Cross nuts and Jack nuts?

[Iceni John]

Which are stronger?   I was planning on using 1/4"-20 Jack nuts for attaching my upper cabinets to the roof ribs, but now I see Cross nuts as an alternative.   I haven't found any tensile strength info for the latter;  a 1/4" Jack nut has over 800 lbf strength according to Stanley POP's website, which should be plenty with four per cabinet.   Cross nuts seem to have more metal, so their four splayed-out legs seem slightly wider than Jack nuts' legs.   Or is there anything better for making permanent threads for a blind hole in a box-section rib made of 3/32"-thick 90,000 PSI steel?   Rivnuts, wellnuts and toggle bolts obviously are not realistic options!

Thanks, John

[luvrbus]

We used the Sammy's to hang cabinets in commercial buildings,they are sorta of hard to work with till you get the hang of it then when right they are forever 

[Iceni John]

The Sammy X-Press anchor looks like a beefed-up version of a Jack nut, and it has 1300 lbf pullout strength which is good.   I don't mind their $8 cost each, but $330 to buy the special tool that I'll need to use only eight times is too much!   It looks like my Jack nut tool won't work right for the X-Press anchor  -  I assume its draw-in force is a lot higher than a Jack nut's.   I like that the X-Press has a longer threaded section than the Jack nut, but unless I can A) borrow the tool for cheap, and B) buy only eight individual anchors (not a whole case of them), I think it may not work for me.   Thanks anyway for the recommendation  -  I just have this neurotic fear of something coming loose, so I'd rather overbuild!

I also thought about beefing up a Jack nut by soldering a plain nut onto its end, then I wouldn't be relying on just the Jack nut's own imprecise thread.

Thanks, John

[bevans6]

I've never used anything other than Rivnuts for things like that, where I wanted a high quality reusable thread in a blind cross section.  I don't understand why you think they are not a realistic option?  The way I use them I don't need a special tool to install them.  For upper cabinets, frankly I just used self tapping screws.

Brian

[Oonrahnjay]

I've never used anything other than Rivnuts for things like that, where I wanted a high quality reusable thread in a blind cross section.  I don't understand why you think they are not a realistic option?  The way I use them I don't need a special tool to install them.  For upper cabinets, frankly I just used self tapping screws.

Brian 

    The seats in my bus (original transit seats) were held in place by two 1/4" machine screws (washers, and nuts) to a flange along the body side and two self tapping wood screws to the plywood floor.  AFAIK, those seats never moved, the self tappers never came loose, and they were one pure bear to get out (DAMHIK).   Having dealt with those, I have a lot of trust and respect for self tappers.

[Iceni John]

I've never used anything other than Rivnuts for things like that, where I wanted a high quality reusable thread in a blind cross section.  I don't understand why you think they are not a realistic option?  The way I use them I don't need a special tool to install them.  For upper cabinets, frankly I just used self tapping screws.

Brian

The reason I'm leery about using Rivnuts is that I've had experience of them coming loose in aluminum tubing, essentially making it impossible to tighten bolts into them.   Maybe this was because they were against a curved surface, maybe they just weren't installed right, who knows?   I'm also hesitant about using self-tapping screws simply because the roof ribs' steel is so damn hard  -  when drilling through Crown's structural members it feels like drilling through hard stainless steel, and the bits dull just as quickly!   This is why I'm thinking more along the lines of a thread-insert type of fastener or anchor.

John   

[Iceni John]

I did some destructive testing (always the most fun sort) this evening with different length 1/4"-20 Jack Nuts.   They're all crap!   Either their wimpy emasculated threads tear out of the end "nut" section, or the entire end separates from the rest of it.   Either way, they just don't work for heavier loads at all.   I think the smaller 10-24 size would be adequate for light loads, but there's no way the 1/4"-20 have anything close to their claimed 800+ lbf strength.   So, cross them off my list.   I'll give Rivnuts another try, but if they don't work well enough then it's back to the drawing board for my overhead cabinets.

I also tested a few stainless self-tapping screws into some structural ribs.   I had to drill their holes much larger than their minor diameter, and I don't think they're biting very much into the steel  -  the threads they make seem very shallow to me.   I think I need to try some better quality hardened screws instead.   Nothing's easy!

John