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Joined: Apr 1999
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As I explained to you by phone, we are in the process of buying a new shot peen machine and we are considering changing the type and size of shot. Presently we are using 280 cast steel shot. We are considering using 230 cast steel shot or cut wire shot. I understand that cut wire is more expensive but will last longer. The only concern I have is if we use cut wire the saturation time will be the same as when using cast steel shot. As you know, the Boeing specification requires shot peening time to be saturation or coverage time "whichever is the longest". I know that I will reach coverage faster since we are shot peening aluminum parts but we have to shot peen until our almen strips reach saturation. If someone can answer my question, I will really appreciate it!
By the way, thanks for letting me know about your web page. It is great!

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The "Saturation Time" for cut wire shot can be very close, if not the same as that for cast shot if one choses the size and hardness of the cut wire shot properly. If one is able to accurately determine the average size of the cast media currently in use (used media will have a different average size than new media) as well as it's hardness, a cut wire size or work mix can be developed to perform similarly to the cast shot. We normally recommend CCW32 as an equivalent size to S280 shot. For any other questions, feel free to contact me at any time.
Bob Gillespie Phone: (216) 651-6758
Premier Shot Company Fax: (216) 651-6331

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04/13/99
Dear Jack,
There is a new Northrop Grumman internal document which will resolve your concerns in using Cut Wire Shot. If presently using 280 cast steel shot, the recommended Cres or Steel cut wire is SCW/CW - 28. The use of conditioned cut wire shot is recommended to reduce or eliminate metallic contamination and embedment, which in return reduces chemical cleaning of shot peened parts and dispersal of waste materials. In respect to revised peening times, The Boeing spec specifies that whenever 100 percent coverage is called out on an engineering drawing, the peening time shall be the longer of the time required for 100 percent part coverage or the time reqired for Almen strip saturation. Silvia, look at MEPS-15000-317 for more information.

Richard E. Buckholz
Materials Engineer - Lead
Northrop Grumman
BUCKHRI@mail.northgrum.com


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