Back riveting AN4 rivets

[Nova RV]

I have been having a problem back riveting AN4 rivets, they are almost always about a thousandth or so proud of the dimple when set. Never any issues with the AN3 rivets. I have double checked the #30 dimples, and they are fine and the rivets are flush before setting, I have tried more "mass" by adding a tungsten bucking bar on top of the back rivet plate but this is tricky to not get it to fall off and dent the skin but does help some. I even tried the back riveting plate (from Avery) on a concrete floor and still got a rivet that was slightly proud of the dimple. I tried lowering the pressure to about 40psi and held it on longer but I am worried I will work harden the rivet by hitting it too long. So far this is more cosmetic than anything but I really would like to figure this out. Open to suggestions... thanks

Avery back rivet plate
Cleaveland back riveting set
3X rivet gun

[rv9builder]

Try putting a piece of tape over the head of the rivet to hold it in place, then back rivet the normal way.

[Nova RV]

I have been using blue painter's tape and thought maybe the thickness of the tape was the issue and tried Scotch tape but no luck... and if I use a rivet gun and bucking bar and just rivet normally it's all fine.

[BobTurner]

Sounds to me as if the spring loaded collar around the back-rivet set is not pushing the work piece down hard enough.

[John Tierney]

You don't mention what surface the back rivet plate is on or the air pressure setting. If the plate is set on a table or bench that has any flex you may be getting a little bounce during the initial setting of the rivet that causes it to sit high. Also, make sure the pressure is higher for the AN4 rivets, particularly with a back rivet set or any long sets, as some of the gun energy is lost travelling the length of the steel set.

[rv9builder]

Hmm...if the tape trick isn't working, I agree with Bob--make sure the spring-loaded plastic collar around the set is pushing tightly against the skin.

[Mudfly]

I think the use of painters rape as a v9builder describes is meant to act rwo purposes. It holds the rivet in place,and also acts as kind of a spacer to allow (possibly) a small amount of concentrated force on the rivet head. I don't know if it works, but I have had the same thought process.
Also, you might try, where space allows, to use a straight rivet set instead of the one with the plastic collar and spring. Just use your fingers (as close to rivet shank as possible) to hold pressure on the pieces being riveted together. In some cases, I think you may be able to hold more pressure than the spring-loaded rivet set can apply, which in turn should hold the manufafactured head more flush.

[Nova RV]

I'm running about 40-50 psi on the back rivet set with the AN4 rivets. I try to judge pressure by how long a burst is needed to set the rivet. I'm riveting on a wood work bench with 3/4" top and have tried adding layers to the top with more 3/4 ply but the kicker was trying it on the concrete floor and still getting this odd set. I have tried a std Cleaveland back rivet set as well as their longer one and a generic back rivet set as well all with same results. When I set the rivet I'm leaning on the gun pretty hard to keep pressure on the parts but still get the impression they are somehow bouncing causing the proud set. I will try a straight set tomorrow and see what happens.

[leok]

The rivet manufactured head sits a little high when the rivet is set while the material is not fully seated, i.e. the rivet is not tight to the material.

It can happen if the dimple process pulls a little convexity into the surrounding material, or the back-set collar is not pushing down hard enough, or again if the material is flexed over the back rivet plate. When I have seen that result, I drill the rivet out, then pushing down on the collar with my free hand. I drive the rivet. So far, it always pulls the head in tight.

I also drive #40 and #30 rivets with the same gun pressure. A 1 second burst for #40 and a 2 second burst for #30. Unless it's one of those long rivets, then the gun gets more pressure (sometimes a lot more) Again, so far, no issue with hardening.

[BobTurner]

Originally Posted by leok

then pushing down on the collar with my free hand. I drive the rivet. So far, it always pulls the head in tight.
g.

+1. You need to push down on the collar, not on the gun.