | Head Height (H) | Head to Ribs (M) | Number of Ribs | Diameter Over Ribs (V) | Depth Over Ribs (D) | Fillet Radius (R) | |||||||
| Max | Min | Max | Min | Max | Min | Up to 7/8" Length | 1"+ Length | Approx. | Min | Up to 7/8" Length | 1" & 1-1/8" Length | 1-1/4"+ Length | Max | ||
| No 10 | .1900 | .199 | .182 | .469 | .438 | .114 | .094 | .031 | .063 | 9 | .210 | .250 | .407 | .594 | .031 |
| 1/4 | .2500 | .260 | .237 | .594 | .563 | .145 | .125 | .031 | .063 | 10 | .274 | .250 | .407 | .594 | .031 |
| 5/16 | .3125 | .324 | .298 | .719 | .688 | .176 | .156 | .031 | .063 | 12 | .340 | .250 | .407 | .594 | .031 |
| 3/8 | .3750 | .388 | .360 | .844 | .782 | .208 | .188 | .031 | .063 | 12 | .405 | .250 | .407 | .594 | .031 |
| 7/16 | .4375 | .425 | .421 | .969 | .907 | .239 | .219 | .031 | .063 | 14 | .470 | .250 | .407 | .594 | .031 |
| 1/2 | .5000 | .515 | .483 | 1.094 | 1.032 | .270 | .250 | .031 | .063 | 16 | .534 | .250 | .407 | .594 | .031 |
| 5/8 | .6250 | .642 | .605 | 1.344 | 1.219 | .344 | .313 | .094 | .094 | 19 | .660 | .313 | .438 | .625 | .062 |
| 3/4 | .7500 | .768 | .729 | 1.594 | 1.469 | .406 | .375 | .094 | .094 | 22 | .785 | .313 | .438 | .625 | .062 |
| Carriage Bolts: Round Head, Ribbed Neck: Tolerance on Length | |||||||
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| Nominal Bolt Size |
Nominal Bolt Length | ||||||
| Up to 1" | Over 1" - 2-1/2" | Over 2-1/2" - 4" | Over 4" - 6" | Longer than 6" | |||
| No. 10 - 3/8 | +.02, -.03 | +.02, -.04 | +.04, -.06 | +.06, -.10 | +.10, -.18 | ||
| 7/16 & 1/2 | +.02, -.03 | +.04, -.05 | +.06, -.08 | +.08, -.10 | +.12, -.18 | ||
| 9/16 - 3/4 | +.02, -.03 | +.06, -.08 | +.08, -.10 | +.10, -.10 | +.14, -.18 | ||
| 7/8 & 1 | +.08, -.10 | +.10, -.14 | +.12, -.16 | +.16, -.20 | |||
| 1-1/8 - 1-1/2 | +.12, -.12 | +.16, -.16 | +.18, -.18 | +.22, -.22 | |||
- Length of a carriage bolt is measured from the underhead bearing surface to the extreme end of the bolt.
