Double Flush - How Flush?

In several places AN426 rivets are placed where 'double flush' countersinking is called for on both (opposite) sides of two pieces.

My querry: Does the shop head have to be absolutely level with the surrounding surface, or is severe and total rivet squeezing which leaves a bit of the shop head above the surrounding surface standing out a bit OK?

Have you left the shop heads that way, or do you file or somehow cut/file them down to absolute level?

It depends on how they are to be used - what parts they go up against. Look ahead in the plans each time and to see how they will be used.

I found the best way to get them absolutly level was to:

1. Make sure the countersink is deep enough.
2. Squeeze the heck out of them!
3. Polish down any material standing proud using a coarse ScotchBrite disk in a die grinder.

Works for me..........

John

I almost forgot - hit the spot with a little primer because you will have eaten into the Alclad coat.

JohnF said:

Have you left the shop heads that way, or do you file or somehow cut/file them down to absolute level?

Click to expand...

It depends on the need for clearance. It is often possible to file the shop head down close to flush without marring the part.

Jeff

Get them the best you can do, but do not squeeze them so hard that the bearing seizes.

After all is done, you can look at the adjoining part and file down the shop head of the rivet a bit, if needed. Put a piece of tape over the shop head, and file it thru the tape. The surrounding metal will be protected from your file scratches via the tape.