Drilling/welding Pre-cautions

What is the diameter of the hole? Is it closer to the end of the flange or toward the radius?

Pic?

Also where on the truck. Top, bottom, front, rear…..

 

Top flange I really wouldn't worry. Top flange is compressing not pulling. Bottom flange I wouldn't like at all.
I don't like to admit this but probably 15 years ago I drilled 4 holes in my top flange between cab and fifth wheel. Ran that way for a few years then I put a bolt in the hole cut off the head and welded it in. Ground it smooth and you'd never know it's there. Still running truck today

 

At one time KW used to drill the lower flange to mount the rear spring hangers on the steer axle. Manufacturers are smarter than us (sometimes).

 

International had issues with top flanges cracking on school bus’s right in front of the LF cab mount.

Their fix was to drill stop the crack , V it out and MiG weld it. Never an issue.

I would weld the hole in and keep an eye on it.

Good lesson for your apprentice, I bet. Don’t beat him too hard.

 

I'm no frame shop. I'm a shadetree fabricator. So my opinion is worth the full price you're paying for it.

This rule applies to the web as well as the flanges, compression and tension. Use a reamer to get an exact fit to the bolt of choice. Preferably a bolt with a short shank at the head. Tighten the bolt to spec.

As the frame rail flexes an unfilled hole or one with a loose fit filler, will elongate and misshape. As it does this over and over 10s of thousands of times, the metal surrounding the hole will "work harden" and/or "cycle fatigue" and become brittle. Cracks will follow and eventual failure will happen.
If you fill the hole with a fastener tight enough that does not allow the hole to misshape or elongate etc. It can not cycle.

That rule was passed down to my from highly experienced old fabricators that also dabbled in blacksmithing. So.....for what's it's worth, that's my opinion.

 

You'll be okay, just ream for a tight fitting bolt.
Here is the Peterbilt I am working on this morning. First picture is within 12" of other two pics...