What axle material do you use? What makes your axles stronger than stock? Why induction hardening vs thru hardening? Why are your axles machined after heat treating? These are just a few of the questions we address every day at Dutchman.
Induction hardening is the process by which an axle shaft is passed thru an electrical coil, which heats the steel red hot and then quenches the steel to make it hard. The amount of heat put into the steel determines the case depth-the hotter and slower the scan, the deeper and harder the case hardening. The deeper the case, the stronger the shaft. Most stock (oem) shafts made from 1039 steel have a case depth of .125 - .150, and have a hardness of 50-54 on the Rockwell "C" scale. The Dutchman 1541-H shafts have a case depth around the .300 mark and a hardness of 56-59 Rockwell "C" scale. This combo is what gives a 25-30% strength increase over stock 1039 shafts-if you are comparing shafts with a similar length and spline count. Thru hardening is a process by which an axle shaft is heated in a furnace resulting in a shaft that has the same heat treat from the center to the outside diameter. Thru hardened axles have a hardness of 46-48 on the Rockwell "C" scale. The hard case/soft core of an induction hardened 1541-H shaft yields its torsional strength & ductility and the softer "thru Hardening" of a 4340 shaft yields its torsional strength & ductility.
Most stock (oem) axles are made from 1039 steel-in the world of press on bearing type axle shafts, and 1050 steel-in the world of c-clip type axle shafts. The 1050 material has more carbon than the 1039 and is needed on the c-clip design to achieve a harder surface where the needle style bearing runs on the axle.
The factory (oem) is only interested in functional, non-performance, in-expensive axle shafts and keeps costs down by using economical materials and quick manufacturing methods such as; rolling the splines and induction hardening the shafts with a quick scan of the shaft, resulting in a shaft that is intended for non-performance driving to and from work, the store, or wherever.
The Dutchman line of flanged alloy axles are made from 1541-H material. 1541-H contains 1.5-2 percent manganese, which allows for a deeper case hardening and tighter grain structure-which ultimately makes for a "stronger than stock" axle shaft. In our line of performance front axles shafts, we use the 4340 "Chromoly" material which is thru hardenable. The design of the shaft and U-Joint ears necessitates the thru hardening process as it is not practical to induction harden the ears.
4340 vs. 1541-H. 4340 has more tensile strength than 1541-H, will take more twisting forces, but cannot take bending forces as well as 1541-H. Flanged axles are overhung beyond the wheel bearing and are subject to these bending forces-especially in the world of wider and/or larger diameter tires. The hard case and soft core design of a 1541-H flanged axle enable the shaft to bend, flex, and spring back. Properly executed, both 4340 "thru hardened" and an upgraded 1541-H "induction hardened" shaft can achieve nearly the same results in strength in the area of torsional strength (twist forces), but the design of an induction hardened shaft usually yields more bending (life) cycles than a thru hardened 4340 shaft. 4340 is more expensive than 1541-H, thus is reserved for the front shafts only which need the heat treated U-Joint ears for strength reasons.