Minimum Material Thickness for a Tapped Hole. 2

[dik]

I have a 3/8"-24 dia A307 Grade B fastener going into an HSS 6x6x0.188 column. The client wants to drill and tap the column (doesn't want to use TEKS fasteners which I spec'd). The load is less than 15% of the A307 fastener. Min ISO engagement is 5/16"

Is there a minimum wall thickness that I can use? Is calculating the capacity with a good comfy factor adequate? and ignore the engagement length? I don't have a problem doing this unless there is a real contraindication... and just glue it in place with Loktite Red...

Thanks, Dik

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So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

From a website...

https://engineerdog.com/2015/01/11/10-tricks-engineers-need-to-know-about-fasteners/

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So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Stress_Eng]

It is surprising just how many variables go in to influencing the load distribution. The 16 threads distribution shown in the attachment was the result of the displacement compatibility method. For means of comparison, a joint given in a published FE analysis book, using orthotropic properties, was used. There was good agreement between results.

 

[dik]

Thanks... I figured that at half the engagement the capacity would be at least half the capacity and I guessed a max load of about half of that. The load was much smaller than that load, so I was comfortable. My concerns were for loosening because of the light load and I didn't want to overtorque, and strip the threads, so used Loctite Red... I'm happy with my design, and picked up a lot more information, which I like... I'm sort of an info packrat... I even found a copy of Sopwith, which I'll go over later...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[TLHS]

I've done this once or twice for really small stability loads on thick floor plate in retrofit situations where welding isn't appropriate and there's no access below. I did a deep dive in the research and did some fiddly math, but I think the check that made me feel comfortable after doing the theoretical stuff was making sure I had some minimum number of threads pus a sanity check based on the following logic:

- A nut will develop the full capacity of the bolt
- My material is less strong than the material in the nut
- My material is thinner than a nut

Ballpark Capacity = Bolt Capacity * (Material Threaded Height / Nut Threaded Height) * (Material Strength / Nut Material Strength)

 

[dik]

Thanks...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik