Structural Bolts vs. Grade 5 Bolts
Structural Bolts vs. Grade 5 Bolts
(OP)
Can anyone tell me the difference between a Structural Bolt and a Grade 5 bolt of the same size?
I am a Mechanical Engineer working for a company that manufactures heavy duty, industrial shelving…all bolted together.
These shelving units are required to hold very large loads placed upon them (2-5 tons).
The bolts in question are used to fasten the base to an upright verticle column, creating esensially an inverted "T". The head and nut distance across the flats, for the Structural Bolt is 1.25", whereas the distance across the flats on a grade #5 bolt and nut is 1.125".
So...the question is:
Is there sufficient surface contact under the head of the nut and bolt (grade 5) to create the suffient "friction fitting", between the two members (base & verticle upright), so they can't "shift"?
Any idea how one would calculate the force (torque) needed to achieve this?
I could only imagine that it would have to do with the total surface area of the two plates (and surface condition/finish) vs. the surface area of the head of the nut/bolt and its compressional strength, and of course, how many were being used. In this case, the two plates are 8" x 16" (128 in/sq surface area). They are fastened together using (4) 3/4" dia. bolts. The material is just CRS, powder coated.
I’ve noticed recently that when these units were originally designed, they were designed using “Structural Bolts” and at some point over the years they were changed to Grade 5 Bolts.
I am concerned as to whether or not the structural integrity of the unit has been compromised.
Can you help?
I am a Mechanical Engineer working for a company that manufactures heavy duty, industrial shelving…all bolted together.
These shelving units are required to hold very large loads placed upon them (2-5 tons).
The bolts in question are used to fasten the base to an upright verticle column, creating esensially an inverted "T". The head and nut distance across the flats, for the Structural Bolt is 1.25", whereas the distance across the flats on a grade #5 bolt and nut is 1.125".
So...the question is:
Is there sufficient surface contact under the head of the nut and bolt (grade 5) to create the suffient "friction fitting", between the two members (base & verticle upright), so they can't "shift"?
Any idea how one would calculate the force (torque) needed to achieve this?
I could only imagine that it would have to do with the total surface area of the two plates (and surface condition/finish) vs. the surface area of the head of the nut/bolt and its compressional strength, and of course, how many were being used. In this case, the two plates are 8" x 16" (128 in/sq surface area). They are fastened together using (4) 3/4" dia. bolts. The material is just CRS, powder coated.
I’ve noticed recently that when these units were originally designed, they were designed using “Structural Bolts” and at some point over the years they were changed to Grade 5 Bolts.
I am concerned as to whether or not the structural integrity of the unit has been compromised.
Can you help?





RE: Structural Bolts vs. Grade 5 Bolts
RE: Structural Bolts vs. Grade 5 Bolts
That is EXACTLY what I was looking for!
I have spent 10 years in Automation and know I can't remember how to work this stuff anymore...thanks for your help.
Is there a specific formula or table that you used to come to this?
RE: Structural Bolts vs. Grade 5 Bolts
I got this from my wrinkled, dog eared, yellowed, faded, coffee stained page that was Xeroxed from somewhere long since forgotten!
I just Googled this page which, oddly enough, has the same values I quoted!
http://www.team.net/sol/tech/torque.html
RE: Structural Bolts vs. Grade 5 Bolts
I'm new to this forum. I hope that I can be of assistance to someone in the future!
Thanks again!
RE: Structural Bolts vs. Grade 5 Bolts
RE: Structural Bolts vs. Grade 5 Bolts
I have, however, been finding quite a bit off information over the last few days and , apparently, there's not a whole lot of difference between a Structural (A325) Bolt and a Grade 5 Bolt. Both, basically, have the same qualities, with exception to the head and nut size.
And, yes, you are correct...a Grade 8 blows them both away!
Thanks again,
cadman5150
RE: Structural Bolts vs. Grade 5 Bolts
A325 is different than grade 5 in these ways:
- Better quality control (since they hold buildings together).
- Heavy hex head instead of standard (as you found)
- Less thread length so you can use more of the shank for shear.
A few caveats on the above discussion...
Grade 8: the #s look good but if they are plated they can be prone to hydogen embrittlement. Also, the lower quality control (esp. in import fasteners) can mean lack of ductility, plated or not.
Torque: unfortunately not very reliable as a measure of actual bolt tension. If tension is critical you can use a load indicating washer, or appropriate Belleville.
A great summary of bolt info is at
http://www.fastenal.com/web/documents/FastenalTechnicalReferenceGuide.pdf
(esp. p. 16-24)
RE: Structural Bolts vs. Grade 5 Bolts
An EXCELLENT source!
RE: Structural Bolts vs. Grade 5 Bolts
Rod
RE: Structural Bolts vs. Grade 5 Bolts
Rod