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Bad countersink

LAMPSguy

LAMPSguy

Well Known Member
Today I started some countersinking and almost immediately I noticed them coming out over size. Long story short, the cage was not moving, but the shaft inside it was out of round by .005 (confirmed with dial indicator and slowly rotating it). This runout made the bit itself move in an orbital motion and enlarge the hole (the cutting surface goes a bit too far down the guide for my taste, I have a photo below to describe the fix. I figured it out pretty quickly and switched to a better CS cage and finished up the work I had to do today.

So, I have a few holes on the outboard edge of my spar (last 5 rows maybe) that are just a touch too big all the way to alot too big. Please tell me the spar is not done and I just fill it with the rivet and it will squeeze into the void and be fine!

In the photo below, you can see the -3 rivet in a fresh hole with the worst hole directly beneath it. It is not quite the size of a -4 rivet, and it has not been CS too deep, just widened a bit.
12360k6.jpg



In the next photo the rivet is inserted from beneath so you can see how bad it ended up. These are the holes that will take the skin dimples.
73dsh2.jpg


My thoughts are:
a)Drill it one larger to accept a -4 rivet (the CS should be fine for the skin dimple
b)Keep it and just us a a 0.5 longer rivet to fill the space
c)Something else I haven't thought of?

The picture above is the worst, there are maybe 5 total with the rest being less extreme as this picture. Additionally, they are the most outboard part of the wing if that matters. I plan to call Vans next week, but thought I would start here.

Additionally, there were a few others on the other wing where the CS ended up a little deep/ They are more deep by a few thousandths than the others, noticeably so, but there is still just a little bit of metal left to hold the rivet...it is not a knife edge I mean. The middle hole shows the amount of remaining metal underneath the CS...maybe .008" I am guessing.
sgsb50.jpg
 
First off, my guess is that you are using a high speed air drill. If so I suggest you change to a slower turning battery drill. Even with run out on the C.S. cage, you probably wouldn't have done this if it was turned slower.

The holes that are only very slightly over size should be ok with the standard rivets. Any others I would us NAS1097-4's, as long as it isn't a bunch and tehy are not grouped tightly together.
 
I would not try to fill the hole with a standard rivet. I would use an oversize shank rivet "ooops rivet", which can be had from Vans or ACS here http://www.vansaircraft.com/cgi-bin/store.cgi?ident=1367111516-304-582&browse=hardware&product=oops

These rivets have an 1/8" (-4) shank but have a -3 head. Alternatively, you could drill out to the next size and use a -4 rivet. The only difference being the cosmetics. As suggested in the previous post, use a slow turning battery drill to do all your countersinking. You will get a much cleaner cut and no chattering at the slower speed.
 
Always, Always test everything on scrap first! If you don’t have any, get some! It will save you huge $ in the end!!

As a builder the hardest lesson I had to learn was – SLOW DOWN and CHECK IT, CHECK IT and CHECK IT AGAIN! It's not going to fly tomorrow so, SLOW DOWN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

One other thing.. when countersinking multi-holes, about every 8 I test with a rivet (Same with the Squeezer) and I ALWAYS test the 1st two. I think you will find that the scrap and the actual work is always a “Click” or two off.
 
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Rivet Checks...

randyintejas said:
One other thing.. when countersinking multi-holes, about every 8 I test with a rivet (Same with the Squeezer) and I ALWAYS test the 1st two. I think you will find that the scrap and the actual work is always a ?Click? or two off.
Click to expand...

When countersinking, I always grab a long rivet (like a 3-5 or 3-6). I keep it between my lips to have hands free and then I check every countersink as I go. Also, I think it's important to have a sharp CS bit if you're using a high RPM air drill. The last little trick (for skins) is to back it up with a piece of scrap with a hole drilled in it. It doesn't have to be large, but this can help with warbling if you have to make a CS hole that's a little deeper than usual (like when it receives a dimple). My $0.02.
 
help; how do i post

for some reason I cannot find where on here to make a new post. I thought there was a place that said new post or new thread; but for the life of me I cannot find it. can anyone tell me where to go . thanks Bruce
 
LAMPSguy

That must have been a very bad quality CS cutter - Does it have a bush or a proper bearing for the shaft ?
 
What Mike said. A small backing plate made from thick scrap with a hole the same size as the pilot on the countersink will help even if there's a little wobble. Works especially well on material that's on the thin size of acceptable. Just clamp it tight so it doesn't wobble too.
 
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Bruce, open the forum you plan on posting on like RV-14, RV General Discussion/News, etc. and at the top of that page you will see "new thread", I do believe.
 
Cage

The funny thing is that I have 2 cages, from the same tool dealer, ordered at the same time, same model, and the "heavy duty" USA made version rated to 10,000 RPM. The bad one has noticeable roughness when turned. I tried to take it apart but could not for the life of me get the bearings out.

I used an electric for the other side of the spars today and it worked very well...but after doing both spars on both sides, the cutter was noticeably more dull, can they be sharpened or just toss and buy a new one?

Before I CS the rest, I match drilled a backing plate just in case VANS says to do that for the side where I CS'd a little too deep. Email sent, we will see what they say.
 
LAMPSguy said:
...but after doing both spars on both sides, the cutter was noticeably more dull, can they be sharpened or just toss and buy a new one?
Click to expand...

The anodize coating is very hard and hard on cutting tools (dulls them quickly), and running it at high speed probably makes it worse.

Just get a new cutter. It should stay sharp for the rest of the project (no more anodizing).
 
Talked to VAN's

Word from Vans was this:

For the oblong holes, since they are so far out on the wing, just use an OOps rivet. For those who have never used them (me) just drill out the hole to -4. Dimple the skins like normal for a -3, THEN drill the specific dimpled holes to a -4.

For the 5 pairs of extra deep countersinks, just move forward and fuhgettaboudit. There is still some metal to support the rivet shank and it is so far out on the wing (glad I started at the tip vice root!) that it should be a non event.
 
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