How to fabricate and install Heavy Duty Threaded Inserts

Recently when channeling my Ford Model A I wanted to use Grade 8 fasteners for all of the body mounts instead of just tapping threads into the frame or inserting rivnuts that could fail over time. First of all the 1/4″ wall of the tubing wasn’t really thick enough to give sufficient threads to hold the weight and twist of the body from normal driving. We came up with a slick solution and figured we’d share.

I started by threading a batch of Grade 8 nuts onto a carriage bolt and locking them all together.

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I then mounted the bolt into the lathe and cut off the hex portion of each nut leaving us with perfectly round grade 8 threaded inserts. The nuts were cut down just a hair bigger than 1/2″ so they would be a press fit into a 1/2″ drilled hole.

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I then counter sunk each hole and threaded a bolt into each insert so I could adjust them so they were straight in the holes. I used the TIG 200 to carefully lay a weld puddle on the edge of the threaded insert melting it to the frame. You must take your time here and be very precise because a rogue dab of filler rod could go over the edge of the threaded insert and make your life hell when it comes time to thread a bolt back into the insert!

 

 

 

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Hopefully you can use this method to put some clean, strong threaded inserts in your next project.

-Matt/EW

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54 thoughts on How to fabricate and install Heavy Duty Threaded Inserts

  • what do you do with the raised bead, grind it smooth and you have nothing. I would run a 45 degree countersink in the hole before placing insert in it that way you have more weld grip and you can grind it flat

  • If you reread the article and look at the pictures you will see I put a bevel in the frame to do just that. The weld bead was flush with almost no sanding needed.

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