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Countersink Ooops!

T

Topturn

Active Member
Been working on preparing and priming the parts for the Anti-Servo Tabs this week and today tackled the countersinking of the holes on the HS-1220 control horns.

I set my countersink tool on some scrap and off I went no issues on the first horn then onto the second one and on the first hole the sink is too deep for an AN426AD3-3.5 rivet but a 'bigger/fatter' AN426AD4-4 fits a treat and is flush to the surface. I know I'll need to enlarge the rivet hole in the HS 1222 rib to make it fit but my question is it OK to do this?

No idea why the tool over sunk the hole but will proceed with extreme caution when using the sink again.

Couple of photos

http://www.build12.co.uk/albums/Pages/empennage.html#35
http://www.build12.co.uk/albums/Pages/empennage.html#36
 
The countersink went too deep because you were countersinking on the edge. The cage was not resting flat. Yep, you have to be careful countersinking any hole near an edge.
 
I suspect the bigger rivet will be fine, but check with Van's tech support to be sure. I had a bad time with those horns too. The problem is you have to work with those things before you have gained much experience. I ordered new horns, they are pretty cheap.
 
Good news from my kit inspector he's seen the photos and OK'd using the larger rivet in this location.
 
When CS-ing on the edge try butting a second piece of material up to the work to provide a level surface for the face of the tool. Van's pricing for replacement parts is very reasonable. We're working on the last kit and our "wall of shame" tally is $353.
 
Topturn...One thing that I noticed is that once the cutter starts to enlarge the back hole, the centering pin starts to wobble and really makes things a lot worse so that only a little over drilling makes a big hole. Sometimes I use a spare piece of aluminum or even wood with holes drilled to match the centering pin and a second or third hole for securing the two pieces together. This tends to keep over drilling wobble down.

I also use my left hand to secure the stop while drilling with my right hand.

Regards,
Jeff
 
Wonder if anyone can provide an insight in to which number Countersink suits which type of rivet as I’m moving on to the stabilator and don’t want to make any costly mistakes in both time and financial terms. In my Countersink Kit I have the following, is it as simple as matching up to the drill size required to make / match / final drill the hole?

# 40 -
# 30 -
# 27 -
# 30 (120 degree) –

I feel like I’m asking loads of questions at the moment but hope to be able to put something back at some point

Just found a short video online helps with setting up the countersink cage
 
Last edited:
Jason,

I finished the stabilator last week and there were no surprises although I ended up drilling out one of the ribs that had the control horn attached because I was unhappy with a small gap between the two. I squeezed the pieces together more tightly than a cleco could while my wife squeezed the rivets. It came out looking much better and I am happier! This was also the first time I had to drill out the pulled rivets which I found to be much easier than the squeezed rivets.

Aside from the CS4-4 rivets which require the 120 degree countersink,(be careful on the stablilator spar) all of the others seem to be no brainers and it is just a matter of matching the bit sizes as you said.

Mark Misage

www.n624rv.blogspot.com
 
Decided to do some countersinking before coming to work and it freaks me out everytime as I keep thinking one mistake and that's an expensive piece of scrap I've just made. Having said that I'm a little happier with the experience tonight
 
Topturn said:
is it as simple as matching up to the drill size required to make / match / final drill the hole?
Click to expand...

Hi Topturn.... Yes and No. As pointed out by Mark, use the 100 degree cutters for solid rivets and the #30 120 cutter for the pulled 1/8 inch rivet. Some cutters are labeled to match the number drill, but some are labeled to rivet size. So in my kit the #30 120 cutter countersink is labeled 1/2 X 120 X 1/8 so it is used for pulled CS 1/8 rivets.

Consider ordering cutters for screws also.

#40 3/32 rivet
#30 1/8 rivet
#28 #6 screw
#19 #8 screw
#10 #10 screw

I don't cut all at once. I used short bursts and watch for metal coming off, stop, insert a rivet and check for depth and so on and so on. For instance, after I primed the control horn and clecoed the control horn to the anti-servo rib, I needed one quick additional burst to remove the primer allowing me to seat the rivet fully. The rib acted as a backing plate so that the cutter could not wobble as I cut.

You WILL become skilled at removing both solid and pulled rivets which allows you recover from user error :)

Have fun,
Jeff
 
Add me to the list

All goes well until the dreaded CS4-4s arrive and countersinking proceeds as before (NOT!) I understand that there is a larger rivet that will 'fill' the rogue hole - does anyone know the size designator for such a rivet (if it exists). Vans have told me that the 100deg cs is not a problem per se as the rivet will conform as it is pulled to the shape. 120deg cs bits are a recent tool I was told. However the larger dia rivet sounds good - does anyone out there have real knowledge of this?
John
 
I know this may be only an "It works for me" solution, but I find that hand-holding small parts is a good way to C/S. I place a fingertip on each side of the hole so that pressure is evenly spread as I press the C/S in. You can feel when it bottoms and there is little chance to rock the countersink, or to let it attempt to enlarge the hole with sideways pressure. I have never had a part try to spin out of my hand, but I suppose it is possible.

Bob
 
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