PEM nuts, or something like that for sheet metal

WobblyHand

WobblyHand

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I want to use something like a PEM nut to tie down a stepper motor controller. Issue is the aluminum Bud box I have isn't that thick. Mic says it is 0.048" thick. Thought I'd put the flange of the insert on the outside of the box and set it with my arbor press. The controller is not that heavy. Using M5 screws. The controller would be inside the box with the M5 screws pulling the controller towards the sheet metal.

Right now, this is what I selected. https://www.mcmaster.com/95185A630/ Are there better choices for this application?

Trying to avoid loose nuts! Too many of them running around the shop as is. :grin:
 
heathautosports said:
Hi
Did you have a look at rivet nuts, available in flanged or countersink.
We use them all the time.
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I looked at them. They look good, but you need the tool to set them, which I don't have. The hand tool is $35. (For that one size.) If I had a drawing of the tool, maybe I could make it. McMaster only shows the exterior view. Can't quite figure it out from just that picture.

If you could prevent the rivet nut from rotating, then tightening the screw should cause the rivet to collapse, tightening it to the sheet metal. Would be handy if I was doing a lot of sheet metal stuff.
 
I made a tool for fitting them, turned up the mandrel out of a bit of hex bar and drilled the centre hole for the correct thread bolt. works every time. If i remember I'll photograph it tomorrow.
 
You can get UNC or metric hank bushes, also in stainless from eBay. There are types that have serrated rivet grips, but if you make the hole a slightly tight fit, then tightening a bolt onto it secures it permanently. This would be to mount the hank nut onto sheet metal. I found using A2 stainless steel types excellent for mounting to aluminium. In thicker aluminum, I use stainless helicoils, instead of trying to tap a thread into the soft aluminium.

Steel against aluminium has that dissimilar metal corrosion potential, making a white oxide that seizes to the bolt forever. The interface between the aluminium and a hank bush becomes permanent, regardless the oxide, and the stainless threads in it will never seize up onto the bolts.
 
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Hank nut is cool to learn about, thanks.

The issue with any nut type fitting for this is the external appearance, in that it will depend on screw length for neatness.

I’d probably use female stand-offs and flat head screws from the outside.
 
graham-xrf said:
You can get UNC or metric hank bushes, also in stainless from eBay. There are types that have serrated rivet grips, but if you make the hold a slightly tight fit, then tightening a bolt onto it secures it permanently. This would be to mount the hank nut onto sheet metal. I found using A2 stainless steel types excellent for mounting to aluminium. In thicker aluminum, I use stainless helicoils, instead of trying to tap a thread into the soft aluminium.

Steel against aluminium has that dissimilar metal corrosion potential, making a white oxide that seizes to the bolt forever. The interface between the aluminium and a hank bush becomes permanent, regardless the oxide, and the stainless threads in it will never seize up onto the bolts.
Click to expand...
This is only 1.25mm thick aluminum. Nothing to thread really.

Was wondering how the rivet set tool held the rivet from rotating. It seems that all one might need is a hex with a through hole tapped to the right size and a counterbore to let some of the rivet to drop in place. Then hold the hex with a wrench and screw in the screw until the rivet is set. Hmm, doesn't sound that hard. I'll practice on a few before trying on my box though!
 
Buying a tool to set rivet nuts isn’t all that expensive if you may use them a few times. They can be handy. Like this: https://a.co/d/i2oRezG
 
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