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A307 Flat Head Carriage Bolt

Flat Head Carriage Bolt
Flat Head Carriage bolts may be available in other diameters however the only standard diameter is in the 1/4" with the pictch of 1/4-20. These have a bearing surface that is countersunk to a 150 degree angle. This bolt has  a protruding square under the head for locking the bolt into a mating square
hole. These are used mostly in the garage door industry. See below for the lengths they are available in.

Flat Head Carriage Bolt
Bolt Diameter and Thread Head Diameter Head
  A T O D
Max Min Max Min Max Min Max Min
1/4-20 .640 .590 .098 .078 .260 .245 .155 .125
Tolerance on Length: +0.02, -0.04
A307 Steel With Zinc Finish

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