Flat Washers for Oversize Holes

[michigander]

When drilling a custom blind flange (ASME App 2), the bolt circle ovalled, and the client would like to use a smaller bolt to compensate. 5/8" bolts would be substituted for the 3/4" bolts. There is sufficient area in the bolts to seat the gaskets. Are there any rules, requirements, or good engineering practices for flat washer use in this type of application in spanning an oversized hole?

 

[JStephen]

As a guide, you might check the AISC specifications for bolting- it is not uncommon to use oversize holes there. I don't know that they give a design method for the washers, but I think they do at least specify acceptable washers for the bolts in question.

If the washers are really required by the design, I would be a bit concerned about the question of whether they get reinstalled each time the thing is reassembled.

 

[mizzoueng]

I cannot think of the code for this, but I would call the machine shop and let someone know that I am very unhappy. Then I would call and order some 5/8" extra wide B7 or greater flat washers for both sides. ASTM A183 is what we are using currently on my project.

 

[michigander]

Thanks so much for all the feedback. I didnt think there was any specific requirements within ASME...but ya never know!

Thanks again...

 

[chicopee]

Yeah but AISC bolt holes are oversized only by 1/16" in dia. and AISC is not dealing with pressurized parts.