As a first time builder I am just starting to install nut plates on the rear spar for attachment of hinge assembly. I installed the nut plates as specified in the plan. Installation was no problem. After I installed them I took one of the apporpriate bolts just to make sure everything was OK. I started to thread the bolt in by hand and it seemed to start OK but quickly seemed to lockup. Do these nutplates have a self locking feature which would explain the fact that the bolts don't thread in easy? I was going to look at them closer but did not have a chance last night.
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Nut Plate Question
- Thread starter hjd3021
- Start date
stevemcgirr
Well Known Member
Yes they do
I'm sure you will get other responses, but nutplates are designed to lock the bolt and they do require a pretty significant amount of torque to thread in, ie you can't fully thread them in with your fingers
There is a "tip" on the EAA website, under the homebuilders link and the videos listed there, where it is suggested that you pre-treat the nutplates prior to bolt insertion, with a tap of appropriate size. This is not a good idea, IMHO, in places where the bolt needs to stay locked, but may be acceptable when the bolt will need to be frequently inserted and removed
I'm sure you will get other responses, but nutplates are designed to lock the bolt and they do require a pretty significant amount of torque to thread in, ie you can't fully thread them in with your fingers
There is a "tip" on the EAA website, under the homebuilders link and the videos listed there, where it is suggested that you pre-treat the nutplates prior to bolt insertion, with a tap of appropriate size. This is not a good idea, IMHO, in places where the bolt needs to stay locked, but may be acceptable when the bolt will need to be frequently inserted and removed
stevemcgirr
Well Known Member
Again, my opinion, but the number of places where loctite is a good idea is very infrequent. In most instances, you will be using nylock nuts, star washers, or some other mechanical means of locking the bolts in place
Look closely at one of your nutplates. You will see the threads are formed and then they are crimped on the outside parallel to the legs as a lock feature. Lots of past discussion here on tapping versus stretching versus leaving them alone. For me, its leave them pretty much alone on critical structure, stretch 'em where I need to, and I don't think twice about tapping some in floorboards or sometimes thin parts that get deformed from too much strong arming.
Rich_in_AK
Member
tapping nutplates
My general rule that I used on both my RV-8 and RV-7A is this: If a bolt goes through a structural component, leave the nutplate alone. If a screw goes through an inspection cover or other type of removable cover, then I tap it to make install/removal easier. I have never had a single screw come loose in operation and it saves a lot of screws from being ruined being stripped out with the screwdriver.
My general rule that I used on both my RV-8 and RV-7A is this: If a bolt goes through a structural component, leave the nutplate alone. If a screw goes through an inspection cover or other type of removable cover, then I tap it to make install/removal easier. I have never had a single screw come loose in operation and it saves a lot of screws from being ruined being stripped out with the screwdriver.
RVTrumpet
Active Member
I am pretty sure that the part of the nutplate that has the threads cut into it is not a completely circular shape, but just the slightest bit like an oval. This forces the bolt to expand the nutplate to the correct size. In this way, the oval shape put a force on the bolt similar to that or a lock-washer on a nut.
waterboy2110
Well Known Member
As a general rule - any locking nuts that can be threaded by hand are worn out and should be tossed. Nutplates are locking devices.
A screw in a nutplate (or a nut and a bolt) are NOT the same as a wood screw being driven into a piece of wood creating its own hole. Do not confuse how machine screws work with how we commonly see screws working in wood. It is a common misconception that screws apply a clamping force (or resistance to an axial load) due to friction in the rotary motion involved in their tightening. This is not the case for machine screws, where we are not driving them into a tree to hold up a hammock!
The clamping force comes from the tension and compression of both components (screw and nut or nutplate in which the threads are inclined planes in contact) once they begin to apply vertical force to each other. That occurs when the head of the screw in in contact with the holed surface and is tightened further - NOT before. For inspection panels, a lot of friction in screw insertion is a bad thing, not a good thing. Such a screw should never encounter enough resistance to cause the head to strip when being installed, or be difficult to install. It is a bad day for you when you strip the head of a screw in an awkward place. Get out the #6 or #8 tap and use it wisely on overly tight nut plates. Also the boelube. Just my opinion but I think the "controversial EAA video" is right on.
The clamping force comes from the tension and compression of both components (screw and nut or nutplate in which the threads are inclined planes in contact) once they begin to apply vertical force to each other. That occurs when the head of the screw in in contact with the holed surface and is tightened further - NOT before. For inspection panels, a lot of friction in screw insertion is a bad thing, not a good thing. Such a screw should never encounter enough resistance to cause the head to strip when being installed, or be difficult to install. It is a bad day for you when you strip the head of a screw in an awkward place. Get out the #6 or #8 tap and use it wisely on overly tight nut plates. Also the boelube. Just my opinion but I think the "controversial EAA video" is right on.
