Tempering Shafts - Q&A Question

The following question was recently posted to the Q&A forum.

I don’t want to presume to outcome to the question, but do want to make a few metallurgically related comments:

  1. Quenching and tempering steel to achieve a higher yield strength requires that the steel have a sufficiently high carbon/alloy content for the formation of non-equilibrium microstructures. So unless the shafts are 1040, or perhaps a 41 or 43 series of steel, you’re not likely to see any benefit… and I’m doubting that VEX used a fancy alloy for them.

  2. Heat treating will certainly affect your surface finish and possibly dimensional tolerances.

  3. Depending on how the shafts were manufactured, heat treating may actually reduce their yield strength. I’m guessing there is a good chance that the shafts were cold-rolled, resulting in some work hardening taking place. Heating to the austenitic zone will result in crystal regrowth and a loss of the cold worked strength.

  4. Heat treating aluminum follows a rather different process… you could actually quench and temper the aluminum to make it softer and more deformable, and then either allow it to naturally age or artificially age it to regain yield strength.

  5. Regardless of the official answer from VEX (and my “no-fun” commentary, above), I highly encourage you to experiment with heat treating both the steel and aluminum parts. Recognize that the parts may no longer be competition-legal, but you’ll likely have come up with some interesting observations and conclusions and learned a few things about metallurgy en route. I’d be delighted to see some experimental results showing that you were able to increase yield strength in the shafts by quenching and tempering the steel, but even more interested to see the experiment design and procedure that you used.

Never let a VEX rule stand in your way of exploration… go ahead and sacrifice a few shafts to see if it works!


Lets not even forget that heat treating messes with the straightness of the axle. No one likes working with bent axles.

I dare you to make canister Damascus with VEX parts and carbon shavings and see what you can make with it xD