High Tin Bronze Alloys for Gear Applications

The Bronze Alloy of choice for worm gears is C90700 (SAE65) High Tin Bronze.  This has been the predominant bronze alloy for gear manufacturing throughout the 20th century, and continues to prevail today.  But what is it that makes C907 such a superior alloy for this application? To develop a clearer understanding of this trend, we should examine a specific group of bronze alloys known as the High Tin Bronze Alloy Family.

Bronze Gear


High Tin Bronze Alloys are typically found in gear and high-strength bushing and bearing applications – especially where high strengths, low speeds, and heavy loads are present.  This alloy family includes the following:

  • C90300
  • C90500
  • C90700
  • C90810
  • C91000
  • C91100
  • C91300
  • C91600
  • C91700

High Tin Bronze Alloys include those which contain at least 6% tin.  The addition of tin to these alloys is designed to strengthen the bronze.

You may be asking yourself: what makes C907 so special?  After all, there are other bronze alloys with greater strength.

In gear applications, bronze parts act as sacrificial components.  Generally you are dealing with a bronze-to-steel mating application, where the bronze component is sacrificed to protect the more valuable steel component.  In these cases, the steel surfaces must always be harder than the bronze surfaces.  This principal can also be seen in bronze sleeve bearing applications which are designed to protect a steel shaft.

Over the years, Metallurgists have developed specific alloys to minimize wear of the bronze part, while at the same time still providing the benefits of the steel-to-bronze application.  These alloys have the strength to withstand the high loads of these applications and also yield a low coefficient of friction against steel.

Bronze Gear

In addition to the High Tin Bronze Alloys, it is common to see Aluminum Bronze Alloys and Manganese Bronze Alloys used in a similar fashion.  All of these alloys, once worn in, develop a low friction deposit of bronze on the mating steel parts.

The deposits from the Tin Bronze Alloys are more beneficial than deposits from either the Aluminum Bronzes or Manganese Bronzes.  The Aluminum Bronze deposits will eventually trigger aluminum oxide content on the steel parts. Manganese Bronze deposits, on the other hand, contain both aluminum and zinc.  Zinc oxide is highly abrasive, and can promote galling when mated with steel.

This is what separates the High Tin Bronze Alloys, particularly C90700, from the other bronze alloys in this application.  In fact, the deposits of High Tin Bronze asperities on the mating steel part actually decrease wear and friction forces over time.

National Bronze Mfg. Co. has been supplying gear manufacturers with C90700 (SAE65) and other “Gear Bronze Alloys” for over 100 years.  These alloys include C954, C863, C903, C905, as well as the C907 alloy.

What separates National Bronze Mfg. Co. from other metal service centers is our technical expertise of the bronze alloys, as well as our full production capabilities.  While we are a leading distributor of bronze and other copper-based alloys, we have also been producing quality bronze parts through the production machining division of our company.

Gear Manufacturers have been taking advantage of our diverse product lines and capabilities in various ways.  An exceptionally beneficial component is our bronze gear blank product line.  We will machine various bronze alloys into slightly over sized blanks, allowing you to spend your time on the more complex machining processes associated with gears.  This not only frees up valuable machine time, but lowers material scrap and overall production costs.

bronze gear blank

Let us configure a specific combination of products and services to help make your company more efficient and competitive.  Follow the link below to contact an experienced Sales Engineer from National Bronze Mfg. Co. so we can start developing customized bronze gear solutions for you today.

Contact Us Today



Add a Comment

Your email address will not be published. Required fields are marked *