Drilling out countersunk rivets

rv6builder48138 · #1 03-15-2006, 07:51 PM

I've had a **** of a lot of practice at drilling out rivets. However, until recently I've had problems drilling out countersunk rivets. I couldn't get the hang of drilling into the rivet head to the "right" depth; I'd either drill too shallow (and be unable to snap the head off with a punch) or drill too deep (and thereby enlarge the hole the rivet was in, unless I was dead-perfect in centering the drill on the rivet head).

The answer to getting the depth correct:

1) lightly centerpunch the rivet head (especially if the little center "dimple" in the head was shallowed or flattened when the rivet was driven).

2) put a drill stop on the drill bit you'll be using to drill out the rivet. Set it shallow enough that you are sure you won't be drilling too deep, and carefully drill a hole, using the dimple you enlarged to center the drill, till the stop touches the rivet. Try to snap the head off (don't try too hard). If the hole isn't deep enough, loosen up the drill stop just enough to allow you to just barely move it (enough to deepen the hole just a hair). Run the drill into the hole again until the stop again touches the rivet head. Try to snap the head off. Repeat until the drill stop is at the exact place on the drill bit to consistently drill the right depth hole and easily snap the rivet head off. You might have to then drill a smaller-diameter hole in the middle of the remaining rivet shank to loosen the shank up a bit and allow you to pull or punch it out.

Set the assembled drill bit/drill stop aside for future use. I know, I should be an optimist and have enough faith in my riveting skills that I don't have to drill out any more rivets, but I'm only 2/3 of the way thru the wing kit...I just KNOW I'll have more opportunities

to use that drill stop.

jdmunzell · #2 03-16-2006, 07:48 PM

That is a very handy technique. Did you figure this method out yourself or did you read that somewhere "official like"? Doing my wing skins is just around the corner for me, so this is very handy information indeed!

What a great resource this place is! Thanks for submitting your solution to a common problem.

Jeff
-8 wings

RScott · #3 03-16-2006, 08:34 PM

Having enlarged too many holes, I have learned the hard way, "don't drill out no stinkin rivets" unless you really have to. As Van's says, you could build the plane with only every other rivet & it would still be safe, so if you have one now & then that isn't up to par, don't worry about it.

kevinh · #4 03-16-2006, 09:31 PM

Another common trick: Use a #42 bit, not #40. It more tightly fits around the punch, substantially increasing the odds of a clean break when you pop off the head. The hole also doesn't need to be as deep...

I guess it also provides a little margin if you drill to far.

rv6builder48138 · #5 03-17-2006, 04:42 AM

I finally lit on the idea after drilling out many, many rivets. I don't know what came over me lol. I know you can have some pretty bad-looking rivets and still have a good-flying airplane, but in my case, those rivets were awful!

In my case, I had to drill out a ton of rivets for the LE assembly of my right wing and take the assembly completely apart to replace the skin. I didn't realize that I'd cut the hole for the Duckworks landing light in the WRONG end of the assembly until it was too late. Sheesh.

Doug R., maybe we need a category for "most embarassing oops." Mine would be a leading candidate for the gold medal, or at least the silver.

Using the smaller drill bit is a good idea, too, I'll have to give that a try. John

RV7ator · #6 03-17-2006, 06:40 AM

Perfect application for "oops" rivets. Drill out the ruined hole to 1/8". If the hole is slightly oversized, presqueeze a standard rivet to fill and it will buck/squeeze without tipping (provided you don't screw up again).

It's real easy to see if the drill point is centered, and remains so, simply by looking, bullseye-like. Centerpunching helps get it started...ah...centered. You can walk the drill if it drifts off by tipping it back towards center. Can't do that with a drill stop in the way, and sooner or later you're going to need a 12" drill to reach a deep rivet. Guaranteed: there's a 1/8 -8 in your future that will need drilling. Where you can't see it directly. Hidden. Not a straight shot and too cramped for a bit/motor/hand, and up against an obstruction that bars using a stop.

Where a drill stop shines is instances where you're really leaning on the motor, say when drilling the zillion fuse longeron holes. The stop keeps you from plunging through and invariably the articulation of your arm will tip the bit, elongating the hole.

John Siebold

rzbill · #7 03-17-2006, 10:38 AM

I think I have been fairly successful at removing rivets. Here's what I do.

On all rivets, 426 or 470, I use an automatic center punch to enlarge the center dimple.

At very reduced speed, I drill with a 1/32" undersized bit (#40 for 1/8 rivets, 1/16 for 3/32 rivets) well into the body of the rivet. Here is the trick. Stop early and check the centering of the new hole on the rivet head. Watch out for the bit "walking" one way or the other. If it is, angle the drill to move the hole back towards the center. Get this all DONE before passing the head thickness. This is easy and gets to be second nature.

Next I drill with the rivet body size (#30 or #40) down to the skin (it will follow the small hole) and use the back side of a spare body drill (because it fits tight in the hole) as the "punch" to peel off the head.

Afterwards, the remaining rivet shank will fall out or come out with a one or two pushes with the automatic center punch.

The hole is left as pristine as it was before the buggered up rivet occured.

The most proud application of rivet drilling for me was on the steel pushrods. I did have a b*tch of a time setting the rivets square in the small steel pushrods, so I wound up drilling out most of them. All without touching the drilled hole edges at all. Because the rivets are over 1/2" long, I had to drill most of the way through them to get them to release.

I'm well into the fuselage and I have use 2 oops rivets so far on the whole plane, and one was a bad drilled hole in the first place.

With practice, rivet drilling has become very easy for me. Easy to the point of replacing rivets for cosmetics only.