Breaking SS rivets ? air pressure too high?

[David H]

I’m using an older air powered rivet like this one:
Unknown.jpeg

on the SS rivets for the ribs during my wing build. It has served me well for years. I am using the 12 degree angle tool I made per Mitch’s instructions. Most pulled just fine, but several of the mandrels broke at various places. Some close to the rivet head, some near the end of the mandrel that goes in to the rivet gun. The gun really fires off hard at 90 psi.
My gage built cherry max rivet guns pulls more slowly and smoothly at 90psi.
Should I just regulate the air pressure sown to ?40psi or...???
SS rivets do drill out, but when the mandrel breaks off with 1-2 mm exposed, not much fun to have to grind off mandrel then drill out.
Thanks guys,
David

[DRL]

I’m using an older air powered rivet like this one:
Unknown.jpeg

on the SS rivets for the ribs during my wing build. It has served me well for years. I am using the 12 degree angle tool I made per Mitch’s instructions. Most pulled just fine, but several of the mandrels broke at various places. Some close to the rivet head, some near the end of the mandrel that goes in to the rivet gun. The gun really fires off hard at 90 psi.
My gage built cherry max rivet guns pulls more slowly and smoothly at 90psi.
Should I just regulate the air pressure sown to ?40psi or...???
SS rivets do drill out, but when the mandrel breaks off with 1-2 mm exposed, not much fun to have to grind off mandrel then drill out.
Thanks guys,
David

Reducing the air pressure to the minimum necessary to pull it properly and without jumping off the material will certainly help. If the gun comes off while pulling, it may break prematurely. Another problem can be a stem that did not eject properly and is still hung up in the gun or the jaws not gripping the mandrel correctly. It is wise to first practice on a spare piece of material to get the pressure right.

Anything can be drilled out, but an SS stem must be knocked out first, before the rivet can be drilled, not easy. The problem is hitting the stem hard enough to knock it through without damaging the surrounding structure. The sharp tap required can cause all sort of problems if not done right. Grinding the head first will help, but has its risks.

[Daveembry]

Reducing the air pressure to the minimum necessary to pull it properly and without jumping off the material will certainly help. If the gun comes off while pulling, it may break prematurely. Another problem can be a stem that did not eject properly and is still hung up in the gun or the jaws not gripping the mandrel correctly. It is wise to first practice on a spare piece of material to get the pressure right.

Anything can be drilled out, but an SS stem must be knocked out first, before the rivet can be drilled, not easy. The problem is hitting the stem hard enough to knock it through without damaging the surrounding structure. The sharp tap required can cause all sort of problems if not done right. Grinding the head first will help, but has its risks.

http://products.afi.cc/contentonly.a...endors/POP.pdf

Looks like 4 conditions which may also be the reason for a "high mandrel break" in the troubleshooting guide.

[David H]

OK. Fixed my problem. I reduced the pressure going in to the rivet gun. 40-42PSI indicated works perfectly. Also, if I bend the mandrel more than needed to be perpendicular to the face of the rivet puling shim (>12 degrees) they were breaking frequently.
IMG_4008.jpgIMG_4009.jpg

[David H]

Ok. Here was my final solution. This worked beautifully. Once I got the pressure dialed in (42PSI indicated) I never broke another mandrel with my air powered puller on the remainder of L wing and all of R wing.
IMG_4069 (1).jpg



The coiled pneumatic hose came from amazon:

https://www.amazon.com/Coilhose-Pneu...72PH5S7XY5N2NK

Super high quality, USA made. I got the 50’ length to give me a little more maneuverability. The 50’ is the fully stretched out length.

The regulator:

https://www.amazon.com/Bostitch-BTFP...ed+air+regulor

I’m also using this for my air drill, air angle grinder. Is fantastic. Highly recommended:

http://www.cleavelandtool.com/Lightw.../#.V90tuzuMP68


Hope this helps.

David