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Passing a flare nut through a grommet

Draker

Well Known Member
Vans baffle assembly instructions call for a AN941-6-16 grommet to secure the prop oil line, where it comes up through the right air ramp and feeds in behind the starter ring gear. This grommet’s inner diameter is 3/8” which snugly fits the oil line, but does not allow the existing flare attach nut to pass through. Any tips that don’t involve making a new prop oil line?

 
Grommet

Warm it up, apply some lube and work it. I've worked quite a few grommets and o-rings over stuff I never thought they would clear.
 
If Larry’s method doesn’t work, in this case you can just slit the grommet with a razor blade, put it on the tube, and pop it into the hole. The slit won’t pass any significant amount of air - but if it bothers you, just goop the area up with RTV when you seal everything else.
 
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If Larry’s method doesn’t work, in this case you can just slit the grommet with a razor blade, put it on the tube, and pop it into the hole. The slit won’t pass any significant amount of air - but if it bothers you, just goop the area up with RTV when you seal everything else.

Yep, what Paul said. Split grommet is a common way to deal with stuff like this.
 
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Thanks. After spending way too long trying to jam this in I’m just going to split it when the time comes.
 
Try cyanoacrylate

Thanks. After spending way too long trying to jam this in I’m just going to split it when the time comes.

Slit on the table with a sharp razor in a straight line, then after installation in the desired location, you can glue it with super glue. Clean with isopropyl alcohol to be sure it is clean.

In one of my engineering assignments a chemical engineer for non-metallics sat next to me. She was making prototype o-rings for the lab. Now, she cut the extrusion at a 45 deg angle, but they did need to stretch. I have extra o-rings of larger diameter (correct cross section) and successfully made a few.

Give it a try with a spare to be sure of the specific compatibility. Personally have found the splits are so tightly closed by the exterior they are invisible anyway.
 
No slitting required. Get your socket set out, push it on to one that is slightly larger than the ID then line that socket up with one that is slightly larger. Keep passing it back and forth between slightly bigger sockets. You can get one of these bushings quite stretched out with this method. Once you have it to the ID you need just push it on to the nut. It sometimes takes a couple tries but it works beautifully!
 
Nice! I used Jereme’s socket method to get it into a -6D threaded bulkhead union. Then just screwed the nut onto the fitting and the grommet transferred over the nut easily. Thanks!
 
Methinks when you get to installing the grommet in the baffle you may want to revisit the idea of splitting it.
 
Methinks when you get to installing the grommet in the baffle you may want to revisit the idea of splitting it.
Exactly what I was thinking - getting this grommet over the nut is the easy part. Getting it into the baffle nicely I found was next to impossible. I ended up using some of my silicone baffle material to "seal" the hole and used the grommet to hold the baffle material in place. I figured I'd wait for a good tip on VAF to figure out how to do it right! :)
 
Get one side started and then you can use a small screwdriver to put pressure on the part of the bushing that's not in yet. Then you can use your finger on the other side to pull the "wing" of the bushing out. You are basically working it around the perimeter a little bit at a time. It sounds more complicated than it is. Just keep working it. After you do it once it will be easy. Ask me how I know... :)
 
Grommet

Get one side started and then you can use a small screwdriver to put pressure on the part of the bushing that's not in yet. Then you can use your finger on the other side to pull the "wing" of the bushing out. You are basically working it around the perimeter a little bit at a time. It sounds more complicated than it is. Just keep working it. After you do it once it will be easy. Ask me how I know... :)

What he ^ said. I also have a rounded angle probe I use for this. A little silicone grease to lubricate and work it in. I've put in a few VW windows. :D
 
What he ^ said. I also have a rounded angle probe I use for this. A little silicone grease to lubricate and work it in. I've put in a few VW windows. :D

There was a neat trick for installing old VW windows, which was to put a loop of cord into the rubber seal's groove. Then, position the window up against the metal frame and pull on the cord to flip the rubber lip inside the frame. It might also work for grommets, using dental floss or lacing cord or something similar.
 
There was a neat trick for installing old VW windows, which was to put a loop of cord into the rubber seal's groove. Then, position the window up against the metal frame and pull on the cord to flip the rubber lip inside the frame. It might also work for grommets, using dental floss or lacing cord or something similar.
I can see how that might work - cool tip!
 
Getting it onto the baffle was not nearly as difficult as getting it around the nut. Of course I’m gonna have to disassemble it all later to hit those three rivets connecting the right front baffle. I do so many things twice by not reading ahead in the plans!
 
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