rivets – chisel or drill?

I have always used a drill of the same size as the rivet (1/8, 3/32 or whatever) but stopped drilling just short of the tail of the rivet so that I do not open up the holes in the skin. The head then snaps off with the application of the pin punch. I admit it takes accurate drilling to do this and you need to be drilling dead centre on the head.

Yes that’s exactly the way I do this also.

I recently made an aluminium coffee table which I rivetted the top to using 100 ( 😮 ) rivets. Was hard-going using a hand rivet-gun !!!

Here’s a (not so clear) picture if you’re interested.

TNZ

The dimple in the head of US rivets is to aid rivet removal and has been a feature of them for years. I always use a pin punch for rivet removal once the head has been drilled to the depth of the top of the skin on a mushroom rivet and on a countersink just to the depth of the countersink. A pin punch is by far the best tool for removal and leaves no lasting damage.
In the case of Cherry rivets I would advocate filling gently on the rivet head to loosen the locking collar and then punch the mandrel out. The same procedure can be used as a solid rivet.

I have always used a drill of the same size as the rivet (1/8, 3/32 or whatever) but stopped drilling just short of the tail of the rivet so that I do not open up the holes in the skin. The head then snaps off with the application of the pin punch. I admit it takes accurate drilling to do this and you need to be drilling dead centre on the head.

For both dome and c/sunk, I centre-punch with one of those spring-loaded punches, then drill to just below head height with a drill just very slightly narrower that the shank. Then I use the shank of another same size bit to “worry” the head off.

Then punch out the tail.

Time consuming, but does not damage the skins.

KM

In my own experience (reskinning C-130 flaps for Marshalls for 18 months) we usually found that chiselling dome head solid rivets would only work if the heads had already been weakened by drilling. As we were on piecework (bonus payment for job done quickly) the ‘old hands’ would just arm themselves with a heap of new drill bits, then drill into the rivet heads until reaching the point where the underside of the head would be. Then a quick flick of the wrist (so to speak) and the head would ping off onto the drill bit. One guy once tried air chiselling without predrilling but it took longer and made one one awful racket.

I use a parallel pin punch to remove SP85 or SP80 rivet heads instead of the drill (or chisel) as the heads stack up on your drill bit like a kebab and are a pain to remove!

In my own (limited) experience I have used a chisel to remove hinges from panels by knocking off the rivets. Since the hinges were scrap anyway this was the quickest way, did cost me a (home made) chisel though! Drilling off the head as explained above is still the best way I think.

In my own experience (reskinning C-130 flaps for Marshalls for 18 months) we usually found that chiselling dome head solid rivets would only work if the heads had already been weakened by drilling. As we were on piecework (bonus payment for job done quickly) the ‘old hands’ would just arm themselves with a heap of new drill bits, then drill into the rivet heads until reaching the point where the underside of the head would be. Then a quick flick of the wrist (so to speak) and the head would ping off onto the drill bit. One guy once tried air chiselling without predrilling but it took longer and made one one awful racket.

Then go on to the next one and so on until you have a drill bit with about 20 rivet heads on it. Put in a new bit and start again. Takes practice but very efficient once you get going, and also saves damage to the skin, which you can then use as a pattern without any wobbly holes. The same method will work for countersunk rivets, just be a bit careful if you want to re-use the skin. Practice with a bit of old unwanted structure is always worthwhile. Air drills are the best because of higher speed and better controllability.

As John C says, blind rivets need more care – if you loosen them they will spin and rip the holes to bits – which as blind rivets tend to be used in thin structures is not to be desired when you’re trying to restore something rather than make it worse…

Having said all this, I have used a chisel, my favourite was an old ‘un picked up at a boot sale I think, and ground to a smooth curve on one side to give a bit of protection to the skins. Used to work a treat!

Sounds like Cherry rivets to me – they were widely used on US designs as they are the same idea as pop rivets, but a lot stronger (and also about a quid a throw these days). Where a pop rivet has a hole in the top, the Cherry type leaves the mandrel more or less flush to the top of the rivet.

Sound about right?

JC

uhm

photo(s), please ?

TIA
Martin

Identifying aircraft type from the rivet!

All

Here’s a poser…!

