Questions about rivnuts in aluminum
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    Default Questions about rivnuts in aluminum

    Hi folks, longtime reader, first-time caller. I'm building something in 1/8" x 1" 6061 Al square tubing, and I'm planning on using rivnuts. (sorry, can't provide much more in the way of detail)

    1. How do you choose a particular style of rivnut? I'm planning on using ribbed aluminum (it had fewer issues with twisting than steel rivnuts when I tried both, and seemed less likely to deform the aluminum tubing around the hole and come loose), but my coworker recommended using steel, because it's stronger the threads are less likely to strip (though this won't likely be disassembled once assembled). Anyone have experience using Rivnuts in aluminum?

    There won't be much force on the bolts, 50 lb at most, with the spots seeing the highest force doubled-up.

    2. What's your experience using hand-set rivnuts (with the lever-action tool) vs something done in a shop (with a pneumatic setter?)

    Thanks in advance!

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    Proper hole preparation, correct setting forces, and using a quality rivnut should give trouble-free life. Amusingly, I just watched a documentary on the construction of Aston Martin road cars, and there's a five second clip of a worker installing some M4 or M5 rivnuts in a chassis panel.

    Al on Al is fine, especially at low forces and if the screws aren't meant to be removed. But if used outside or in a corrosive environment, then you might have some galvanic issues if using steel or stainless fasteners.

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    A thought

    You might want to look at Flowdrilling Home page - Flowdrill

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    When I worked on the Plymouth Prowler project we were putting dozens of steel rivnuts in the extrusions for attachment points. They are well proven, and for automotive and military applications you almost always want steel threads if you can get them. If it's going to take any real force or loading/unloading cycles, or if it's in any sort of application where the threads failing could cause personal harm, then go steel. If you're hanging potted plants, then aluminum rivnuts are a great way to put a bolt in tubing.

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    I have put many steel rivnuts in aluminum and they work very well. All of the ones I have used were with the non pneumatic variety. As Milland stated hole prep is important. I would say hole size since you don't have to do much to prep the hole but it has to be the proper size. Any slop and the rivnut is likely going to spin on you.

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    I do lots of rivnuts.

    The style depends on the application. The AET style set by separating the body of the rivnut into 2 halves. The bottom conical section is pulled up into the top cylindrical section, expanding it to the hole. So it grips on the diameter, but it does not create a flange. Hole size is critical. McMaster calles these "low profile" style. They are good for installing in round tubes where you cannot create a flat flange on the underside. You can also use them in blind holes.

    AEK/AEL style set by first expanding the ribbed section to fill the hole, then as it continues to pull up, a flange is created on the bottom side. The material is sandwiched between the head of the rivnut and the flange on the bottom, with the ribs gripping the material. McMaster calls these "twist resistant" style. They are less fussy about the hole size, and .003" or .004" over won't kill you.

    AEK and AEL styles can take more torque than AET styles. The difference between AEL and AEK is the diameter of the head, AEL being the larger of the 2. They both use the same hole size.

    I don't like the lever type setting tools. They are tricky to get set properly, and any variation in the material thickness and you will have problems. Better to just set it by hand with a cap screw or buy the wrench setting tool from McMaster.

    McMaster-Carr

    Set the rivnut with an allen wrench, then follow with a torque wrench to the proper torque for the fastener size you are using.

    Properly set, a steel rivnut in aluminum will take the full torque spec of the fastener and beyond. I have tested my M5's (AEKS-580-3.3) to over 100 in/lbs.

    The rivnuts sold by McMaster are Marson brand AEL style. I don't like these and don't use them. I found they did not pull up consistently. I normally use Atlas rivnuts from Bossard in the AEK style.

    Pay attention to the grip range, and try to be in the middle of the range for best results.

    Finally, if you have to remove one, don't attempt to drill it out. As soon as you have the head cut off, the body will start spinning and oversize your hole. The correct way is to machine the head off and thread a fastener into the body and drive it through to the backside. This will leave the hole intact for another try. If the rivnut has spun in the hole, you need to grab the bottom side with a vise grip or channel-locks to keep it from spinning when you machine the head away.

    If I was setting 1/4"-20 rivnuts in 1/8" aluminum, I would select AEKS-420-165. That's a cad plated steel rivnut with a grip range of .027" to .165". I'd make the hole with a 25/64" drill, and set the rivnut to about 70 in/lbs.

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    Check out Astro tools drill rivnut setter. I’ve had one for about a year. Beats the hell out of doing it by hand. Not affiliated, just a cool tool.

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    Quote Originally Posted by Limy Sami View Post
    A thought

    You might want to look at Flowdrilling Home page - Flowdrill

    Had one of their samples in my toolbox.




    flowdrill1.jpg flow-drill-2.jpg

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