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Ductile Iron Machining Advantages

Posted by Penticton Foundry on June 1, 2016

Part 2 in Our Series of Ductile Iron vs Steel

In part 1 of our series on ductile iron vs steel we did a general comparison of the two alloys to determine which might Cable drums for the winch industry made of ductile the better option for a given application.  The blog was intended to be a generic overview.  In this second part, we specifically take a brief look at how ductile iron and steel match up when it comes to machining.

As a side note: Check out this blog we wrote comparing ductile iron and gray iron.

Ductile iron has the following machining advantages compared to steel:

  1. Greater depth to diameter drilling ratios
  2. Faster feed rates 
  3. Higher spindle speeds 
  4. Extended tool life

When discussing the intermediate-strength grades of ductile iron, the ductile iron has a better machinability than steel because:

  • The high amount of silicon in the ductile iron decreases the toughness of the ferrite (the metal matrix component).
  • The graphite spheres give ductile iron its free-machining properties due to lubrication by the graphite.

These two “properties” are why ductile iron has greater depth diameter drilling ratios, faster feed rates, higher spindle speeds and extended tool life.

Clutch housing made in ductile iron.For more information on machining ductile iron one should consult the Machinery Handbook and/or your cutting-tool supplier.

Want to read more about ductile iron?  Then check out our ductile iron webpage.

Also, for more technical information on ductile iron, visit the Ductile Iron Society at  This website offers a wealth of information on the technology, properties, and characteristics of ductile iron.