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#249 - 01/21/09 03:18 PM Do peened holes get larger or smaller?
Jack Champaigne Offline

Registered: 04/20/99
Posts: 317
Loc: Mishawaka, IN, USA
I was recently asked if peened holes increase or decrease in diameter as a result of peening. My meager experience suggests that holes get larger but I'm wondering if there are materials or peening parameters that would actually cause the hole to get smaller. I realize that the material thickness is an imporant parameter i.e. thick material (deep hole) may not change very much at all. Can anyone else add experience to this question?

#250 - 01/21/09 05:37 PM Re: Do peened holes get larger or smaller?
mohammed Offline

Registered: 03/13/07
Posts: 3
Loc: montereal ,canada
yes it will degrease hole dia and we used shot peening to decrease a dia was oversize
so it will be smaller simply cause u denting the surface and there is a material pumped out from the surface and thats looks like a peaks but if u use any polishing after, u will go back to your intial dia.
also if your nozzle is not straight u will have ovality problem and you will be confused if the dia is samller or bigger actually it is oval

please note that always check your material kind and thickness and intensity goes with that

#251 - 08/17/09 01:22 PM Re: Do peened holes get larger or smaller?
michael.a.sorenson2 Offline

Registered: 11/29/04
Posts: 3
Loc: Renton, WA, USA
Jack - in most cases, I have seen examples where hole sizes have grown after shotpeen. I believe this to be due to overall shotpeen growth factors. It can become more pronounced where depth of hole is thin, and intensity is high (more shotpeen growth). This becomes an issue for close tolerance holes (hole size range less than .0030), where if hole is not undersized prior to shotpeen and drilled/bored to full size, then after shotpeen, hole size can grow out of tolerance. However, I have seen cases where hole sizes have shrunk. It has been at lower intensities (.004a/.007a) - I believe shotpeen growth is so small, and the apparent shrinkage could be attributed to peaks made by the shotpeen indentations only. If intensity was higher, growth would be more, and more than enough than the apparent shrinkage due to the peaks of peening indentations. I would be curious to see other examples of this from others

#252 - 08/17/09 02:53 PM Re: Do peened holes get larger or smaller?
Socrates Offline

Registered: 02/20/06
Posts: 108
Michael's comments agree with shot peening theory. An internal 'ring' of compressed material is generated by shot peening. Some of the residual stress in this ring has to be relieved by increasing the diameter of the ring - generating a balancing tensile force in the underlying material. Hence the 'real' hole diameter increases. 'Apparent' diameter change depends on the induced change in surface roughness. This depends on the pre-peening roughness and the shot size.


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