PEM nuts

[g zilla]

How good do these work do you need an instalation tool. I was looking at them online an found 100s dont know which ones to get

 

[Worsaer]

They work great in fiberglass, and in Blue Tube. What do you want to use them for? That may indicate which ones you want to purchase.

No installation tool necessary, but brad-point drill bits help by cutting very clean, round holes for them.

 

[hball55]

Go to Missile Works and look at the fasteners. These are the ones I use to secure my av bays to the payload section.

 

[Bat-mite]

I use them for rail buttons. I apply a mound of epoxy strengthened with CF over the back end. If you do it this way, dip the threaded end of the screw in Vaseline and epoxy over it. Then you can unscrew it later and remove the button if you want.

 

[markkoelsch]

Pem nuts- love the things. I use the broaching nuts, and have never use a tool other than a screw, washer, and screw drivers To insert them.

Pay close attention to the recommended drill size.

 

[hball55]

Pem nuts- love the things. I use the broaching nuts, and have never use a tool other than a screw, washer, and screw drivers To insert them.

Pay close attention to the recommended drill size.

I use a drill guide to size the holes for the nut and drop down 1/64. I then tighten the screw as tight as I can to set the nut in the hole and back the nut with epoxy. I have had a nut come loose inside the av bay a couple times before I started using epoxy to back the nut. It was a bear getting the nut to seat well enough to back the screw out, so I started using epoxy.

 

[ChrisAttebery]

Make sure you get the type for soft metals and plastics. They are also used for circuit boards. Buy the matching drill bit at the same time.

I use an Allen wrench a short cap head screw and a stack of washers to pull them into the tube wall.

 

[soopirV]

Make sure you get the type for soft metals and plastics. They are also used for circuit boards. Buy the matching drill bit at the same time.

I use an Allen wrench a short cap head screw and a stack of washers to pull them into the tube wall.

Could you provide more detail on this? I tried using some tabbed weldnuts inside my 4" avbay to accept #6 machine screws, but the epoxy didn't bond very well with the metal. Penn Engineering has this video on their site, so I'm guessing you're using the washers and screw in place of the anvil and press? https://www.pemnet.com/design_info/animation-library/pennengineering-animation-library-nuts/pem-self-clinching-nuts/

Last question- These are intended for flat panels, but it seems they mount fine to curved surfaces as well? Any special precautions used?

Thanks!
Dave

 

[ChrisAttebery]

Dave,

I use the tin plated KF2 type:
https://catalog.pemnet.com/viewitems/nuts-broaching-types-kf2-kfs2/broaching-nuts-types-kf2-kfs2-unified

I drill the hole with the recommended drill size. Don't try to use whatever you have in your drawer. I use my fingertip or a dowel with double sided tape to hold it against the inside of the hole. Thread a short cap head screw with a couple thick washers into the nut. Then carefully turn the screw until the nut is started in the hole. Then use an Allen wrench to crank the screw until the nut bottoms out in the tubing or against the washers. Once they are in they won't come back out.

 

[soopirV]

Dave,

I use the tin plated KF2 type:
https://catalog.pemnet.com/viewitems/nuts-broaching-types-kf2-kfs2/broaching-nuts-types-kf2-kfs2-unified

I drill the hole with the recommended drill size. Don't try to use whatever you have in your drawer. I use my fingertip or a dowel with double sided tape to hold it against the inside of the hole. Thread a short cap head screw with a couple thick washers into the nut. Then carefully turn the screw until the nut is started in the hole. Then use an Allen wrench to crank the screw until the nut bottoms out in the tubing or against the washers. Once they are in they won't come back out.

This is great info! Thanks! What material have you used this on? I'm sure fiberglass works well (given it's for use on PCB), but have you had any luck with CA-soaked cardboard? I can glass the inner surface of my problem spot I hope to employ this on, but am not looking forward to it, if it's not required.

 

[ChrisAttebery]

I've only used them on fiberglass. I wouldn't use them on anything softer.

 

[Handeman]

For Loc tubing, I just shape a piece of oak about 3/4" wide and 1" long and 1/4" thick so it fits flush to the ID of the tube. I then shape the ends so there are no sharp edges for recover items to catch on. Glue that to the inside and use 3/8" to 1/2" long SST #6 sheet metal screws. Drill your hole, put a little soap on the screw and screw it in to set the threads. Once the threads are set, you can grind the tip of the screw down so it stays flush with the top of the wood if it's in the BT with recovery gear. Shouldn't be needed if it's in the av-bay.

The screw heads do protrude into the air stream, but I've used this method on a 4" rocket I built in 2009 and has 36 flights on it. It's held up great so far, even Mach speeds, drogue only landings, and various other minor mishaps. YMMV

 

[rharshberger]

For Loc tubing, I just shape a piece of oak about 3/4" wide and 1" long and 1/4" thick so it fits flush to the ID of the tube. I then shape the ends so there are no sharp edges for recover items to catch on. Glue that to the inside and use 3/8" to 1/2" long SST #6 sheet metal screws. Drill your hole, put a little soap on the screw and screw it in to set the threads. Once the threads are set, you can grind the tip of the screw down so it stays flush with the top of the wood if it's in the BT with recovery gear. Shouldn't be needed if it's in the av-bay.

The screw heads do protrude into the air stream, but I've used this method on a 4" rocket I built in 2009 and has 36 flights on it. It's held up great so far, even Mach speeds, drogue only landings, and various other minor mishaps. YMMV

Or you can put a threaded insert into the oak block.

 

[Banzai88]

Good info here.

 

[Graduator]

For any tubing other than fiberglass, I just cut a small square out of G10. Press the PEM nut into the G10 and epoxy that to the inside of the coupler.

 

[ChrisAttebery]

Check out the big brain on Graduator. I'm stealing that idea.

 

[soopirV]

For any tubing other than fiberglass, I just cut a small square out of G10. Press the PEM nut into the G10 and epoxy that to the inside of the coupler.

Check out the big brain on Graduator. I'm stealing that idea.[/]

Ditto! Solved my problem without me having to try to glass an inner radius (probably still a good skill to have though).

 

[markkoelsch]

Glass interior radius. Have glass cut and epoxy ready. Wet glass with epoxy and insert rolling it flat. Insert long balloon into tube, inflate, and tie off. When epoxy sets pop balloon.

 

[soopirV]

Glass interior radius. Have glass cut and epoxy ready. Wet glass with epoxy and insert rolling it flat. Insert long balloon into tube, inflate, and tie off. When epoxy sets pop balloon.

Interesting- I've only moved wet glass using John Coker's technique of wetting it out on butcher's paper, and using the paper as a backing to work the wet glass into the tube. Are you able to move the glass wet by hand? Understand that it's a smaller piece, but still seems like herding cats- any tricks? Nice idea about the balloon, makes perfect sense.