In need of Nutplate 101

Good morning, everyone.

I am in need of some nutplate 101.

I have been dreaming of some features and upgrades to my airplane, and a few of those upgrades include many nutplates. For instance, attaching fiberglass tips with nutplates instead of blind rivets, or using nutplates on the seat and baggage floors so they are removable. (I don't want a big discussion on why I'm doing those things, just choosing those as examples in my nutplate dilemma.)

After doing a quick search of aircraft spruce for "anchor nuts" (can't search for "nutplate"... no results) I've found there are many varieties of nutplates.
http://www.aircraftspruce.com/catalog/hapages/anchornuts.php

I have figured out, for instance, that I'll want a dimpled nutplate where I need a flush fastener and the material isn't thick enough to countersink, but my main question is:

How do you decide what size nutplate to install?

The biggies seem to be #6 (6-32), #8 (8-32), and #10 (10-32), but I also see some #4 (4-40) out there.

Also, there are K1000 (Full Size) and MK1000 (Miniature). Why wouldn't I use the miniature ones where possible?

I am a little familiar with the K1100-6 (K1100 is the full size dimpled) nutplates from the trim access cover on the left elevator, and those screws are nice and small.

But isn't smaller the better aesthetically? Would 4-40 be too small for the fiberglass tips? (I haven't held a 4-40 in my hand since my model airplane days, it may be obviously too small.)

Also, for the baggage floors, I'm not as concerned with screw head size. Would #8, or #10 (I think #10 would be an AN509 screw; the ones used to attach the counterweights) be better there? (From reading past threads via the search feature, it looks like people are torn between using the pop-rivets, or using nutplates, but people are liking the #8 if they go with nutplates.)

I'm an engineer, and could probably pull out a textbook to do some analysis on the shear strength of the rivets they are replacing, but I figured someone would have a good rule of thumb for me to use.

Anyone have some good pictures of nutplate installations in any of these areas?

Thanks in advance.

Nutplates add weight (and frustration). Believe me you will install plenty on your project. You won't enjoy them by the time your done. Still the wing tips and some other spots need nutplates and you do well with 6/32's. Smaller than that won't work in most apps. 8/32 are common. There are very few 10/32 and larger. Floating nutplates and fiberlocks are $$$ and uncessary. In most cases Van's calls out the appropriate nutplate and I found no need to deviate.

The full size K1000's are easier to work with then the miniatures. There are some places where there's not enough space for the K1000's so you have to use a miniature. You'll also find that in some places you'll need to a single lug nut plate. As was said in the first reply, you'll use mostly 8-32's and 6-32's.

Nut plates for the wing tips are fairly common place and well worth it.

It's been a while since it did the emp but when you refer to "dimple" nut plates are you referring to the nut plates for Flush screws where you dimple the screw hole. As I recall, Van's doesn't supply any nutplates where the lugs a dimpled.

Most places in the interior (like the seat pans) don't require flush screws.

I know that a few people install the baggage floors with nutplates but it adds lots of work. Think "drill & deburr" 3 holes (and dimple 2 of them) for a nut plate vs 1 hole for a pop rivet. If you really want to remove the baggage floors, drilling out pop rivets is pretty easy.

Use oops rivets to avoid dimpling.

Even on very thin material you can counter sink with a 100 degree deburing and c'sinking tool and use an oops rivit. The oops rivit has a very small head. The oops rivits are NAS 1097. I got the avery kit part # 1097k for $12 at Sun N Fun. The kit has 3/32 and 1/8 rivets. You would use the 3/32 for the nut plates.

Yeah, I've been using oops rivets for my nutplate attach rivets so far with great success.

The dimpled nutplates I am referring to are the K1100 (versus K1000), the screw hole has been dimpled, so the dimpled material to which the nutplate is attached sits nicely in the nutplate. These are used in the trim access plate area.

I realize the baggage floor area nutplates are extra work, and there have been many threads about this in the past, so I'm not going to bother everyone with that discussion again. I am a long way (and lots of frustrating nutplates away) from needing to make that decision.

Anyone used the 4-40 nutplates for anything in their airplane? Too small?

I use them a lot!

I call them platenuts although the various old mil-specs called them platenuts, Anchor nuts and nutplates. They are a nut not a plate in my book but that's just my view once when I was a young inspector on the production line I asked a senior inspector about the multiple name uses and he told me a platenut is a part and a nutplate is an assembly - Ok that probably doesn't mean anything to you but it stuck with me.

