Rear bumper stripped threads

Sup tw. Took off rear bumper first time in a while and I’m assuming these nuts in the backside were stripped to begin with from the dude who made the bumper because some of the bolts had a extremely difficult time coming out and when I went to re install it it appears that the welded nuts are stripped. Half of them are okay half don’t want to thread properly. What’s the best way to go about fixing this? Got a couple ideas in mind but would like to hear from you guys if I can keep using the OEM bolts that would be best. Circled the stripped threads and other picture shows how far the bolts r going in. Thanks

 

Anyone know the part number for those bolts as well?

 

I'd try running a tap thru the nuts and see if the threads clean up so a bolt properly fits

 

Exactly what @Clearwater Bill said take a tap and trace the threads and buy you a new set of OEM bolts from your local dealer.

 

This^^^^^^^^^^^

 

Worst case scenario, drill out the nuts and through bolt it with new hardware (new nut and bolt). If you want to be extra, you can even grind off the existing captured nut.

 

This is a good solution that I've used. Drill them out for 1/2" grade 8 bolts (2" length) and leave the captured nut in place.

Drilling out to size is a PITA but not overly complicated. Buy an extra drill bit or two unless you have a way to re-sharpen bits.

 

Chase the threads with a tap, as suggested. The nuts may have distorted when welded, heat does that. You may want to clean up the threads on the bolts with a die also.

edit: Weld spatter can damage threads also.

 

Are you saying to drill out the nut and re thread it for a 1/2” bolt or putting your own grade 8 nut on top of the welded nut? Would you mind attaching a photo of what you did? Also were your threads stripped or did you just want to use grade 8 hardware for the bumper?

 

Thanks for all the replies. Had to get a specific size for the tap since an 12x1.25 isn’t in most tap and die sets. Going to work on it when the bolts come in from toyota. I believe that the dude who made my bumper made the mounting hole tolerance a bit to tight and forced the bolts in and stripped the threads or the frame or bumper was bent slightly and I stripped them backing them out. Going to also take a 5/8” drill bit and make those holes a bit larger on the bumper but enough to still get bite from the bolt and washer.

 

On the assembly line, most frame and body bolts aren't started by hand. The workers jam them in with calibrated power tools. The bolts have a piloted tip to reduce the likelihood of cross-threading, but there's no guarantee.

Clean out the threads with a thread chaser. I had good luck with this set:

$28 Angchun 15PCS Metric Thread Chaser Set, Thread Repair kit with 7 Taps Thread Chaser Set Universal Metric Thread Restorer Kit with 7 Dies and 1 Thread File Rethreading Kit Universal Rethreading Tool

https://www.amazon.com/Angchun-Metric-Universal-Restorer-Rethreading/dp/B0BNX7S4LD/

 

Try to tap the existing hole as you've mentioned.. but if that doesn't work or the final threads are shait then my proposal is a strong alternative.

I too had a cross-threaded stock bolt/nut location and decided to replace them all. I drilled out the hole and existing nut to 1/2". Fuuuu trying to tap the existing nut because drilling/heat has hardened it.

Use a 1/2" bolt and 1/2" flat washer.. then on the oem nut side use another 1/2" washer, 1/2" lock washer and 1/2" nut.. all grade 5 or better. I did this at 10 locations as I wanted all the hardware to match attaching my custom bumper. Torque to 95 ft lbs.