Newbie: Acceptable Riveting?

[fergusnoble]

Hi all,

I'm just getting started building my Sonex tail kit and am getting a bit hung up on what constitutes an acceptable rivet installation. I've noticed some variability and while I'm sure most of it is normal I'd like to get a better picture what I should replace vs what is expected variation. FWIW I'm using a standard Harbor Freight pneumatic rivet gun.

1) The first thing I noticed is that on the blind side of the rivet, sometimes the stem is pulled deep into the rivet and sometimes it stays closer to the top. In both cases it seems as though it has set correctly but I'm not totally sure how to judge this.



2) Almost always the stem breaks far down in the rivet but occasionally it will break higher up so you can see the stem from the rivet head (but still below the surface). The back of the rivet looks fine and it doesn't seem to correlate with (1).

I have modified one of the tips of the rivet gun by grinding it to an angle such that I can pull rivets in tight areas. The steam breaking higher seems to happen more frequently with this mod. With the mod I also had one stem break slightly proud of the head, again the rivet looks otherwise fine.

Any other tips on rivet quality control?

Thanks to everyone in the community here - this has been a fantastic resource getting started on my Sonex!

Fergus

[Bryan Cotton]

Fergus,
I almost never look at the back side of the rivet. There is some variability on how they pull no matter what puller you use. Mine are also HF and I have a couple old American hand pop tools. On the backside you do want to ensure the rivet has been swelled into the metal you are riveting and everything has pulled tight. On the factory head side you want to make sure the head is tight against the parts. When you rivet, like when you drill, the key thing is to keep it perpendicular. Also there are a small amount of bad rivets, get in the habit of taking a quick look before you set them!

I have not had any mandrels break proud. If I did I would take my right angle sander to them. Also, I hope you still have a straight head to set straight rivets. Look at the Sonex video tips for riveting with a wedge for corners.

I put a 12 (now 14) year old in charge of rivets. It is that easy.

[GordonTurner]

Hi Bryan

How come he was 12 and now he's 14? I seem to be having the same problem here. They were 14 and 15, now they're 16 and 17. Where is this trend leading?

Gordon

[Rynoth]

You want to pull at a lower psi setting on your compressor than you'd use for drilling or other tools. I'm generally around 40-45psi. What I look for is a relatively slow pull of the rivet that still pops it in 1 trigger action of the rivet gun. Slower pull controlls the work hardening of the ss right before it sets.

[Area 51%]

Tried many different pressure settings to get a repeatable rivet set. It seems it was either too high, causing a quick pull that didn't allow the rivet head a chance to lay flat if it weren't perfect to start with, or so low the mandrel wouldn't break.
For me, the answer was not in the pressure, so much, but the volume of air going into the gun. At first I tried to reduce the flow by closing the valve at the compressor to a trickle. Probably would have worked if there was only .5 inches of hose between the valve and gun. Instead, I have a 50ft run of piping between the compressor and workshop, and no matter how fast I loaded the gun with another rivet, the pipe acted like a 3/4in diameter by 50ft long air tank that happily filled to tank pressure between pulls.
What was needed was a restrictor to limit air-flow into the gun. I tried a valve inside the workshop.......same results. Tried pinching the hose.......couldn't get the restriction close enough to the gun to be effective and still have enough flexibility to work with. Tried a flow restrictor at the base of the gun.......too bulky to use, but did confirm my belief in volume control.
My solution ended up being almost comically simple. While fishing around in the bucket for a rivet, I encountered one that had no mandrel. It was one of those moments when you look at one hand, then the other, then back again. I uncoupled the quick-disconnect, then put the mandrelless rivet into the male portion of the disconnect attached to the gun, then reattached the hose. The result was sublime if not perfect. The restriction slowed the pulling process regardless of the pressure. I did need to remove the rivet and flatten the end slightly to slow the process further, but after 3 tries, I had what I needed.
I had been getting about 1-in-50 rivets setting crooked. Now the only ones that aren't flat are the "culls" that made it past Textron's quality control.....and mine. Another benefit is that the recoil has been all but eliminated.
An important note.....you WILL forget it's in there, and when you disconnect the hose, it Will run and hide in some crack on the floor. It probably goes where the missing socks go. The good news is, I have over 5000 restrictors.
Happy thoughts from Area 51%

[rizzz]

You want the lowest pressure possible.

It is also a good thing if the stem does not break in 1 pull, more pulls is better. I had mine usually set to break in 2-3 pulls, that way you know for sure the pressure is as low as it can be (any lower and I could not get the stem to break at all in no matter how many pulls).

Experiment to try and find what that pressure setting is, on my setup it was 35-40 PSI depending on rivet size.

Unlike with solid rivets, with pulled rivets you cannot be too judgmental about what the shop end looks like after pulling the rivet.
They will all look slightly different.

[DCASonex]

Been trying to tell folks that for years. Thanks for the confirmation. A simple adjustable resrictor (sometimes called flow control or incorrectly - a flow regulator) which can often be found with integral 90 degree swivel works great. If left screwed into the rivet puller, you can leave your pressure regulator set at 70 - 80 PSI and switch to an air drill without adjusting pressure. The actual force on the rivet mandrel will not be any higher than with low pressure, nor will the "thump" that occurs as the mandrel breaks and piston travels full stroke, as the pressure in the puller's large piston will build slowly.

While about it, trim the length of the trigger on the puller so that just two fingers grip it, other two fingers then can better hold the puller. By holding the puller lightly, and setting restrictor for about 1 to 1-1/2 second per pull, you can feel the puller try to self align with the rivet head and that feedback results in very accurately aligned rivets.

David A.