Stress Coining 3

[bails63]

Does anyone know the difference between stress coining a hole and cold working a hole? I am machining a fitting from aluminum plate have a requirement that states that no stress coining is allowed in any holes located with the axis normal to the ST direction. I'm not familiar with the term stress coining. Did some basic research and it sounds like it is similar to cold working.

 

[rb1957]

coining is compressing the faces of the plate around the hole.

cold working a hole is expanding the hole bore.

 

[bails63]

so that would tend to thin the plate by a very small amount around the hole. How would one go about doing that when machining a fitting? I'm trying to figure out the rational behind the requirement of no stress coining. Doesn't sound like something you would normally do unless you had a specific requirement.

 

[redpicker]

It sounds like the specific requriement is not to do it.

Perhaps the end user has had problems with hole size and/or trueness being affected by this on previous parts and has included this note so the fabricator is aware that they are not to compress the faces of the plate around the hole for any reason. Or, maybe a previous vendor used this technique to bring out of tolerance holes into tolerance which created unintended problems. Regardless, you seem to have done your due dilligence in finding out what is prohibited and should be able to comply.

rp

 

[bails63]

Thanks for your help.

 

[rb1957]

it sounds like "over-specification" ... ie don't do something you wouldn't normally do ... if the limitation wasn't there you'd probably never have gotten any interest in coining !

 

[mfgenggear]

some fabricators would repair the holes if it where over sized from machining or punching or what ever. by peening the the edges of the holes. This would reduce the diameter to size, which is not allowed. unless it is stated in Eng drawing that it is.

Mfgenggear

 

[mfgenggear]

RP

sorry I should have read your post better, yes I agree with your statement, sorry for repeating the post.

Take Care

Mfgenggear