All Eagle H-beam rods are forged from certified 4340 chromoly steel. While a lot of companies make rods from this material, if you pay close attention, you will notice not all 4340 is the same. For instance, to be classified as "4340 steel" certain alloying elements must be present in certain percentages. AISI/SAE specifications call for 1.65% to 2.00% nickel content. While this seems like a small difference, understand that this is almost an 18% variation. 4340 steel with 1.65% nickel will act a little differently than 4340 steel with 2.00% nickel content. This is just one of many alloying elements involved in creating 4340 steel. Through extensive material testing, Eagle works closely with the foundry we use to achieve a much tighter tolerance of all alloying elements to our specific requirements. Along with this, the heat treatment and tempering process used is vital to producing a strong steel. While exactly what we do is a closely guarded secret, all of this attention to detail results in a stronger and much more consistent material. Our "4340" steel routinely tests 10-15% stronger than "typical" SAE/AISI spec 4340 steel.
Another important design feature is all Eagle H-beam rods are manufactured from a 2 piece forging. This is significant because it enhances the strength of the rod cap by orienting the "grain" of the metal with the direction of stress. The stress exerted on the cap is perpendicular to the stress on the beam. Forged metal, like wood, has a grain "flow".

While wood is stronger in compression and tension when the stress is applied along the grain, it is weaker when the stress is applied perpendicular to the grain. The same is true for steel. Although not as severely different as wood, forged steel will show the same type of result. It might be minor, but several "minor" enhancements combined together result in a major improvement. Eagle also never uses "cracked cap" type of manufacturing. This is a cheap alternative to try and produce a more perfect fit between the cap and the beam. The problem is that in order for this to work, the rod material must be brittle (that's bad), and we would have to make the rod as a single forging (see above). Instead of resorting to those kind of measures to achieve a "pefect" fit - we just machine the rod and cap perfectly. So much so that it is difficult to see the parting line at all!