I use only #8 platenuts and except where I have to use miniture or single flange parts because of location, I use full size double flange fixed platenuts. The use of fixed nuts forces precision techniques for installation. Dimpled platenuts and floating platenuts have the same hole pattern as the fixed standard platenuts. You can use a fixed #8 (8/32) platenut as a drill guide for the other two. First drill a #30 or 1/8" hole then clecoe the platenut in position (on either side) with a 1/8" clecoe, then drill one mounting hole with a #40 drill and clecoe that hole with a 3/32" clecoe to lock everything in place before drilling the final mounting hole. You can ignore the minimum thickness rule and countersink the mounting holes in the aluminum for flathead 3/32" rivets. Open the screw hole to 3/16" or so to allow installation of the screw upon structure assembly then rivet the platenut in place. In spite of your best efforts you will sometimes have some nuts in a pattern that are not perfectly aligned relative to all the others in the pattern. In those cases mark the worst offenders (hard binding screw installations or screws that simple cannot be installed) and progressively drill them out and replace them with floating platenuts until the entire assembly goes together smoothly. Areas where I use the dimpled platenuts are assemblies with the screw head in the slipstream like the wingtips lower rudder cap, fin cap over the NAV antenna, landing gear fairings and the access covers I made to close the elevator and rudder attach bolt access holes.

Platenuts are expensive but I stick with my subset of options and buy a lot of them at a time so they are on hand when I come up with a speed mod idea. It is a definite progress block if you have to stop and order parts.

You have to learn a lot by doing - good luck.

Bob Axsom

I'm using 4-40's

I am using the #4's (4-40) in all my tips - wings and elevator - as well as the bottom rudder fairing. My only piece of advice on this is get the #4 countersink and dimple dies to go with them if you decide to go that route. The bottom dimple die is smaller making it fit better at the wing tip. I didn't and initially used a #30 which caused smilely's on the wings when I dimpled the screw hole. The #4 die set should alleviate that issue. I am using #4 torx screws I got from Micro Fasteners which work better than the #4 screws that was part of the wingtip kit that Cleveland Tools sells that I started with. I bought additional K1000 style nutplates from Cleveland with a few floating one lugs from ACS when I ran out. The countersink and dimple dies were bought from Cleveland as well.

N999ZA said:

...... am in need of some nutplate 101..... isn't smaller the better aesthetically? Would 4-40 be too small for the fiberglass tips?..... Also, for the baggage floors, I'm not as concerned with screw head size. Would #8, or #10 (I think #10 would be an AN509 screw; the ones used to attach the counterweights) be better there? .....Anyone have some good pictures of nutplate installations in any of these areas?

Click to expand...

I am a huge fan of nutplates and have installed them in more applications than any other RV builder I am aware of. Here is a one-of-a-kind non-traditional application:


I dismiss the common assertion that nutplates add unnecessary time and weight to the project as a wholly irrelevant argument that speaks more to that builder's priorities and perspective than anything else. However I do consider using a proper nutplate jig as a huge advantage to quickly and precisely locate and drill nutplates to the structure with accurate repeatability over and over again. The majority of these jigs were found on eBay at a fraction of new retail price.


#1. Using NAS1097 rivets to attach nutplates is the aerospace industry standard and following those standards, have NEVER felt the need to add dimples to a single nutplate. Thin material is not an issue when using NAS1097 rivets:

http://www.vansairforce.com/community/showthread.php?t=56010

#2. Cockpit floors: For the most part, I used #6 nutplates except around the floor perimeter, areas where I used #8 nutplates and screws. The larger size of a #8 screw makes working with a driver a bit easier when installing or removing the screws. A cordless screwdriver can access a majority of the screws.


BTW, I have found need to remove the floors on more than one occasion and find the utility of nutplates in this application to be extremely useful. The 3 hour time investment it took me to install approximately 85 nutplates on this RV-8 floor seems a pittance in the overall scheme of things.


#3. Like many builders before me, I installed the wingtips using the #4 wingtip screw kit available from Cleaveland. For my tastes, the pattern of #4 screws along the wingtips is visually pleasing and works just fine. For cosmetic reasons only, I chose to use #6 screws and nutplates on all the empennage tips:


#4. I used screws and #8 floating type nutplates to attach the upper cowl on my -6A. Originally, I used Tinnerman washers under the screw heads but eventually removed them from the cowl and everywhere else as unnecessary.


In addition, nutplates were extensively installed FWF to help attach one accessory after another. As you can see, free use of nutplates is an expression of who I am as a builder yet both my RV's came in at or UNDER average reported empty weights. From my POV, the "additional weight" bromide is entirely meaningless when compared against my real world operational experiences.

Rick,

Those were the exact examples I was looking for.

Thank you so much.

(You don't happen to have a picture of your #4 screws in your wingtips, do you?)

N999ZA said:

....a picture of your #4 screws in your wingtips, do you?)

