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Rivet size
- Thread starter miyu1975
- Start date
Not sure I understand the question. 426 4-5 The 426 3.5 is throwing me a curve.
426 is the type of rivet (countersunk head)
The following "4" is the diameter (4/32" or 1/8")
The -5 is length (5/16")
If you are truly asking if there is a 426 5-5, then yes. It would be 5/32" dia by 5/16" long.
426 is the type of rivet (countersunk head)
The following "4" is the diameter (4/32" or 1/8")
The -5 is length (5/16")
If you are truly asking if there is a 426 5-5, then yes. It would be 5/32" dia by 5/16" long.
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flion
Well Known Member
Like Mel, I find your description a little confusing. However, since you mentioned you drilled out a HS skin rivet, I'm guessing you meant an AD426 3-3.5, in which case you can use an 'oops' rivet (search the term for more info in this forum) or an AD426 4-4. The latter will be noticeably larger than the other skin rivets but I'll bet it'll be unnoticeable on the finished aircraft unless you point it out. So many rivets ...
dhall_polo
Well Known Member
other ideas...
Going from a -3 rivet up to a -5 sounds like you had some fun drilling out that rivet.
Rather than stepping up in rivet size, maybe just cut out a small square of alum from scrap, drill a -3 or -4 hole into that, and add that to the bottom of what you're riveting?
Going from a -3 rivet up to a -5 sounds like you had some fun drilling out that rivet.
Rather than stepping up in rivet size, maybe just cut out a small square of alum from scrap, drill a -3 or -4 hole into that, and add that to the bottom of what you're riveting?
flion
Well Known Member
The backing tab from scrap may not help if he's widened the hole so much that it would take a #5 rivet to fill it. Mel would probably give the best advice on whether or not the skin needs to be replaced as well but I would be tempted, if it is only a single rivet, to fill the hole with Hysol blue and then re-drill for a #3 rivet and back it with the scrap tab. I think the Hysol would provide enough support for the rivet once countersunk and the tab would support the structure and keep the rivet (longer, of course, AD426 3-4 or -5) from pulling back out. I have a couple of Hysol filled holes on my skins where I mis-adjusted the countersink, but the structure underneath was OK.
Rick6a
Well Known Member
This is one of those many times referring to drill index chart can answer a lot of questions and even help you decide on possible options. Lets look at your case specifically. Using a #40 drill, the hole is supposed to be 3/32" to accept an AD3 rivet. Referring to a drill index chart, you find that a #40 drill bit equates to .0980 diameter. But the hole is now too big for that. So you correctly decide to go to the next rivet size which is a 1/8" AD4 rivet. Using a #30 drill bit, the hole is enlarged to .1280 diameter. You have found the damaged hole is still too large to accept even that diameter. Now you are in a pickle but the situation is not hopeless. You still have a couple of options.
You could ream the hole for an AD5 rivet which is a 5/32" diameter using a #20 or #21 drill bit. Referring to a drill index chart, you find that a #21 drill equates to .1590. That is a fairly large hole and you may not have enough edge distance or possess a dimple die to accept its flush head. Even if you can meet those requirements, you may have trouble setting the shop head on a solid rivet without causing even more damage. Probably best in this case to use a pulled blind rivet instead of a solid rivet but cosmetically its size will surely stand out in an AD3 rivet pattern.
Short of scrapping the parts and starting over or fabricating a patch as discussed previously or going with a 5/32" rivet, consider this alternative: Instead of bringing the hole up to a large .1590 for an AD5 solid rivet (or 5/32" pulled rivet), enlarge the hole to a much smaller 9/64" diameter which is .1406 diameter and install a readily available MS24693 flush head screw and locknut instead of a rivet in this single location. You probably have a dimple die to fit this screw and its dimple is just slightly larger than that of an AD4 rivet head so its presence will not be all that obvious. Be aware that a #6 MS24693 is not a structural screw. It is up to you to decide its suitability. Also be aware that to use a structural screw, you'd have to enlargen the hole to accept a #8 MS24694 and if you did that, you'd only be slightly better off than just using a 5/32" pulled rivet as Mel suggests.
flion
Well Known Member
When in doubt, follow the DAR's advice...
I doubt, especially after paint, that it would be very obvious. If you have a hand deburring tool that uses the three-flute countersink bit then you can carefully enlarge the dimple to fit the pulled rivet. My method above has the advantage of letting you use a #3 solid rivet but is a little more difficult. The screw method would also work but you now have an inspection item, an insignificant weight increase, and a screw head to fill. But after seeing the pics I don't think you'll need to replace the skin.
However, you might want to practice drilling out rivets. You'll be doing more; with a little practice you can get them out fairly cleanly. I invested in #40 and #30 punches so that I could drill the heads off and use the punch to break off any remaining attachment and drive out the body of the rivet. I managed to have to replace a fair number of rivets but never had to use an 'oops' rivet.
I doubt, especially after paint, that it would be very obvious. If you have a hand deburring tool that uses the three-flute countersink bit then you can carefully enlarge the dimple to fit the pulled rivet. My method above has the advantage of letting you use a #3 solid rivet but is a little more difficult. The screw method would also work but you now have an inspection item, an insignificant weight increase, and a screw head to fill. But after seeing the pics I don't think you'll need to replace the skin.
However, you might want to practice drilling out rivets. You'll be doing more; with a little practice you can get them out fairly cleanly. I invested in #40 and #30 punches so that I could drill the heads off and use the punch to break off any remaining attachment and drive out the body of the rivet. I managed to have to replace a fair number of rivets but never had to use an 'oops' rivet.
GAHco
Well Known Member
These are the Real Deal!
The NAS1241's are Countersunk and 1/64th oversize, the NAS1242's are Universal Head.
These can fix slightly large hole issues that are un=detectable from the head side, and barely noticeable from the tail side.
[URL="http://www.gen-aircraft-hardware.com/images/pdf/solid_rivets_Oversize.pdf"]http://www.gen-aircraft-hardware.com/images/pdf/solid_rivets_Oversize.pdf[/URL]
We stock the popular sizes and can get many others.
Normally stocked in 1/4# bags, Special order item 1#, unless you have data (not just a feeling) that I would be selling many more to others, then I would consider making it a standard "stock" item.
The NAS1241's are Countersunk and 1/64th oversize, the NAS1242's are Universal Head.
These can fix slightly large hole issues that are un=detectable from the head side, and barely noticeable from the tail side.
[URL="http://www.gen-aircraft-hardware.com/images/pdf/solid_rivets_Oversize.pdf"]http://www.gen-aircraft-hardware.com/images/pdf/solid_rivets_Oversize.pdf[/URL]
We stock the popular sizes and can get many others.
Normally stocked in 1/4# bags, Special order item 1#, unless you have data (not just a feeling) that I would be selling many more to others, then I would consider making it a standard "stock" item.
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Norman CYYJ
Well Known Member
If it looks like things are going to look ugly drill a new hole close to the damaged hole and use the proper size rivet with the correct edge distance and fill the bad hole just prior to painting. Unless someone is counting rivets no one will see it.
