rivet shaving 2

[BBrazil]

I am looking to get correct information on rivet shaving. I work for a Aerospace company in stockton ca. I know the process being used on winglets is incorrect. ME's and QE's dont want to deal with it.
It is my understanding the indents on the heads of a flush clinch rivets should still show and that the rivet shouldnt be shaved more than .010.
What is happening is the Techs are setting the rivets countersink low so the rivet will set high and then shave them flush leaving the dia. of the head now reduced, thus jeopardizing the integrity of the rivit as it was designed.
The parts I build are for corporate jets and do fall under SURFACE PROFILE (AIRFLOW) specs. Spoilerons and Winglets. I will replace a rivet I dont think is correct because I want to do the best I possibly can. I am working on a degree in Engineering, I want have the knowledge to not let this kind of laziness jeopardize apart I am involved in designing or building.
Please let me know if I am wrong.
BBrazil

 

[rb1957]

where in your rivet process are tech's allowed to "set the CSK low" ? there should be an acceptable depth range for the CSK, defined either by your process spec, or by the relevant MIL-SPEC. i would be concerned if in shaving the heads they're leaving less than a reduced head (1097) rivet.

 

[RPstress]

Unless the fastener is designed for milling flush, this sort of thing should be controlled and probably explicitly inspected (by measuring the diameter of what's left of the head). There are some rivets even smaller than the short head shear NAS 1097s: the Allfast crown flush rivets are probably about as shallow headed as anything should be (

http://www.allfastinc.com).

To reiterate, some fasteners are designed with milling flush in mind. If it's done right it's fine.

 

[WKTaylor]

BBrazil..

What do You mean by "clinch rivet"??

Are these blind rivets or solid rivets??

If You are milling solid rivet heads then what is the design [certification] requirement for the rivet installation?

If you are milling blind rivet heads, then there are a heap-O-other troubles possible that would be considered major structural concnerns by ALL of the blind fastener manufacturers.

Note: I used to work for a company that had a policy of deliberately machining all countersinks to the depth of an NAS1097 [shear-head]; then installed only MS20426 flush-tension head solid rivets [sat way above flush when installed]; then every external rivet was microshaved flush to the skin; then every bare rivet head was brush-alodined. The process produced a "slick skin appearance" but took a lot of tedious man-hours.

When the company was going bankrupt due to the costs of manufacturing, and asked for cost-cutting ideas, I asked why don't we install the "new" NAS1097 rivets and eliminate all countersinking: would save hundreds of M-hours per acft. I got a cold stare and was told that the aircraft was certificated with the rivet-process "as-is" and that using NAS1097s might constitute a major revision to the design. My only answer to that reply was to [quietly] begin looking for a new job.

OH Yeah...

Regards, Wil Taylor

 

[rb1957]

i just love your stories Will; they remind me that everywhere is nearly equally effed up.

btw, installing 1097s in a 1097 CSK would reduce (eliminate?) the shaving hours (not the CSKing hours).

 

[WKTaylor]

Rb1957...

Yep... except it would have saved shaving AND brush-alodine Man-Hrs... not to mention all the environmental and health "issues" [we now know] regarding exosure to alodine.


Regards, Wil Taylor

 

[rb1957]

ah, alodine puts hair on y'r chest ! take some in your coffee (probably better than that sugar substitute stuff) give y'r kids a teaspoon morning and night (just like cod liver oil, yech)

 

[BBrazil]

Thanks rb1957, Unfortunately there is no tech direction to set csk low. The MID tells the techs to set the rivet to fall within a +/- height and mentions no shaving.The stems pull short so they set them high then shave them flush, obviously reducing the dia. of the head but now the stem is flush with the head and surface.We as Techs are not allowed to use drawing to build to. We may be givin a mylar with just a pattern and hole locations to use as a template.The Inspectors we have in this company have no training or knowledge of rivets and how they work and should be used not to mention how a part should be built. It is so easy to get things past inspection or as I have seen hiding things so the part will make it to ship.The M.E.s in this company dont know either, As long as the part gets bought off by the inspector they could care less.

