Fastener Torque resource for thin material

I’ve got a 1/4-20 fastener into a .188 thick wall in square tubing.

I normally like to run with thread depth = diameter x 1 but in this case, there’s nothing much I can do. I have 6 fasteners total holding on a stout trailer fender on an equipment trailer I’m designing.

Were I tightening the bolts, I would not worry about it much, but I’m afraid without a torque spec the production guys will be stripping these out occasionally.

Can someone refer me to a torque chart that takes material thickness into consideration? OR help me figure this out? OR give me your best guess based on experience?

Was thinking about having the machinist make me a sample I could use to find “yield torque” where the fastener strips out the wall, then back it up 10% or something.



Watch the video. Here is a screen grab…

Above is a snippet.