06-22-2012, 05:26 AM
If you were using two 1/2 diameter forged steel eyelets, the yield strength combined for these two eyes is around 25,000 pounds. Now I am not suggesting you can safely lift that much, but I reckon no hobby machinist has a machine that weighs anywhere near that and the point being that one eyelet would safely lift a cross slide table, let alone two and you could always move them closer together so the lift angle was not so acute.
Many years ago I worked in a testing laboratory and did many test on tensile strengths of various materials. Standard off the shelf 1/2" diameter course threaded all thread rod (from back then) would yield at nearly 10,000 pounds. If you use a 75% safety factor, then 1/2" all thread would be adequate for a 2,500 pound tensile load (remember tensile load, not shear load). Interestingly enough, about this time was when some of the early synthetic materials came to the market and I was amazed at how strong some of the tiniest fibers were. The machine I used was able to exert up to 300,000 pounds of force in 1 pound increments. Some of the biggest challenges was to figure out how to fixture the material in order to pull on it!
Many years ago I worked in a testing laboratory and did many test on tensile strengths of various materials. Standard off the shelf 1/2" diameter course threaded all thread rod (from back then) would yield at nearly 10,000 pounds. If you use a 75% safety factor, then 1/2" all thread would be adequate for a 2,500 pound tensile load (remember tensile load, not shear load). Interestingly enough, about this time was when some of the early synthetic materials came to the market and I was amazed at how strong some of the tiniest fibers were. The machine I used was able to exert up to 300,000 pounds of force in 1 pound increments. Some of the biggest challenges was to figure out how to fixture the material in order to pull on it!