Countersink filler

[ArunKumar Bala]

Hi all,

Did anyone come across the usage of CSK filler in repair? If yes can we use it in both sides on a single part providing enough thickness on the part?

 

[rb1957]

yes, we (in the mod world) use CSK fillers (both ones we make from Cherry rivets and the ClickBond pre-formed ones) and I know some OEMs use them.

Using them in a double flush instance such as yours would be "odd" ... not Wrong, just unusual. "enough thickness" ... well that would depend on the fatigue environment but I'd apply the typical "2/3rd thickness" rule as applying to the total CSK depth (ie the sum of the CSK depths < 1/3 thickness).

But this is one person's opinion ... you need to talk to whoever is approving your work (the delegate).

Where are you ? (US, Europe, Africa, China, ...)
What type of plane ? (commercial, freight, ...)
If commercial, you may need to ask the OEM.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[SWComposites]

Arun - what exactly do you mean by "both sides of a single part"? both sides of a given joint member? or a countersink on both sides of a joint (different joint members)? if both sides of a given joint member, WHY? please show a picture of the particular issue. Also, you will need to do an appropriate stress analysis considering the increased countersink depths, reduced edge margins, etc.

 

[WKTaylor]

Some prior ET discussions...

Countersink Fillers 2004 ET discussion

https://www.eng-tips.com/viewthread.cfm?qid=101047

protruding head bolt in csk hole bearing stress Jan 2023

https://www.eng-tips.com/viewthread.cfm?qid=501512

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[3DDave]

I just picture a can from FIXIT Corp of "Countersink filler" "Don't accept cheap imitations!"
"

 

[ArunKumar Bala]

HI SWComposite, My issue is with a single part only. Not a joint. The issue here is during the assembly process, the operator has done the wrong countersink on the other side of the part. now we need to correct with doing countersink as per design and thinking of producing the csk filler on the other side of the part.

 

[SWComposites]

My opinion is - NO WAY. NO. You would be putting a countersink filler at the shear plane of the joint; the surface where bearing stress peaks. Unless you have specific test data (static and fatigue) to justify it (and I have never seen such), scrap the part.

 

[ArunKumar Bala]

Hi SWComposite, Thanks for your reply.

 

[rb1957]

Ok, different folks, different experience, different opinions ... neither is wrong.

We would repair the CSK and add the correct CSK if the was plenty of plain shank remaining (like 2/3rds the thickness), particularly if the part was not subject to a severe fatigue environment (like if it were an interior furnishing). On a pressure cabin skin we may do a DTA.

One way to fix is a freeze-fit plug, another might be to counter-bore the bad CSK ... simple stress analysis for the remaining thickness, DTA if needed, and fill counter-bore with a washer on ass'y.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.