Technical Memo

Which Gear to use; Cast Gears or Forged Fabricated

May 22, 2007

As President of HMC I have continually stressed to my organization the importance of promoting products we believe in.

HMC has gained extensive experience over many years in designing, specifying, and manufacturing, Cast and or Forged Fabricated Gears; both offering comparable service life when specifications and material integrity are equal and the application is suitable.

One of the key essentials to HMC's success with Cast Gears is; we always emphasize the importance for Level 1 Castings when critical custom gears are involved. HMC normally will not specify Commercial Grade Castings for Large Critical Gear Applications.

HMC learned many years ago that most Commercial Grade Castings often require numerous weld repairs after their pour and quench. These repairs frequently end up in the tooth and root areas. Weld repairs when required on castings must be performed at pre-heat temperatures upwards of 500 Degrees Fahrenheit by human beings. Because of these unpleasant and difficult working conditions it is likely that inadequate repairs and green welds can and do occur thus coming back to often haunt the manufacturer and end user of the gear.

HMC's specification for Large Critical Gears is ASTM Level 1 Acceptance. Our Designs will, when possible, have large liberal radii incorporated to mitigate shrinkage problems; the biggest cause of flaws in castings.

HMC began using Forged Fabricated Gears in the early 1970's when hit by the 1973 Oil Embargo. During this time, Finish Goods requirements skyrocketed in price, and lead times doubled. Most industries; Mining, Cement, Power Generation, and Steel were acclimated to primarily using cast gear components during that era and HMC customarily manufactured their gears at that time from castings. (Please see "Total Dedication to Your Needs"- HMC's Casting Sales Brochure).

HMC is not advocating Cast over Forged or vice versa. We are simply offering workable solutions for our customer's.

Essentials for Successful Quality Forged Fabricated Gears:

1. Adequately and Properly Designed

2. 21st Century Thru Hardened Seamless Forged Rings made from Alloy Steels and 100% UT inspected by the Forging Company; assuring no flaws or inclusions of any kind exist. And if there are flaws; the Ring is Scrapped. End of Story!

3. Perform all Fabrication and Welding Processes using prescribed pre-heat - hold heat - and stress relieving temperatures

4. And Machine to meet HMC's exacting Advanced Technology Gearing Tolerances; (ask for a copy of HMC's Advanced Technology Gearing Bulletin).

HMC's Forged Gears will offer comparable service to Cast Gears. When manufactured to our designs and specifications and installed and aligned in new machinery; HMC guarantees with confidence our Quality Forged Fabricated Gears. We believe in our Welding Staff and our Forged Fabricated Gears. In fact we will put our Welding Staff and Gears against any in North America.

When a Gear; Cast or Forged is installed and adequately aligned in New Machinery such as a Mill, they will both perform comparably for many years because they are given the opportunity to wear gradually and comply with the gradual deterioration and misalignment the machinery experiences over time.

In comparison; when a New Gear is installed in Tired Machinery; with extensive misalignment, the gear; Cast or Forged, unable to instantly comply; will experience the uneven loading forces; deterioration and misalignment, which can result in immediate and significant tooth wear, cracks and breakage, or even separation in certain transition areas of the gear.

It is HMC's confirmed belief; after investigating many premature gear failures that; when new gears are improperly installed the gear can lose a significant portion of their service life; sometimes within a few hours. There have been situations where Forged Fabricated Gears received a bad reputation when used to replace original Cast Gears after many years of service. The real problem generally has been improper installation and Old Tired Machinery.

Our 7/24 Hour Manufacturing Infrastructure is always available to you and only a phone or e-mail message away. Please contact us any time we can be of assistance to you on any matter; (Technical Information, Custom Replacement Parts - (Normal or Rush)!