1 inch Machine A307 Bolts Torque Value 1

[cap4000]

Does anyone know a typical torque value for an ungraded ordinary machine ASTM A307 Grades A or B one inch diameter bolt. Grade C is of A36 typical steel values. The problem is that their is no Fy yield stress given in the ASTM standards for A or B bolts and thus their is no proof load associated with either A or B bolts. Any practical field experience feedback on this one would be greatly appreciated.

 

[Redfish205]

Have you tried Manual of Steel conctruction, ASD 9th Edition, Part 4 or Manual of Steel Constr. LRFD 3Rd Edition
Part 7?

 

[RARWOOD]

In heavy timber construction A307 bolts are commonly used for wood to wood, and wood to steel connections ( personally I would not use ASTM A325 or A490 bolts in wood construction). I have been asked a lot about what torque value should be used to install the A307 bolts. I tell people they should be snug tight.

To me snug tight is just past finger tight, tight enough that you need a wrench to loosen the bolt. In a wood to wood connection the bolt should not be tighten to the point that the washer is embeding into the wood.

With wood the bolt values are established so that they apply to bolts that are tight and to bolts which have lossened due to wood shrinkage.

 

[boo1]

The ASTM A307 bolts (ASTM designation A307-83a) have a specified minimum tensile strength of 60 ksi. In application, A307 bolts and nuts are tightened so that some axial force is present that will prevent movement of the connected members in the axial direction of the bolt. Proper tightening also prevents loosening of the nut. The actual force in the bolt is not closely controlled and may vary substantially from bolt to bolt. Because of the small axial forces, little frictional resistance is developed, and in most situations the bolt will slip into bearing. This results in shear stresses in the bolts and contact stresses at the points of bearing.

 

[mrMikee]

Start with this thread thread404-143701 which contains links to other threads. I think there was some good info provided.

-Mike

 

[RARWOOD]

boo1

Excellent information!!!

Unfortunately I have seen at least one wood design where the engineer used A307 fasteners and was relying on the clamping force developed in a wood to wood joint to produce friction resistance to prevent slip.

The problem with using friction in a wood to wood joint is that as the wood members dry out and shrink they reduce the clamping force.

 

[boo1]

Agree with RARSWC on wood joints, watch timbers they are the worst for shrinkage. For transmision tower friction joints, I have seen spike plate used.