Machining A Bolt Head

[bball101453]

I am in a situation where we need to machine down the head of a 3/4" A325 bolt from 1/2" to roughly 3/8" in order to attach a pipe clamp to a steel tube. I was wondering if anyone has done this before and if so how do you determine the new capacity of the bolt. There is not a lot of load on the bolt, should be less than 2 kips, but I was looking for a way to have accurate calculations. Any help would be great. Thanks.

 

[connectegr]

ASME B18.2.6 allows for a minimum head thickness of .455 for a 3/4 ASTM A325 or A490.

Since the design of the bolts shear/tensile strength is primarily based on the cross-sectional area of the bolt. I don't think you can calculate a change in the shear/tensile strength based on the head thickness.

Is there a washer under the bolt head? For standard or OVS holes, a washer is only needed under the turned side. Removing the washer may provide the clearance you seek.

Is the bolt snug-tight or pre-tensioned?

http://www.FerrellEngineering.com

 

[hydtools]

You will have 100 * .378/.5 = 75% of the head shear area.

The shank tensile area is .442 in.^2
The .5 in. head shear area is 7.4 in.^2
The .375 in. head shear area is 5.6 in.^2

Min tensile strength 120ksi. Min shear strength 60ksi. Shear capacity of .375 head is still greater than shank tensile capacity.

Ted

 

[hydtools]

Before I get jumped on too hard, I see my area calcs are incorrect.
The .5 in. head shear area is 1.18 in.^2
The .375 in. head shear area is .88 in.^2
The reduced head shear capacity is about equal to the shank tensile capacity.

Sorry.

Ted

 

[CoryPad]

Head shear capacity is based on the hole size. You can estimate the shear area with pi * hole size * head height.

 

[CoryPad]

My previous reply was cut short. I wanted to say that heads usually are deformation limited and this type of behavior usually is tested.