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Andrew,

Unfortunately, I cannot locate a real good close up wingtip detail shot but I cobbed this one together from what I do have to illustrate how some builders might install the wingtips using the Cleaveland wingtip #4 screw kit. In my case, I bonded a simple .025 strip of aluminum to the inside of the tips and attached the nutplates to it. Slightly countersinking the fiberglass on the opposite side, I used (as always) NAS1097 rivets. The first picture may give you an idea of the installed look you can expect.

That looks extremely sexy (sorry if I'm being forward).

Looking back, would you have used #4s on your emp tips if you could do it again?

N999ZA said:

.....would you have used #4s on your emp tips if you could do it again?

Click to expand...

At the time, I did give it some thought and decided #8 screws just looked too out of scale in that application and the much smaller #4 screws are easily damaged. A compromise between looks and utility, I chose #6 screws, and yes, I would do the same thing again. There is nothing right or wrong about such decisions. Everybody sees things in their own way.

The plane I bought has 4-40 screws in the wingtips. I would prefer #6. I throw away 30-40% of the #4s whenever I remove them. It may be installation/removal error on my part.

Tip screws

I found the #4 tip screws just too fragile, and ended up with #6 screws and K1000 nutplates. I use the stainless Torx head screws from Microfasteners.com and find them to be very reliable, and 99 percent reusable. I have had to remove my tips several times, and this system works well. I use them on my wheel pants, and access covers on the exterior of the plane. The screws are not structural in strength. You really need a quality Torx driver bit to ensure consistent results. I use the Snap-on drivers on my plane and at work( auto mechanic/machinist) with great results. There is a huge difference in fit and quality from the various manufacturers of Torx bits.

About halfway through my RV-9A project I discovered the nut plate jig. Absolutely required IMHO. I actually wore one out and need to purchase a replacement. You can build a plane without them, but just like a tungsten bucking bar, once you use one, there is no going back.

I have not tried the NAS 3/32" oops rivet yet, but from all of the good press on this forum, I intend to.

Regards,
Chris

#4 - torx is the trick

If you are going to use #4 nutplates, I believe using #4 torx screws is the trick. I tried the phillips type first but they strip out too easily even with the bit I got with the kit. As always having the proper tool helps out alot.

Just a note on the nutplate jig. For the K1000 rivet spacing you can buy a #6 and use it for #8 as well. Just drill the screw hole for the #6 first, then drill for the rivet spacing next with the jig and then drill the screw hole to #8.

I might have gotten this tip from Rick.

Rick6a; #1. Using NAS1097 rivets to attach nutplates is the aerospace industry standard and following those standards said:

NEVER [/U]felt the need to add dimples to a single nutplate. Thin material is not an issue when using NAS1097 rivets:

.

Click to expand...

Rick, Thanks for the PICs and detailed post. I did a search on Spruces website using NAS1097 AD3 rivet and came up with nothing. It seems that they only sell 1097 rivets in a 1/8th inch diameter shank. I may be missing something but aren't most platenuts attached with dash 3 rivets.

Avery has them...

Maxrate said:

Rick, Thanks for the PICs and detailed post. I did a search on Spruces website using NAS1097 AD3 rivet and came up with nothing. It seems that they only sell 1097 rivets in a 1/8th inch diameter shank. I may be missing something but aren't most platenuts attached with dash 3 rivets.

Click to expand...

...in a neat little box....

http://www.averytools.com/pc-918-73-oops-hole-saver-rivet-kit.aspx

Yes... you do need the -3 diameter for the nutplates.

NAS rivets

Thanks gill. That will be in my netxt order.

Maxrate said:

Rick, Thanks for the PICs and detailed post. I did a search on Spruces website using NAS1097 AD3 rivet and came up with nothing. It seems that they only sell 1097 rivets in a 1/8th inch diameter shank. I may be missing something but aren't most platenuts attached with dash 3 rivets.

Click to expand...

Mark,

Wicks has a healthy selection of 1097AD3 rivets in various grip lengths. If I were to recommend only one length to purchase, it would be the NAS1097AD3-3.5 as the most versatile, used approximately 85% of the time. I do not use any length shorter than that, myself. Buying all the available sizes would be ideal, but for most builders that is not very practical. With that in mind in addition to the -3.5, you could also buy the -8 length and then easily cut em down to proper grip length as required. Those two sizes will serve any needs likely to arise.

http://www.wicksaircraft.com/catalog/product_cat.php/subid=10145/index.html

Rick,

Thanks for the link. Having owned Cessnas in the past it is nice to take a peek once in a while in areas where you need an inspection plate/floor pans/etc...

Very nice post.

Fearless said:

If you are going to use #4 nutplates, I believe using #4 torx screws is the trick. I tried the phillips type first but they strip out too easily even with the bit I got with the kit. As always having the proper tool helps out alot.

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Did you try running a tap through the plate nuts on installation? Reduces their grip a little so the screws come out without stripping but don't vibrate lose.

Pete

PS If I did it again I think I would use #6!