Metric Steel

 Metric Steel FAQs

1. What Exactly is “Metric Steel”?

Metric steel refers to steel products manufactured and measured according to International Organization for Standardization (ISO) or metric-based national standards (like DIN in Germany or JIS in Japan). Unlike Imperial steel, which uses inches and fractions, metric steel dimensions are expressed in millimeters (mm).

2. Is Metric Stainless Steel?

No. “Metric” simply describes the unit of measurement (millimeters) used for the dimensions of the steel, while “Stainless Steel” refers to the chemical composition of the metal.

Specialty Steel Company stocks both metric carbon/alloy steels (which can rust) and metric stainless steels (which are rust-resistant). To ensure you are ordering stainless material, you must specify a grade like 316L or Duplex.

3. What is The Difference Between Alloys, Stainless Steels, and Chrome-Plated Bars?

While these terms are often used together, they refer to fundamental differences in how the steel is manufactured and how it performs in various environments. Alloy Steels, such as 4140 and 4150, are carbon steels enhanced with specific elements like chromium and molybdenum to significantly increase overall strength and hardness. While they are incredibly tough and ideal for heavy-duty structural use, they lack natural corrosion resistance and will rust if left exposed to the elements.

In contrast, Stainless Steels like 316L and Duplex contain high levels of chromium, usually at least 10.5%, which creates a unique, self-healing surface layer that actively prevents rust. This makes them the premier choice for wet, medical, or chemical environments where hygiene and durability are critical. 

Finally, Chrome-Plated Bars (including I.H.C.P. and C.P.O. varieties) are typically standard carbon or alloy steel bars that have been electroplated with a thin, external layer of chrome. This process results in a very smooth, mirror-like, and hard exterior perfect for hydraulic parts; however, unlike stainless steel, the core of the bar remains standard steel and does not possess inherent rust resistance throughout.

4. How Do Threaded Rods Differ From Standard Bar Stock?

The primary difference between these products lies in their surface finish and intended mechanical application. Threaded Rod, such as the B7 Alloy variety, features continuous helical grooves or threads along its entire length, making it ideal for use with nuts to fasten components together or to provide structural tension. 

In contrast, Bar Stock (Shafting) consists of smooth, round bars designed for motion and precision. Specifically, our TGP (Turned, Ground, and Polished) bars are engineered for high-accuracy applications where a perfectly smooth, consistent surface is required to fit seamlessly into bearings, bushings, or sleeves.

5. What is Keystock, and Why Is It Categorized Differently?

Keystock is a square or rectangular bar used specifically to lock a rotating machine element (like a gear or pulley) onto a shaft. Unlike our other bars, Specialty Steel’s 1018 CD Keystock is manufactured with an undersized tolerance. This ensures that the key fits snugly into a pre-cut “keyway” slot without needing heavy machining or filing, which is critical for mechanical power transmission.

6. Which Steel is The Strongest?

In terms of raw tensile strength and mechanical durability, the 4140 and 4150 heat-treated TGP Alloy Shafting is generally the strongest material on this list. Because these bars are pre-hardened to a Rockwell hardness of Rc 28/34, they offer a superior balance of high yield strength and toughness compared to standard carbon steels like 1018. 

While Duplex Stainless Steel is also exceptionally strong and outperforms standard 316L stainless, it is typically chosen for its resistance to extreme corrosion rather than pure mechanical load-bearing. 

Similarly, the B7 Threaded Rod is a high-strength alloy designed for heavy-duty tension, but for precision rotating parts or shafts that must resist deflection and wear, the heat-treated 4140/4150 rounds are the industry standard for strength.