I'm building a small rolling gantry with telescoping legs. Each leg should be able to hold 1 ton of weight. The legs are made of 3/16" wall structural steel square tubing, which is A500 steel, which withstands a minimum of 39,000 psi at yield point according to my steel handbook.

I figure the pin will only push on half of the hole. The surface area of half of a hole = PI***DIA***3/32.

What I'm not sure of is how to actually design the pin & hole. Can I just multiply my half hole area times 39,000 to get a raw number, which I then derate until I'm comfortable? Or am I looking at this wrong?

To use an example, if I use a 5/8" pin in a 5/8" hole, the pin presses down on half of the hole's area. That surface area I get as .184 sq. inches, and multiplying that times 39k gives me about 7179 pounds, or about 3½ tons.

If I use a 3/4" pin/hole, I get 8614 pounds - more surface area.

Going up to a 1" pin, I calculate 11486 pounds.

Am I doing this right? How big a derating factor would ***you*** be comfortable with?

Grant