Looking for a captive nut of a different variety 4

[geesamand]

I have an application where I am joining two plastic panels around the perimeter. We're using bolt,nut, lock washer, and plastic washers but it's way too many pieces. We've tried using u-nuts but in this application we don't like the gap between the panels created by the leg of the u-nut.

(To be clear, a U-nut looks like this:

http://www.trfastenings.com/pages/multi+thread+u+nuts)

I'm looking for something similar that is sized to slide over both panels together and would allow me to finish the joint with a single wing screw without separate washers. For what it's worth, in this case I'm looking for an M6 nut, stainless material, and 6-8mm thickness of the two panels together)

Does this widget exist and have a name? If so, who might supply such a widget at 2000pcs / year?

Thanks in advance,

David

 

[hydtools]

Get a u-nut for twice thickness of one panel and assemble it over both panel.

Ted

 

[geesamand]

That thought occurred to me but I have not yet found a u-nut that fits over the whole 8mm thickness. With M6 size hardware, U-nuts typically stop at 4mm thickness.

Going along that line of thinking, it could be done with a custom u-nut.

David

 

[MikeHalloran]

A U-nut over the edge of two panels with a wing screw through two mating holes is not functionally different from a cable tie over the same panels.


Mike Halloran
Pembroke Pines, FL, USA

 

[geesamand]

Mike,

That is an interesting idea. However I don't see a cable tie as functionally same, at least in this case.

A cable tie might keep the panels together but it will not hold preload and it will be more prone to wear/tearing if the plastic panels flex. In my case we are exposed to outdoor environment where heavy winds are present and I need a rugged connection.

An additional factor is the cover must be readily removable in the field for maintenance and the fastener is expected to be re-useable. Cable ties do not meet that expectation and would have a poor appearance.

 

[MikeHalloran]

Well, they're still universally ugly and the preload is limited, but cable ties are available in releasable reusable and UV-resistant versions.



Mike Halloran
Pembroke Pines, FL, USA

 

[geesamand]

I'm glad you put that idea out there because in the field our customers often replace this hardware (after warranty) and our outside sales guys could make the cable-tie suggestion.

David

 

[rb1957]

we use anchor nuts (eg AN366), rivet a nut retainer to the back-face of the plate.

you can also use adhesive nut-plates, "Click bond", but they can be fussy about surface treatments.

 

[btrueblood]

PEM makes broaching-type captive nuts that can be installed in fiberglass and polycarbonate panels; you never mentioned what type of plastic you have.

 

[rb1957]

is riveting out of the question ?

 

[badservo]

Something like this?

http://shop.stafast.com/catalog/standard-short-prong,645.htm

 

[geesamand]

My material is ABS or ABS with static-dissipating Acyrlic coating, 2.5-4mm thick per sheet. It may be tough enough to consider a broaching-type nut as long as it has a nice wide washer profile to prevent it from pulling through, and that it won't fall out or get knocked out after it's been disassembled. That's another good idea, thanks.

rb1957: yes, I am not considering it for reasons of reassembly and the fact that the dirty side of the rivet will remain exposed to operators.

badservo: A t-nut could work but my gut tells me those prongs might be too severe. It warrants a test however, and a design with mild enough prong engagement could work nicely.

 

[KENAT]

I was thinking same as btrue, check out PEM and similar suppliers. Or you may be able to bond a threaded insert into the ABS.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[btrueblood]

Kenat's suggestion of bonded inserts gives me another idea, since it's ABS: bond a washer-shaped piece of ABS to the nut side sheet, to build up the thickness of that sheet to better support a heat-staked/ultrasonic-staked/bonded or similar insert designed for molded plastics.

 

[telecomguy]

Was the idea of a recess for the U-nut material thickness abandoned because these are existing parts? That's probably where I'd start if I had an option of adding it to the tooling.

Or you might look at rack nuts.

http://www.google.com/search?hl=en&...pw.r_qf.&fp=1dbff8ba06d7c813&biw=1029&bih=915

 

[KENAT]

Took a quick look in my PEM catalogue that I had open for another project but your panel thickness is to thin by the looks of it.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[KENAT]

... Unless you use btrues suggestion sorry.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[geesamand]

I spoke with PEM today and given the thickness and that ABS has such limited cold flow, and the fact that I would prefer to allow these fasteners to fit existing covers, they recommended one of their self-broaching inserts designed for PCB applications. I'll have my samples very shortly.

 

[keluonuosi]

hi geesamand,

Maybe you can try the "Rivets Screw"

http://www.anixtercomponents.com/

;or Similar ITW parts。