sheet metal grommet for panels?

[coppercone2]

I see some equipment has grommets made of shiny metal installed on holes that feed wires. Very much like the kind you find on a curtain.

Do you just use the same stuff that is sold for like tarps on sheet metal for chassis, or is there better/purpose built stuff for this?

[floobydust]

I can't quite understand what you are looking for.
There are wire rivets on PC boards that have large wire flying leads, to prevent pads from getting ripped off.
Cable grommets are plastic to stop sheet metal sharp edges from cutting the wires.

[jpanhalt]

Is this what you are asking about?
https://www.electriduct.com/Round-Metallic-Finish-Desk-Grommets.html

There's no reason a standard plastic grommet can't be plated.  A grommet like used on traps would seem to be more difficult/expensive to install.  Rather than play a guessing game, please post a picture.

[coppercone2]

no, they have basically tarp grommets in chassis. Like the ones in a pair of jeans. But everyone I found is for textiles or soft materials in description, yet I see them in sheet metal up to say 1/2 inch diameter. Like for feed through into chassis mount inductors that are shielded.

https://www.amazon.com/CRAFTMEmore-Grommet-Surface-Replacement-Accessories/dp/B077TD6D7Z?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&psc=1&smid=A34X17GYN3LO6W

Like the electrical manufacturer of those

[IanB]

But everyone I found is for textiles or soft materials in description, yet I see them in sheet metal up to say 1/2 inch diameter.

It doesn't matter what they are "for". You can use them anywhere they will fit, if you so choose. It's up to you.

That said, a large box of assorted rubber grommets costs peanuts at Harbor Freight, so I don't see the point.

[coppercone2]

I assume there is a real manufacturer of these, something like keystone, since its used in electrical chassis. I want the nice metal one that is designed to have proper deformation over metal and to have a look at the crimp tool or anvil/etc for it.

For PCB eyelets, you will find its complicated/expensive to seat them properly, special tools are sold for each size.

It might be called a eyelet, but everything I find for them is small.

I would expect something like this with a larger tool
https://www.amazon.com/Grommet-Eyelet-Setting-Pliers-Grommets/dp/B0047AKK0Y

This is the closest I found
https://www.homedepot.com/p/General-Tools-Brass-Grommet-Fastening-Kit-with-Case-Includes-6-1-2-in-and-6-3-8-in-Grommets-81264/204763455#overlay

Every time I see something in electronics that is similar to something in arts and crafts, there turns out to be a better more precise tool made for it with science behind it. A large one like this I expect a benchtop tool like a button press or something. I know to avoid general tools. What is the swiss work shop version? maybe the one they use for swiss military flags designed to survive WW3 blast winds might be good.

All the big presses seem to be designed to work with cloth (bench top grommet press). I would love to hear one like 'blah blah has one of these tools for the last 50 years and the QA department found 0 fails in the last 30 years....'. Someone might know. Like a small transformer manufacturer (they are used in transformer shield feed throughs sometimes).

[Overspeed]

Hello

Brass / copper alloy can be glued ( extremely strong assembly ) by using Loctite 648.

No need to crimp , if you need only few , grommet can be made fron brass bar on a small lathe at reasonable cost

Regards
OS

[coppercone2]

I guess retaining compound would work, just need to verify that the area is flat. I imagine something bad would happen if you miss a bit of bur from a dull drill bit in sheet metal? IIRC that has a narrow tolerance for it to set in properly (flatness requirement). I actually have one dodgy chassis hole I left after a mod that needs fixing, and it would be a pain to take that apart (replaced a cord with a IEC connector) enough to properly add a gland, but you can glue a grommet in there. I see the teflon wire is still centered properly away from the hole edges (which I deburred but its shitty) after 6 years, but it does bug me still, it should be fixed nicely.

And if you use a punch press, I see those panels have more then the usual amount of deformation. I don't have one but I was thinking about buying a small one last year, would this process interfere with retaining compound? I gleam the deformation from youtube videos, perhaps they are over loading the press or the die is bad, but its the first thing that comes to mind when I think about the process, that it might be warped.

And do you know if there is a problem with using retaining compound on anodzied metal (aluminum?). Do you need the same prep work as for brazing/welding/soldering? I only ever used threadlocker on steel and stainless steel, I never tried the cousin on aluminum or annodized aluminum.

