Little help with riveting

rjcthree · #1 11-06-2007, 05:55 PM

Hi, I'm riveting rear ribs to the main spar on my -9, (426-4-7) and getting a lot of edge 'smiles', I'm assuming due to gun bounce. MFG head to the rib, per instructions, requiring me to use a offset set on the gun. Any more pressure/volume, or for that matter, any less, and it gets worse. Tungsten bucking bar. About 1/3 of them now have marks that are best described in section 5 of the manual as 'ok but ugly'.

3x US Industrial gun. 60 psi, throttled about 1/3 open.

Any ideas?

Rick 90432

jsharkey · #2 11-06-2007, 06:24 PM

Keep the rivet set as square to the rivet head as possible.
Once the rivet is set keep pressure on the gun until well after you release the trigger.
Releasing pressure before stopping the gun means that there is a chance of a random strike from the gun and that can cause "smiley" rivets.
You might need a third or fourth hand - one to hold the bucking bar and one to stop the offset set from rotating and bouncing off the rivet head.
Just some ideas of what might be happening!

Transporter · #3 11-06-2007, 06:56 PM

Some guys use a small piece of duct tape on the face of the rivet set to minimize smileys; I just tried a product called "Snap-Soc" from Brown Tool and they work well for me-the plastic cap helps keep the rivet set centered on the rivet head. They come ten to a pack and are sized to fit various rivet sets.

http://www.browntool.com/productsele...?productid=659

Regards,
Mike

LettersFromFlyoverCountry · #4 11-06-2007, 07:28 PM

Yeah, offsets are a pain in the neck. Make sure you're letting your bucking bar do the work, too. There's a tendency to put a lot of pushback pressure on bucking bars and if that's done...the bar doesn't get the energy to do its job. (on Dan Checkoway's site, there's a really good explanation of this, using those balls where you let one end go and hits the row of balls and only the end ball moves).

Anyway, the suggestion to get some help is a good one. Get someone to handle the bucking bar, freeing a couple of fingers on your free hand up to hold it to the rivet.

If you're getting all sorts of marks on your manufactured head, your rivet set is, basically, acting as a bucking bar on it. You just need to control it better either by turning the pressure down, using a free hand to hold it on the rivet...or -- preferably -- a combination of the two.

Mel · #5 11-06-2007, 07:29 PM

Try using a different rivet set. I have one set that will "smiley" no matter what. I've looked at the set with a 10X loupe and can't see anything wrong, but I just can't make it work. All my other sets work great.

Rick S. · #6 11-06-2007, 07:38 PM

Good ol' 426 rivets. They were the hardests to train myself on because they are intolerant of bounce and rivet sets that are not perpendicular to the surface. Although I still use masking tape over the head for peace of mind it really boils down to technique, proper gun placment and proper pressure (psi) to the gun. FWIW Dan Checkoway has a rivet gun pressure guide for riveting on his site that I found right on for getting started. But!!

Masking tape on the rivet head works wonders to improve your technique.

RScott · #7 11-06-2007, 08:45 PM

60 psi is too high and those regulators that mount on the gun just regulate air flow, not starting pressure, so your first blow hits with the full 60 psi. As you continue to rivet with restricted airflow, the pressure drops, and it may actually drop so low within the gun that it won't drive a 426AD4 rivet.

Dan Checkoway shows 50 as the highest pressure for 426's and 80 for 470's, and in my humble opinion 50 is too high & 80 is way too high. I rarely go much over 40, but small or excessively long air lines may require his 50 psi to maintain gun pressure. SynergyAir teaches that 40 is all you ever need.

Tony Bingelis wrote in Sport Aviation, "The proper pressure at the gun is a far lower pressure than that most builders assume to be essential. Would you believe a mere 25 psi is all you need for 3/32" rivets, and a slightly higher, 40 psi, for 1/8" rivets?" See his article at http://dad.walterfamily.org/rv/TonyB...ng%20Tips.html

My suggestion is to: 1. Throw away the gun mounted regulator, 2. Drop down to 40-45 PSI, and 3. Hold the rivet set with one hand while someone else holds the bar. If you do 1 & 2, you may not need the helper.

Richard Scott
RV-9A Fuselage

az_gila · #8 11-06-2007, 08:47 PM

Quote:

Originally Posted by Mel

Try using a different rivet set. I have one set that will "smiley" no matter what. I've looked at the set with a 10X loupe and can't see anything wrong, but I just can't make it work. All my other sets work great.

Like Mel... I found one set I had was machined a bit "deep", and was absolutely not tolerant of any lack of perpendicularity. It marred almost 100% of the time

Really cheap sets may have sharper edges and will mar much easier. A ScotchBrite polish may help on these.

Try borrowing some other sets from other builders and see if it your set, rather than the technique.

I try and operate my rivet gun with the throttle near full open... perhaps with your 1/3 open the first hit is too hard (full pressure and no flow yet) and makes your set jump a bit?

Let us know what works for you... gil A

Captain Avgas · #9 11-07-2007, 03:17 AM

Quote:

Originally Posted by rjcthree

Hi, I'm riveting rear ribs to the main spar on my -9, (426-4-7) and getting a lot of edge 'smiles', I'm assuming due to gun bounce. MFG head to the rib, per instructions, requiring me to use a offset set on the gun. Any more pressure/volume, or for that matter, any less, and it gets worse. Tungsten bucking bar. About 1/3 of them now have marks that are best described in section 5 of the manual as 'ok but ugly'.

3x US Industrial gun. 60 psi, throttled about 1/3 open.

Any ideas?

Rick 90432

Firstly, are you trying to drive these rivets on your own. If so, get a partner before you do more serious damage...like dinging the reinforcing bars on the main spar.

rjcthree · #10 11-07-2007, 05:37 AM

Guys, thanks fpr the help.

Experience has shown me that:

regulated and buffered (header tank) 25psi full-open throttle sets -3's nicely.

Previously 40 psi full-open throttle drove 426-4's nicely when I could get at them quarely.

I don't make smiles on the first hits - it's at the tail end of the set - like I'm losing control of the gun.

My rivet sets may suck - it was the kit from A/S US Industrial to start - it was cheap - funny how I replaced much of it. I keep learning that lesson . . .

Who's rivet sets are best? Avery? Cleaveland? I like Avery's stuff . . .

I'll be moving my regulated/header tank device to the back shop and removing my throttle from the gun next, along with masking tape, just to see . . .

Rick 90432