Several years ago, I was walking along the beach at Thorpness, Suffolk. Found a piece of aircraft washed up, that was still good aluminium on one end, with greased bolts and paint visible, and corroded to powder at the other end! The clean end must have been buried. I have never been able to identify the aircraft type, but I have been informed that the centre-popped mush-head rivets used are US wartime. The leading edge is steel, with a pointed nose. It looks like the elevator of a fighter, because of it’s dimensions. I have had a good look at as many wartime US aircraft as possible, without any luck.

Excellent, that clears it up. Now, does anyone have a fuselage I can practice on? Have own drill, and can swear to required hangar standards.

Andy A.

Agreed Mark, although a lot of the rivets on the wing I was working on recently had a centre mark on them (from the forming tool) so that wasn’t a problem. Having said that, the last lot I took out didn’t. And they were on the underside of the wing. And they were all different sizes. That was fun.

JC

I agree with John C, one thing to add though – file a flat on dome head rivets then centre punch it to provide an accurate ‘key’ for the drill.

In my very recent experience…

1: Solid Rivets. The approved way is to drill the centre of the rivet down for about 3mm (or the depth of the rivet head plus a gnats) and then chisel the head off. The drill diameter should be very slightly less than the rivet shank. If you get it right, the rivet head will chisel off very easily. If it doesn’t you haven’t drilled down enough or used a big enough drill. The advantage of doing it this way is that just chiselling will buckle and stretch the panel and just drilling risks enlarging the hole.

If one drills all the rivets first (air drill is best) and then sets the chisel along the line of the rivets, one hammer strike is likely to knock 5 or 6 rivet heads off at once! Sad but satisfying 🙂

2: Cherry (or blind) rivets. As above, but first the rivet head needs to be ground back and the mandrel punched out. If the mandrel doesn’t punch out easily grind it back more. The drilling and chiselling bit is easier though!

The important thing is to ensure that the panels do not take any damage if at all possible (although this is sometimes unavoidable) as all you’re doing is making more work for later!

The above should work for the majority of domed rivets. Flush rivets need a slightly bigger drill and no chiselling. And remember that there’ll always be one that resists all efforts to remove!

JC
Oh and what they all said before is right as well 🙂 Especially the swearing bit.

Oh and be prepared to swear a lot.

I forgot to add that to my post. Thanks for reminding me Steve 😀 😀

Drilling rivets

When removing a panel from an aircraft, there seem to be two methods of getting the rivets out – chisel off the heads or drill through them. I have heard several people say one way is better than the other because it does less damage. Drilling off the rivet can potentially make the hole larger, but chiselling can damage the panel. Should one method always be used over the other, or does it depend on the circumstances? This is not something I’ve done before; I’m just intrigued to see what the experts out there think!

Andy A.

If you are drilling out Mushroom headed rivets, it is best practice to drill the centre of the head of the rivet and carefully chisel off the head and punch out the tail. It takes time and care, and if done properly you won’t damage the skin. As for countersunk rivets, drill the centre of the head to just below the depth of the countersink depth and punch out the tail. With both types of rivets have someone behind the ofending rivet with a block otherwise you will end up with a mashed in skin and stringer or whatever you are removing it from.
Hope all this is helpfull.
Ta Ta.

Forgot to say, on mush heads, try and file a flat on the head so you can drill without skidding off and knackering the skin

I’d second everything Galdri’s said. I’m also no engineer, but have had a go on rivets and they’re quite tricky and time consuming. Chiselling? Only if you don’t want to use the panel again! 😀

I was always told to drill them. If anything, use a smaller drill bit than you think you’ll need. Take it very slowly and one of two things will happen; either the head of the rivet will gently come off onto the drill bit, or you’ll need to up the drill size a bit and try again. If the rivets are domed heads you might need to use a punch to put a pilot hole on top so the drill stays where you want it to.

Oh and be prepared to swear a lot.

I’m certainly no expert, not having any qulification as an engineer, but I’ve drilled a few rivets! The trick is to drill very, very carefully. There also a lot of practice involved. If you are in practice and have the correct size drill, you will not damage anything.

As for chiselling, I’ve never even heard of it for removing rivets.