Crunch nuts

[H3Jim]

Thought everyne might like to see a fastener I have used a lot of.

When I was installing my microwave, hanging directly from the ceiling, and installing the cabinet above the driver, I needed to  have a fastener that was very strong and could hold a lot of weight.  My ceiling structure is all square tube, and while I can drill into it, I could not get above to put a nut.  Alll I could do was to use some big @$# sheet metal screws, but that was not satisfying to me.  I spent a lot of time looking at various fastener places, and maybe I was just not looknig in the right places, but I never did find one as strong as Prevost uses.  Prevost uses a very strong 5/16" blind fastener, so I bought a bunch from them.  They were kind of pricey, but in the big picture, it wasn't that much $.

Attached is a picture and the mickey mouse install tool I cobbled together.  Hey it worked well.

The tool, home made, works really well.  The only thing that actually threads on the bolt is the nut itself, everything else is a spacer.  The regular nut you see is 3/8, too large for the threads, its there to make contact with the crunch nut and help keep it from turning.  I put a wrench on that nut to insure it doesn't turn.  I drilled 1/2 hole in the square beams, pushed these in and tightend them down.  I can hang and bounce  my whole 200 + lbs off just one.  Very solid.

[kyle4501]

Nice trick with the oversized nut & star washer to keep insert from spinning. I've used 'em before, good stuff. 

The only thing better than your tool would be a hydraulic installer, but those are spendy. 

[Jeremy]

You can I believe get threaded adaptors to enable you to close up rivnuts using a regular rivet gun (or at least a 'good' rivet gun - not a $5 hardware store job). There is also a version of the same type of fastening where the 'cylinder' body is made of rubber rather than deformable metal. They probably cannot hold as much weight, but are still pretty soild. Their cheif advantage (or disadvantage, depending on your application) is that they can be removed - once the bolt is unthreaded from the nut, the rubber straightens out and the whole thing drops back out of the hole.

Jeremy

[H3Jim]

I use those rubber ones on the outside, going through the fiberglass to hold on trim pieces and lic plates etc.  For the more structural uses, I don't plan on ever taking them out, and the extra weight holding is great.  Especially for a cabinet over the driver - don't want to be bonked in the head, and the microwave - I sure want it to stay put.  From these two responses, it seems that both of you are familiar with these types of fasteners, and I must just have not been looking in the correct places for them.

[kyle4501]

I usually can't find them when I need them. 

If I remember right, the last ones I used were called 'rivnuts'

Just seeing the name 'crunch nuts' makes me think of an accident I'd rather not have.   

[ChuckMC8]

when I read this topic, I thought it was gonna be something else!

[H3Jim]

Sorry about the name, that's what the service manager at Prevost called them.  He said he knew that it wasn't right, but it was all he knew.

like a bicycle accident....

[brojcol]

Hey, Crunch nuts are great for breakfast, I love em.  But I prefer whole milk to skim.