In-House Hardness Testing at Heinz Engineering

At Heinz Engineering, we pay close attention to customer feedback and, when feasible, adjust our services accordingly. 

Lately, there’s been an increased demand for hardness testing from our aerospace customers. And what better way to meet this demand than bringing the capability in-house at our precision machine shop?

What Is Hardness Testing and How Does It Work?

Hardness testing is a method for determining the hardness of a material based on the Rockwell scale. It confirms that a piece of material is strong enough to meet customer specifications. Sometimes, a material can be purchased and used as is; other times, hardness testing tells us that it needs to be hardened (i.e., heat treated) or softened (i.e., annealed). 

We typically perform hardness testing on stainless steel and aluminum, but sometimes we’re asked to test other metals, like Inconel. 

During hardness testing, an indenter is pushed into a material until the material pushes back, creating a small dimple. Once the machine carrying out the testing receives the pushback, it calculates the hardness. The dimple is left in place—proof that the testing was completed. 

It’s a best practice to conduct hardness testing before any outside process except heat treating—a technique widely used to harden materials for aerospace machining. Hardness testing may be performed to confirm that a material meets critical specifications post-heat treating. However, conducting hardness testing after a process like plating, for example, can compromise the part, as the indenter may cause cracks when it pierces through the plating. 

Using the Rockwell scale 

Customers can request that we use any of the six conversion scales derived from the Rockwell hardness scale: HRC, HRA, HRB, HR45N, HR30N, and HR15N.

The Rockwell C scale (HRC) and the Rockwell B scale (HRB) are the most common choices. We use a cone-shaped diamond indenter for the former and a ⅙” ball indenter for the latter.  

Why Is Hardness Testing Important in Aerospace Machining? 

Hardness testing is performed for various high-risk aerospace applications, such as the parts that make up an aircraft wing.

An aircraft wing is constantly under stress, and there are only so many flight hours before certain parts need to be replaced. Parts that are too soft or too rigid fatigue faster and wear out more quickly—and that’s if they even function properly to begin with.

However, thanks to hardness testing, aircraft manufacturers can be confident that parts have just the right amount of hardness to sustain the expected amount of stress during their lifespans. 

How You Benefit from In-House Hardness Testing

Heinz Engineering successfully outsourced hardness testing to a trusted vendor for many years. But it recently became clear that we could provide more value to our customers by offering this capability in-house. 

Since we started conducting hardness testing at our precision machine shop, our customers have seen lower prices and faster lead times. It’s just one more way Heinz Engineering is consolidating operations under one roof to improve efficiency. 

Request a quote for aerospace machining and benefit from our in-house hardness testing capability.