drill & tap frame or rivnut/nutsert?

Discussion in '80-Series Tech' started by clownmidget, Jul 14, 2005.

  1. clownmidget

    clownmidget

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    I need/want a couple more tapped holes on the bottom of the frame rail in the same diameter as whats already there, I think that must be 10 or 12-mm. This is for a skidplate mount.

    At any rate, is it recommended to drill and tap the frame or to drill and use a rivnut/nutsert. I am impressed with the rivnuts I used for the aux tank strap mounts and for the snorkle a-pillar mount so I think they would be up to the task. I've never looked but are the existing threaded holes using welded/captured nuts on the inside of the frame rail? Thanks.

    Mike
     
  2. CharlieS

    CharlieS

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    There are several captive nuts in the frame in the area of the transmission/transfer case.

    I wouldn't choose to use an aluminum riv-nut to do the job. From what I recall they are a light duty fastner best suited to attachment to thin guage metal. The frame is pretty thick.

    Yes, the exisitng holes are captive nuts. There is a reason captive steel nut are used to hold things in place on the frame.

    I would think that you'd want more "meat" to thread your fasteners into than a tapped hole in the frame would allow.

    You could weld in some more captive nuts.

    Charlie
     
  3. e9999

    e9999 You want to do what...? Moderator

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    well, if it's a skidplate, the most stress they would feel is if you scrape the plate on something. At that point, the main stress on the bolts would be a sideways shear, not a pulling down - probably. So, the threads may not be as critical for this application as for hanging down something heavy...
     
  4. CharlieS

    CharlieS

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    I guess it depends on usage.

    Might be ok for rock crawling, I don't have any experience with that. Rivnuts might be fine.

    For "expedition type" driving I suspect if a skidplate is used offroad, there are going to be some near horizontal strikes. In my opinion the fastener needs to resist shear forces.

    If it is just there for bling, then do whatever is easiest.

    On my rally car we welded captive nut into holes in the engine subframe. Worked like a charm.

    Incidentally, a little cushion is nice to have between the skid plate and body - isolates some of the harshness. I've saved some shock bushings for my skid plate project.

    If rivnuts are what you want, then use them. Time will tell.

    Charlie
     
  5. clownmidget

    clownmidget

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    My original reason for asking was to consider stresses to the frame as I'd like to avoid developing any cracks in it. I would definitely prefer to weld in steel nuts but I'm not certain I'll be able to reach them in every place I'd like.

    Thanks for the replies.

    This is my only vehicle so it has to do everything. I will use some shock bushings as that solves a bit of a small clearance issue as well. Also, I believe there are steel rivnuts that can handle an incredible amount of force (at least according to the manufacturer!) but again, just wanted to hear what experience others had.
     
  6. cruiserdan

    cruiserdan SupportingVendor Emeritus Moderator

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    I do not like the idea of drilling holes in the frame. I wouldn't mind setting steel inserts in existing holes however. I would not use those inserts for critical mounts. The steel ones I used for my subtank in 8mm had a lot of material around the threaded area and looked quite substantial. At most, each one is supporting around 60 lbs with a full tank.
     
  7. ElJefe

    ElJefe

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    If you have access to the right equipment to do the rivnuts, I would have no problem using STEEL rivnuts in place of captured nuts on the frame. We use SS rivnuts all the time offshore on our ROV's to attach things structurally to closed tubing. The only downside is the equipment to properly set an alloy M8 or M10 steel rivnut is a hydraulic monster.

    Chris
     
  8. turbocruiser

    turbocruiser SILVER Star

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    Whenever I fab skidplates I try to take the ubolt approach; over the frame in three directions seems stronger than through the metal that might only be 1/8 thick. This is the method I used on the 80 for my exhaust pipe skidplate. HTH.
     
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