Re: Recoil lug
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: USMC7980</div><div class="ubbcode-body">Keep in mind that the thickness is not what gives the strenght but rather the hardness. I would take a factory thickness properly hardened lug over a .250 or larger un-hardened any day of the week. Now a thick hardened one is the cat's meow (Sounds like a porn line) </div></div>
You have that backwards.
Modulus of Elasticity gives it the deflection "strength" that you're talking about. You want a STIFF lug, not a HARD lug. The E of the material does not change with the heat treat. Non-treated mild 1060 is within 5% of the stiffness of AISI 4340 300M.
You're looking for bending and shear stiffness, not allowable stress level, the thicker one gives you a stiffer lug because of how the moment of inertia works. Given equivalent I's there's virtually no difference between 1060 and 4340 stiffness.
A 3/16" thick vs. 1/4" thick lug gives a 237% increase in I and therefore 237% increase in stiffness.
If you want to talk about total lug package being improved you need a hard lug in the area that it slips over the tenon threads for bearing stress resistance. If you REALLY want the "cat's meow" for a lug, use something like 86xx bearing steel, carburize the 86xx with a thick case so that you have the surface hardness to counteract the bearing stresses and the ductile core with extra thickness so that it's not going to crack from carbon embrittlement.