What is Shot Peening and Why is it Useful?

Christa was over a second a lap faster with no other changes after we put everything back together.  She reported the ride was a little better. We guess there is something to this.  We have shot peened Honda front suspension uprights and springs to get a longer life out of them before using the same principle.

When you apply stress to metal, particularly when it’s cold, it work hardens, some metals do this more than others. This is because the stress causes the grain of the metal to become finer. Processes like forging, roll forming and flow forming work in much the same manner.

Some shot peening equipment uses compressed air to propel the shot to the part being shot peened, much like in sandblasting.  Other methods include centrifugal flinging of the shot at a part to control its velocity precisely.

Here is a large-size shot peening machine that can treat big parts.


  1. For ring and pinion prep, would there be any advantage of prepping used parts that have had the surfaces worn in but not abused or would it just be better to start from zero?

    1. As a certified mecanical engineering consultant specializing in failure analysis for a few wonderful decades, I specified shotpeening for many applications with fatigue failures completely eliminated in many cases. Elimination means an “infinite fatigue life”.

      I actualy tried to do what you are asking, shot peen an industrial part that had already seen millions of cycles. And unlike a new part, the peening did not prevent an early fatigue failure.

      For those more interested in the subject, this link shows graphically what fatigue life is all about, copy & paste:


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