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Knife edge
2

Knife edge

Knife edge

(OP)
hi,

could any one tell me what is meant by Knife edge condition and feather edge condition in relation to Aircraft structures.How to avoid these?

Thanks,

Hanosh

RE: Knife edge

Knife edge, in one meaning of the phrase, means there is little to no straight bore. Drill a countersunk hole in a sheet or plate, you get a countersink, and a straight bore hole. If the countersink is too big, so there is no straight bore in the hole, then you get a knife edge.  Side
 view of a hole countersunk in a thin sheet--see how sharp
 the edge between the countersink and the bottom horizontal
 surface? that's the knife edge:

           _________                ________________
                    \              /
                     \            /
                      \          /
            ___________\        /______________

no idea about feather edge.

RE: Knife edge

Knife-edging is when the rivet/fastener countersink is more than 2/3rds the thickness of the sheet ... this is general practise.  i'd guess feather edge means that the CSK is >=100% of the thickness

RE: Knife edge

to avoid a knife edge, you need to dimple the skins under the head of the countersunk fastener.

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RE: Knife edge

Sorry about my little stick drawing; it looked ok in the Preview.

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