will rivnuts make contact in 3/4 4130 tubing?

[buchdvm]

I want to substitute rivnuts fot sheet metal screws for installing the windshield on a Zenith 750. Will they make contact and hold?

[Aaron Novak]

I want to substitute rivnuts fot sheet metal screws for installing the windshield on a Zenith 750. Will they make contact and hold?

Yes, keep in mind however that the diameter of the hole needed will be larger than for a sheetmetal screw ( i.e. probably not the best idea to punch a 1/4" hole in a 3/8" tube). But yes, rivnuts are designed to work with both flat and curved surfaces, and are used frequently for tubing. I would personally pick a size that meets the same pullout strengths as the original sheetmetal screw. Cardinal components should have the engineering data on the rivnuts.
-Aaron

[RV8505]

I want to substitute rivnuts fot sheet metal screws for installing the windshield on a Zenith 750. Will they make contact and hold?

I would stay with the steel on steel use of a sheetmetal srew.. It is alot stronger than a rivnut and you will less likely get any corrosion. You can always blow the hole out later it it strips out and use a rivnut.

[buchdvm]

Thanks Aaron your comment was very helpful

Ken

[WLIU]

You should also consider that a rivnut starts out much longer than its finished length. So if you intend to drill into one side of a tube, you should check the raw length of the rivnut to see whether it will sit fully into the tube before you pull it to its finished, shorter length. With the right technique you can push it into the tube as the puller does its job of forming the interior clamping bulb, but it requires some finesse and in some situations may not work. Drilling out a rivnut is a pain in the butt.

I will suggest that many airplanes attach their windshields with machine screws and fiber lock nuts where the machine screw sits in a hole drilled all of the way through the mounting structure.

Best of luck,

Wes

[Aaron Novak]

I would stay with the steel on steel use of a sheetmetal srew.. It is alot stronger than a rivnut and you will less likely get any corrosion. You can always blow the hole out later it it strips out and use a rivnut.

Rivnuts come in many materials, I guess I had assumed ( poor on my part ), that the OP would use cad plated steel ones. Good catch!!

[RV8505]

Rivnuts come in many materials, I guess I had assumed ( poor on my part ), that the OP would use cad plated steel ones. Good catch!!

Aaron, I just checked Aircraft Spruce, They don't have steel rivnuts. So I would imagine they might be availiable from maybe Genuine aircraft hardware? I don't know if you could pull steel rivnuts with the tooling commonly availiable to us in light aircraft building. I think they would be pretty tuff to pull. I would suppose you would have to have Kung Foo grip or a Hydraulic puller of some type. I think it would pull all of the threads of my B.F. Goodrich rivnut puller trying to pull steel rivnuts. I don't know, I have never tried to pull steel rivnuts. I have seen them in industrial applications but I was unfamiliar with their installation and type.

I do know if your going to put aluminum aircraft in get rivnuts that have a little key to help keep them from rotating when you put a screw in them. I have a key cutter for aluminum but I wouldn't try it on steel tubing as it would break. So for steel you would have to file a tiny key for the rivnut to grip.

I have another idea, If the ends of the tubing are open use nut plates and and pull type nut plate rivets.

[WLIU]

I have to say that the sum total of the discussion has convinced me that following the plans and using sheet metal screws is the best solution unless the tube in question is going to be replaced with a C-channel that can accommodate nut plates. You do not remove the windscreen any more often than once every maybe 5 years, so I suspect that the original designed did not expect you to wear out the holes.

Sinple and light is good. As the suggested complexity and weight increases, the original design looks better and better.

Best of luck,

Wes
N78PS

[RV8505]

I have to say that the sum total of the discussion has convinced me that following the plans and using sheet metal screws is the best solution unless the tube in question is going to be replaced with a C-channel that can accommodate nut plates. You do not remove the windscreen any more often than once every maybe 5 years, so I suspect that the original designed did not expect you to wear out the holes.

Sinple and light is good. As the suggested complexity and weight increases, the original design looks better and better.

Best of luck,

Wes
N78PS


WES, Are the ends of the tubes unwelded? If it is, You can snake a nut plate up there with some safety wire and grab it with a cleco and use a nut plate rivet. I have a whole bunch of nut plate rivets. I'll give you some if you need them.

[nrpetersen]

If you do use sheet metal screws into 4130 tubing, use a tiny amount of anti-seize on each screw tip & then you can adjust the number drill size to a slightly smaller dia to get a better thread. Anti seize paste makes them much easier to drive also.

[WLIU]

buchdvm is the guy who asked the question. I believe, from looking at one airplane, that the ends of the tube are welded to other structure and access is not possible through the ends.

The anti-seize suggestion is a good one.

Best of luck,

Wes
N78PS

[Aaron Novak]

Aaron, I just checked Aircraft Spruce, They don't have steel rivnuts. So I would imagine they might be availiable from maybe Genuine aircraft hardware? I don't know if you could pull steel rivnuts with the tooling commonly availiable to us in light aircraft building. I think they would be pretty tuff to pull. I would suppose you would have to have Kung Foo grip or a Hydraulic puller of some type. I think it would pull all of the threads of my B.F. Goodrich rivnut puller trying to pull steel rivnuts. I don't know, I have never tried to pull steel rivnuts. I have seen them in industrial applications but I was unfamiliar with their installation and type.

I do know if your going to put aluminum aircraft in get rivnuts that have a little key to help keep them from rotating when you put a screw in them. I have a key cutter for aluminum but I wouldn't try it on steel tubing as it would break. So for steel you would have to file a tiny key for the rivnut to grip.

I have another idea, If the ends of the tubing are open use nut plates and and pull type nut plate rivets.

The OD of the cad plated rivnuts are typically ribbed, and are easily pulled with a hand tool.