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Questionable Rivet

AboveMSL

AboveMSL

Well Known Member
Hello Folks,

Had the bucking bar slip a bit resulting in an uneven shop head. Wondering if I should leave it alone, replace it, or try pounding it a bit more. The rivet attaches the HS405 to the HS710 and HS702.

Also, I am terribly unsuccessful at drilling out rivets, despite a great deal of practice on scrap parts. So I would only like to do this as a last resort. (Which I guess is always the case anyway) :rolleyes:

This is my first post and I'm not sure how to attach a picture, so here's a link to it on my mobileMe site.

http://gallery.me.com/tilf#100203

Thanks,
Greg
 
Hi Greg,
Is that your finished rivet? It looks a bit underset, but it could just be the picture. Mel is right, though, build on! If you have an ugly rivet every once in awhile, it's no big deal.

Search the forums because awhile back someone did a pull test on varying rivets...overset, underset, and normal, I think. I don't recall exactly, but the overset and underset weren't that much weaker than a normally set rivet. Obviously, you still want to do it right, but don't let the occasional "bad rivet" bother you.

Edit: Mel, you're not getting squeemish about posting advice are you? You deleted your post pretty fast!
 
First, I'd agree it looks a little underset. Second, think what you are trying to achive. The strength of the rivet is in shear, not tension. If you have filled the hole correctly, then a slightly overset, underset or deformed rivet doesn't matter. I can't remember where I read it, but even quite poorly set rivets have 95% strength.

As for drilling out, I had all sorts of problems when I started. the answer was to stop using the air-drill - it's way too fast and wanders. I now use a battery powered hand drill where I can control the speed - much better results.

Bottom line for me now is that unless I have clinched the rivet or it is obviously grossly underset (wrong size) or overset (squashed flat) or the pieces arent lying together, I carry on. Much more likely to make a mess of drilling it out and trying again.
 
Tilford said:
....am terribly unsuccessful at drilling out rivets....
Click to expand...
Greg,

Bucking bars do slip. It happens. However, the rivet in the photo appears underset to me. Primarily for that reason, I do not see a compelling reason to replace the rivet at this point. With a bit more tapping with rivet gun and bucking bar, you should be able to form an acceptable rivet shop head. After flattening the shop head a bit more, examine it closely to make certain it does not show any signs of cracking (unlikely) but if it does, you really should drill out the rivet out and replace it.

You are way to early in the building phase to start balking about drilling out defective rivets. The common arguments you hear about not replacing marginal rivets is always questionable advice and I can assure you it is something you will NEVER hear in the production environment. Even highly skilled riveters mess up from time to time. Goes with the territory. Indeed, if a production worker went to his boss with such excuses, I can assure you that worker would either LEARN how to drill out defective rivets or be looking for another job. In the production world, the designers, the engineers, the regulators, and the paying customer all have expectations of acceptable work, of quality work. It is as simple as that. In this case, YOU are the customer. You are also your own QC department so no one can tell you what to do.

My advice is simple but the ramifications can be hard. Refuse to settle. You will ultimately become the better craftsman for it. ;)
 
When i went to A&P school in the early 80.s my airframe instructor was an old timer who always insisted in us using the pistol grip technique when using a drill ans specially when drilling out rivets.

Do you Remember when you used to play shotting at others with your hand!? Thumb up, index finger pointing out and all the other fingers tucked in? Thats the pistol grip technique! Use your middle finger to pull the trigger and your index to drive the drill bit direction. It gives you a better control and the visuals are better. There is no woobeling since your command of the drill is a lot better. It works better with air drills. (strongly reccomended for bulding) but it works as well with the bulky electric drills most use now days.

As for your rivet, i wouls like to see a profile picture before passing judgement. I want to see how fat it got. As for the inperfect rivet appearance....let it be....just dont make it a common practice...
 
Thanks Guys,

I rechecked the rivet using that handy tool from Avery's and it is slightly underset, about 1/32, I think the photo may exaggerate this. I'm going to leave it be.

Thanks for the quick and helpful replies.

Greg
 
Tilford said:
Thanks Guys,

I rechecked the rivet using that handy tool from Avery's and it is slightly underset, about 1/32, I think the photo may exaggerate this. I'm going to leave it be.

Thanks for the quick and helpful replies.

Greg
Click to expand...

Check it more accurately....:)

The Avery gauge is for a "perfect" rivet with a 1.5 D driven head.

1.5 D is 0.1875 - The min. diameter spec is 0.163.

http://www.vansaircraft.com/public/Specs.htm

If you really are 1/32 under the head is far too small (about 0.155)

As Rick said, just drive it a little more and it will sort itself out into a good rivet...:)
 
I agree with Mr. Galati on this one. A few more taps should level the shop head out. It's hard to tell from over head how driven the rivet is but if it's not driven enough then a quick burst from the gun will do it. If it's set well enough and you want to avoid over-driving it, practice with the trigger action of the gun. I find I can 'tease' tight rivets into place, close minor gaps before riveting, and level uneven shop heads with a light touch on the trigger. I would not expect a crack to form there from such a slight offset but Rick is right that you should check.
 
az_gila said:
Check it more accurately....:)

The Avery gauge is for a "perfect" rivet with a 1.5 D driven head.

1.5 D is 0.1875 - The min. diameter spec is 0.163.

http://www.vansaircraft.com/public/Specs.htm

If you really are 1/32 under the head is far too small (about 0.155)

As Rick said, just drive it a little more and it will sort itself out into a good rivet...:)
Click to expand...

Ok. I just turned 45 and like clockwork I can't see any darn think unless it's more than 18" away and in larger print. When I wear cheaters in the shop I trip over all the cords and hoses and knock over anything and everything on the workbench, that said, I put on the cheaters and re-rechecked by just measuring the rivet outright. The upset height measures 1/16 or .0625 and the upset dia. measures 9/64 or .140. So after referencing the Vans link above (thank you for that) and Standard Aircraft Handbook I think I'll smack it a bit more.

Thanks again!
Greg
 
For what it's worth, when I drill out a rivet, I use a spring-loaded center punch to mark the center of the rivet on the manufactured head (should be near the center of the little dimple on the head, but not always), then drill a 1/16" pilot hole about 1-2 mm deep, then follow with a 3/32" drill to about 2 mm, or just deep enough so that you can take a 3/32" punch and pry the head off. Then punch out the shank / upset head. Works well IMO.
 
Same pic?

Greg, I think you attached link to same pic as the original--at least rivet looks same to me. Might try another link.

Skyking
 
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