H

HighSchoolBuilders

Well Known Member
Hi all,

Does anyone know what is the tolerance for countersink? I was countersinking on the Z brackets for my tank, I didn't enlarge the hole, but it definitely went deeper than the rivet head. Should I replace the bracket?

Many thanks!
Hank
 
This is the specification --

HighSchoolBuilders said:
Hi all,

Does anyone know what is the tolerance for countersink? I was countersinking on the Z brackets for my tank, I didn't enlarge the hole, but it definitely went deeper than the rivet head. Should I replace the bracket?

Many thanks!
Hank
Click to expand...

3.3.6 Countersunk rivet head flushness. Unless otherwise specified on the engineering drawing or specification, flushness limits shall be 0.010 inch above to 0.005 inch below the material surface. Countersink diameters are provided in Table IV for reference

The entire document I created is now on Vans web site...

http://www.vansaircraft.com/public/Specs.htm
 
HighSchoolBuilders said:
Hi all,

Does anyone know what is the tolerance for countersink? I was countersinking on the Z brackets for my tank, I didn't enlarge the hole, but it definitely went deeper than the rivet head. Should I replace the bracket?

Many thanks!
Hank
Click to expand...

I wouldn't. The countersunk rivets are not structual... they simply hold the nutplates in place. I'd slap a rivet in there and move on. May even try an "oops" rivet.

Build on.
 
Do you have access to a Lathe, you can make up a countersink filler out of some 7075 T6 material to the depth that you CSK by mistake, then CSK the filler to the required depth of the rivets your using, use the filler under the head of the rivet and away you go, the other thing to keep in mind is that you haven't knife edged the material, one rivet might be OK depending on where it is.. If you have alodine 1200 and a decent primer, that will help against the possibility of corrosion later on.

Nick..
 
Might be possible to countersink a bit more and use an AN426-AD5 rivet in there too...

Phil
 
Another approach

I have also seen Van's recommend using JB Weld to fill the hole, then redo the countersink at the correct depth. I was surprised that JB weld is so strong.
 
Many thanks! I don't think I can get a -5 in because it's limited to the size of the platenut. I will see if I can get a photo and see what you guys think, thanks!

Hank
 
Couple of things you can do. Firstly, if it is only slightly oversunk then it will pull in when you squeeze it. Secondly, if it is deeper but the hole is not enlarged then you can make a drift by inverting another rivet on top and squeezing the 2 together.

Sent you a PM.
 
paul330 said:
you can make a drift by inverting another rivet on top and squeezing the 2 together.
Click to expand...

I can second that inverted rivet idea. On my QB fuse as it came from the factory, some of the rivets holding the seat ribs to the spar flange were loose due to a slightly over-deep countersink. An extra squeeze with the inverted CS rivet on top easily fixed it.
 
shuttle said:
I can second that inverted rivet idea. On my QB fuse as it came from the factory, some of the rivets holding the seat ribs to the spar flange were loose due to a slightly over-deep countersink. An extra squeeze with the inverted CS rivet on top easily fixed it.
Click to expand...

An other way to do this that is easier to control (in my opinion), if you have access to a whitney hole punch. Make a guess at how deeply you over countersunk. Punch a slug in proper thickness material with the hand punch, at a diameter that is close to the diam. of the rivet head. Use the slug as a spacer on top of the recessed rivet head (you can tape it in place if necessary).

Not that I have ever had to do this my self....
 
Thanks Scott,

It's actually not very difficult to control at all. There was one step in my process that I didn't mention that simplifies things. The 'inverted rivet' that I used was heavily pre-squeezed on its own to flatten it before I used it to fix the loose rivets.

Using a flattened rivet means you have an exact match to the head size of the rivet you are wanting to 'fix' and no need to tape it in place as the over-countersunk hole privides an edge to keep the flattened rivet centred.
 
I have been told that if every other rivet in Vans RVs didn't exist the plane would still be a flyable and strong aircraft.
 
Z-bracket rivet countersinks

Hank,
The advice you've gotten here is good for countersink boo-boos in general. I just finished my z-brackets last night. On my very first countersink, the inside one, on the spar :eek: , I stupidly countersunk the wrong side of the spar!:mad:

Rather than publish my stupidity on these forums I chose to privately email some of the folks here that I trust.

The solution for the z-bracket countersinks was to countersink the proper side and build on.

Yes my left tank inboard z-bracket is attached to platenuts held on the spar with rivets in improperly countersunk holes!!!

For platenuts, the rivets only hold the platenuts in place so the bolts can be threaded into the platenuts. Think about it. The rivets on platenuts don't carry the load...at least in this application.

As others have said...BUILD ON!

P.S. And to think, I had a goal when I started to never have to re-do any rivets! Huh! That went out the window on the horizontal stabilizer.
 
shuttle said:
Using a flattened rivet means you have an exact match to the head size of the rivet you are wanting to 'fix' and no need to tape it in place as the over-countersunk hole privides an edge to keep the flattened rivet centred.
Click to expand...

It works the same way if using a punched slug.
The reason for the tape comment is that sometimes the hole you are working on is on a vertical surface or even upside down. The flat slug is very easy to tape in place in this situation.
 
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