 

[BBrazil]

Thanks RPstress,
I am aware that some rivets are designed to shave and some not to be shaved. This company does not hire qualified people, (they'd have to pay them to much)Most have no clue. I use the 1097 rivet on the spoilers I build and dont shave them. I set them where a quick scuff with some sandpaper cleans them up nicely. Just as you say "If its done right its fine"

 

[BBrazil]

Thanks wktaylor,
Yes, a clinch rivet is a blind rivet. Blind rivet shaving does create tons of issues, most all negative. This is why I questioned the process, These parts are winglets. Fully exposed to high stresses. It s only obvious to me there is a potential risk in the way the riveting is performed but will anyone stand up to seriously looking at it.......NO!!! Really, I get the same kind of reaction as you did.
By the way, I am quietly lookig for another job. Unfortunately this isnt the best economic time to start a new job.

 

[WKTaylor]

Darn-it...

I finally figured-out what RB1957 meant when he said in reply to me "eliminate countersinking???"...

My hand was faster than my brain... again. obviously I meant to say NAS1097s [in proper countersinks] eliminate need for microshaving... not countersinking.

---------
BBrazil... a sneaky way to end run this problem may be to change blind Rivet P/Ns to accomodate the manufaturing style of Your group.

NAS9303 [aluminum sleeve, steel or CRES pin] and NAS9309 [monel bare or aluminum coated] are NOMINAL diameter rivets with a head style [shape/size when installed] very similar to the NAS1097. The 1/64" OS versions [NAS9305 and NAS9311] have a head-style that is slightly deeper than a 1097... but significantly shallower than the MS20426.

Also, my favorite: have You ever used, or even heard-of the blind rivet head style "flanged-dome head" [lovingly called the "Unisink" by CHERRY, NAS9306/NAS9312]? It combines a tiny countersink with a VERY low-height protruding head. Great for thin skin installation, with allowables that are essentially identical to the equivalent protruding head OS blinds [Ref procurement specs NAS1686, NAS1687].



Regards, Wil Taylor

 

[RPstress]

Milling blind rivet heads looks decidedly dodgy to me. There's usually a locking ring that helps retain the pin. Damaging that would be dangerous. Exactly what is the rivet spec?

 

[BBrazil]

To make any changes in parts or part #'s would take an act of God. You are talking First Articles Engineering changes that nobody wants to do in the company I work for ....its not cost effective when they can push a part out the door. Not only changes for the co. I work for but the customer would have to do the same , besides , they havent a clue as to what is really happening here. I could lose my job I if I push to hard. I have succeeded in bringing it to certain persons in managment including a QE. Yesterday I went to a completed winglet with calipers in hand and measured the diameter of some of the rivets ( HC6224-4-03 FAA AUTHORIZATION BASIS:TSO-C148 BLIND RIVET HUCK CLINCH )The diameter of the rivet in the part is .160 (that has been shaved) A fresh rivet out of a new bag of 100 (ALCOA fastening systems) measures .182. I witnessed a guy trying to replace one of these rivets after shaving, as he tried to punch the stem in the whole head punched in through the hole.

 

[Kwan]

It's always too expensive to correct the problem. Haha until the company has to pay lawyers and victims.

 

[berkshire]

BBrazil (Aerospace)
It would appear to me that an audit by the FAA at your facility is overdue.
Especially if the items you have been complaining about were known to them, ( But you would not tell them, Right?)
B.E.

 

[BBrazil]

Yes, to expensive, but much cheaper than paying lawyers and victims.
This company is a AS9200 Boeing certified facility and Audits happen every year. Its amazing how good the company can put certain programs under the radar.
I could lose my job if it was known i said anything. In this economy that wouldnt be a good thing for my family. I dont recall the FAA ever doing an Audit there, but you are right, its way overdue.