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#218 08/19/09 06:16 PM
Joined: Apr 1999
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HELP. I need to confirm that I'm doing a process correctly. I'm peening the inner bore of a cylindrical aluminum part with stainless steel cut wire media. I must hone the hole after peening so that I meet a particular diameter and surface finish requirement. I'm told that I can remove material up to 10% of the peening intensity. The intensity range is 6-10 (i.e. .006-.010 inch). I have measured the inside diameter (id)of the hole before peening. If I use the 10% removal rule am I allowed to remove 0.001inch (actually .002 inch for a diameter since the .001 inch would be a surface or radius referral) or must I tell the honing department what my peening intensity was so they can remove 10%? For example, suppose my intensity was 7A (.007 inch). Can the honing department remove only .0007 inch (or .0014 inch diameter) ? The id before peening is 4.2504 inch. After peening it is 4.2523 inch. The other issue with this part is which measurement should be used to determine the allowable material removal. The inside diameter is measured before peen. After peen, it is sent to be honed. The part is measured after hone to insure it meets the dimensional requirements. The question is, may we use the pre-peen measurement to determine the acceptable amount of base metal that may be removed or do we need a post-peen, pre-hone measurement of the diameter on which to base the determination. To summarize: "Can the allowed maximum metal removal be based upon the maximum of the peening intensity range or must it be 10% of the actual intensity?"

Joined: May 1999
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AMS 2430 section 3.5.3.1 states the requirement as 10% of the minimum intensity value may be removed by honing. Other specifications state requirement as you may remove 10% of the nominal intensity. I know of no specification that permits the use of the maximum.

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I reviewed six shot peen specifications that our facility needs to comply to. Only one allows 10% of nominal arc height, the other five require 10% of the minimum arc height. I would say that it is safer to go with 10% of the MINIMUM arc height.
The specifications talk in terms of per surface, thus your stock removal would have to be from the actual post-peen size, not the pre-peen size. If the parts hole sizes are growing during peening, allowances will have to be made so that the final drawing size is met after peening and honing.

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Our practice is to use 10% of drawing nominal intensity. Using the 10% of drawing minimum intensity is doable as well. The danger there is having less removal amount available. The key is to pick one or the other for planning purposes, and stick with it. To use the actual intensity peened on the part, day to day, will introduce too much variation in the process. If hole is to be drilled/bored undersized prior to peening, an undersized hole diameter must be determined, so an intensity that the 10% rule is based must be selected. The removal amount is applied to the actual measured hole diameter after shotpeen. The trick is to hone to somewhere inside final hole tolerance, not remove too much material, and get to required finish, if required. Unfortunately, some trial and error happen for close tolerance holes


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