-Tolerance on #10 through 1/2" sizes for nominal lengths of 7/8" and shorter shall be +.031 and -.000
| Carriage Bolt: Round Head, Ribbed Neck Properties | ||
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| Description | A round head bolt with a ribbed or serrated shoulder made from low carbon steel. | |
| Applications | For use in soft, ductile metals, wood and plastics to keep the bolt from turning when the nut is being tightened. | |
| Material |
Carbon Steel - Carbon: .55% max, Phosphorus: .048% max, Sulfur: .058% max | |
| Hardness | Rockwell B70-B100 | |
| Tensile Strength | 60,000 psi min. | |
| Yield Strength | 36,000 psi min. | |
| Elongation | 18% min | |
| Reduction of Area | 35% min | |
Carriage Bolts: Fin Neck
| Carriage Bolts: Fin Neck (ASME B18.5-1990) | |||||||||||||||
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Nominal Size or Basic Bolt Diameter |
Body Diameter (D) |
Head Diameter (W) | Head Height (H) | Fin Thickness (T) | Distance Across Fins (A) |
Fin Depth (F) | Fillet Radius (R) | ||||||||
| Max | Min | Max | Min | Max | Min | Max | Min | Max | Min | Max | Min | Max | Min | ||
| No 10 | .1900 | .199 | .182 | .469 | .438 | .114 | .094 | .098 | .078 | .395 | .375 | .088 | .076 | .031 | .015 |
| 1/4 | .2500 | .260 | .237 | .594 | .563 | .145 | .125 | .114 | .094 | .458 | .438 | .104 | .094 | .031 | .015 |
| 5/16 | .3125 | .324 | .298 | .719 | .688 | .176 | .156 | .145 | .125 | .551 | .531 | .135 | .125 | .031 | .015 |
| 3/8 | .3750 | .388 | .360 | .844 | .782 | .208 | .188 | .161 | .141 | .645 | .625 | .151 | .141 | .031 | .015 |
| 7/16 | .4375 | .452 | .421 | .969 | .907 | .239 | .219 | .192 | .172 | .739 | .719 | .182 | .172 | .031 | .015 |
| 1/2 | .5000 | .515 | .483 | 1.094 | 1.032 | .270 | .250 | .208 | .188 | .833 | .813 | .198 | .188 | .031 | .015 |
| Carriage Bolts: Fin Neck: Tolerance on Length | |||||||
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| Nominal Bolt Size |
Nominal Bolt Length | ||||||
| Up to 1" | Over 1" - 2-1/2" | Over 2-1/2" - 4" | Over 4" - 6" | Longer than 6" | |||
| No. 10 - 3/8 | +.02, -.03 | +.02, -.04 | +.04, -.06 | +.06, -.10 | +.10, -.18 | ||
| 7/16 & 1/2 | +.02, -.03 | +.04, -.05 | +.06, -.08 | +.08, -.10 | +.12, -.18 | ||
| Carriage Bolt: Fin Neck Properties | ||
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| Description | A round head bolt with a flat bearing surface which intersects with the shank at a 90 degree angle. Where the bearing surface and shank meet are two fins, 180 degrees opposite each other. The bolt is made from low carbon steel. | |
| Applications | For use in thin plywood to keep the bolt from turning when nut is being tightened. | |
| Material |
Carbon Steel - Carbon: .55% max, Phosphorus: .060% max, Sulfur: .150% max | |
| Hardness | Rockwell B69-B100 | |
| Tensile Strength | 60,000 psi min. | |
| Yield Strength | 36,000 psi min. | |
| Elongation | 18% min | |
| Reduction of Area | 35% min | |
Carriage Bolts: Flat Head, Square Neck
| Carriage Bolts: Flat Head, Square Neck | ||||||||
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Bolt Diameter & Thread Pitch Click on the size to shop products |
Head Diameter (A) |
Head Height (T) | Square Width (O) | Square Depth (D) | ||||
| Max | Min | Max | Min | Max | Min | Max | Min | |
| 1/4-20 | .640 | .590 | .098 | .078 | .260 | .245 | .156 | .125 |
| Carriage Bolts: Flat Head, Square Neck: Tolerance on Length | ||
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| Nominal Bolt Size |
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| No. 10 - 3/8 | +.02, -.04 | |
| Carriage Bolt: Flat Head, Square Neck | ||
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| Description | A flat head bolt with a bearing surface that is countersunk to a 150 degree angle. Although flat, the head has a measurable side height causing it to protrude above its mating surface when it is completely tightened. Directly below the head is a square neck and a threaded section that has a unified thread pitch. | |
| Applications | The square neck design keeps the bolt from turning as a nut is tightened. The flat head feature gives a lower profile on the front or top side of the fastening than a round head carriage bolt. Designed specifically, but not exclusively for the garage door industry. | |
| Material |
Grade-2: AISI 1006-1025 Steel; Grade-5: AISI 1030-1055 Steel |
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| Core Hardness | Grade-2: Rockwell B80-B100; Grade-5: Rockwell C25-C34 | |
| Tensile Strength | Grade-2: 74,000 psi. min.; Grade-5: 120,000 psi. min. | |
| Plating | Flat head carriage bolts are usually supplied with a clear zinc finish | |
Additional Resources
