Which is stronger?

[doctordick]

So if I needed to bolt a piece of 1/4 steel to a piece of 1/2 steel, which will give me max strength: drill and tap the 1/2 and bolt thru the 1/4 OR drill both pieces thru and use nuts. Needs to be removable so don't want to weld. Drill and tap would look cleaner but I want to use the strongest method. (multiple 5/16 bolts)

 

[Elliott]

Drill and tap the half so you don't have to worry about a nut.should be stronger than you would think

 

[jkh533]

Well since a 5/16" nut only has 5/16" of threads I would think the tapped 1/2" would be the better choice

 

[ptweld]

What sre you using it for? Depending on that you could gust weld a nut on the back or go with a higher KSI grade plate to help save on weight.

 

[onetoncrawler]

1/2" material meets the general rule of thumb for bolt strength . simple formula to use 1.5 x diameter of bolt = minimum tap depth

depending on the grade of your bolt the only thing you would be gaining using a nut and flat washer is surface area - this only applies if your bolt is in full tension

if you are putting a shear load on the bolt you will cut the bolt strength in 1/2

 

[doctordick]

Thanks for all the good info, y'all. I'm sure I've overthought this whole thing but the old oil patch habits die hard. "Build it twice as strong as it needs to be and then build it stronger." I think what I've decided on is machining the 1/2 material so that part of the 1/4 material is actually recessed into the other piece with a slight interferance fit. That should reduce both shear and tensile loading on the bolts in this application. My concern with drilling and tapping is thread strength in the mild steel 1/2 material but with a good mechanical fit I'm sure it'll be okay. Maybe all this discussion will help out someone else, too.