I found these guys, that sell supposedly sheet metal grommet. Interesting since it looks like you could theoretically use a star washer with the grommet to make a conductive lip on aluminum. If anything, that might be a different way to offer a chassis ground contact for meters, but I guess a brass stud would be preferred. Like if you put a star washer and grease in there in addition to the sheet metal grommet assembly, it might work to provide a contact point for painted or annodized metal that is reliable.
https://stimpson.com/grommets-washer-overview/sheet-metal-grommets/

And that made me think of something else, to make a universal kit for adding a chassis connect banana jack to any equipment you are working on (various thread sizes) so you can plug a banana jack into the inside while you are working on it. For HP, I stuffed banana jacks into the holes in the frames before, but I wonder if you can attach them into a hole with a modified cleco rivet clip to make a durable one. Alligator clip always kind of sucks. It gets a little ugly once you remove the front panel and the front ground is disconnected. Or just use a modified banana jack with a thumb screw.


http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-G/MIL-G-16491F_16004/

[Overspeed]

Hello

copper on aluminium = nice Seebeck effect , normally aluminium is anodized to avoid conductivity and avoid corrosion or if that a request to keep conductivity a treatment as the chromium passivation is the solution but bare brass ou copper shall be avoided for Tin or Silver coating parts

Regards
OS

[coppercone2]

but do you trust that compound on a anodized aluminum object that is probobly greasy (can you clean it enough with a spray or wipe)? Or would you sand it down first so its flat metal?

I noticed I had exceedingly poor results with superglue on anodized aluminum (that was cleaned with 100% isopropyl alcohol spray and wipes). It was almost like a mold release. I try to use alcohol from a pressurized can for pre-glue cleaning.

[Overspeed]

Hello

Anodizing is porous and even after dying they stay porous except if the anodizing is sealed  , but that not a problem for gluing / bonding IF the surfaces are clean / dry clean  , I use acetone to make a deep cleab before gluing , alcoll is not efficient enough or grease and other greasy pollution . 

Loctite 648 is a bonding compound , extremely strong bonding effect and that not a cyanoacrylate as superglue , cyanoacrylate glue are strong but brittle , Loctite propose a black cyanoacrylate which is a bit more efficient for mechanical purpose but not at the level of the 648 .

Two pieces bonded with 648 need a lot of force , brute force to destroy the bonding including propane torch heating

Regards
OS

[coppercone2]

How do you compare the retaining compound to epoxy?

I thought to get a vial of it, I have purple red blue green threadlockers. Retaining compound I think is some what similar to green thread locker.

And is the shelf life as good with thread lockers, where they seem to be good.. way past the expiration date? I ask because I usually have epoxy I need to throw away (I pay the epoxy in stock tax), I can see retaining compound being convenient, but its also just possible for me to use epoxy instead of throwing away 20% after it stops curing nicely.

The fit needs to be really good for the retaining compound right? (very high flatness requirement)?

Oh right, and this question was asked but never answered. If I restored a transformer, and put retaining compounds between all the plates, would that be a good transformer? I know you should varnish it, which I do, but it seems that retaining compound between the laminations would be superior to varnish getting sucked in there.

[Overspeed]

Hello

Bonding small surfaces with epoxy is difficult when surface are flat , can be ok to bond / glue insert in holes , epoxy is bit brittle , Loctite is shock tolerant .

Loctite ( or similar ) looks similar except the color but the tensile result is not the same , serie 200 is for thread locking so some thing mild and light as viscosity , the 600 serie is designed for maximum bonding effect and tensile performance .

I bond parts with 648 since 20 years with no concerns and very good results

Regards
OS

[coppercone2]

alright I bought 10mL

I came across flat metal to metal joints frequently.


Can it be used to do something like attach a chassis bracket (L shape)? If you have a panel that sits on the bottom, and you want a perpendicular mounting surface, no problem to bend something into a L and then use retaining compound to seat it? The PSI rating is similar to epoxy, near 4000. For like mounting a PCB sideways.

[Overspeed]

Hello

Adhesive testing article

https://www.researchgate.net/publication/281283390_Review_of_Tests_for_Adhesion_Strength

Be awre of one detail , Loctite 648 is an anaerobic glue so only the compound without air will go hard and glue , that important to metter the right quantity and to remove the excess not solidified with acetone and a piece of fabric ( cotton works ok )

Regards
OS

[coppercone2]

I am going to attempt to reinforce the side of a altoids tin wall by clamping a aluminum plate on it with the retaining compound. I will sand and clean both surfaces, clean with solvent, the clamp.


The idea is to use altoids tin to make various battery boxes, this one being a 3xAAA box with banana plugs, but I also want to make a 5xAAA box when I get some shorter banana plugs, and maybe a 12V box with primary lithium cylinder cells.

[coppercone2]

is it suitable for this task? after 20 min it came right apart (it was not set at all). Maybe I did not clamp it too good so what I did now is put 3x small vise grips on it real tight, not sure how flat it is, hard to tell because its hidden behind the lip of the altoids tin. . It is a 1 inch by 3/8inch aluminum piece that has two deburred holes in it, that are placed against an altoids tin interior. I sanded and solvented both mating surfaces.

I see the cure time is gap dependent, so I will check on it tomorrow. If it fails again I can put it inside of the big vice with some blocks to apply pressure uniformly to the correct area. I enjoy working with this stuff alot more then glue, no sticky mess, I hope it could work for these kinds of applications, like reinforced altoids tins.