Fix screw holes in wheel center cap ?

[7E-Bodies]

@Racer57 I hope I caught you in time. LOL

I dug back through my Amazon history and found the link. $13 US!
https://www.amazon.com/gp/product/B09WN55FJJ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

[mtull]

@mtull the ONE NOS center cap I was able to obtain had zero threads. I am under the belief that the factory bolt was machined in such a way as to cut it's own threads. That when combined with the less than desired pot metal (my term), these threads were made to fail. I am absolutely certain I did the right thing by drilling out the old threads slightly and inserting 1/4" helicoils into a freshly tapped 5/16 thread. The coils lock down incredibly.

Exactly the info I was looking for, thank you

[YellowThumper]

While were on the topic of center cap screw holes, is it best practice to tap the holes if the center cap has never been used or do they come already tapped?

Yes the screws are self tapping. So in theory (because factory did) you can also.
However, I would personally tap them first. If original they are 50+ tears old now. And may be more brittle.
If aftermarket I would not trust the hols to be correct sizes for the self tappers.
Lastly, using a tap would be vastly sharper for cutting threads cleanly. Less chance of pushout.

[RJChallenger]

I would before taping the holes check the threads on the bolt. I do not believe they are either NF or NC. National fine thread or National coarse thread meaning a regular nut will not thread on easily. The tap may actually remove material from where the self taping screws would want to cut its thread The self taping screws have a cut line down the length of thread to clean out the cut material as it cuts its thread. I would hate to ruin good holes on the center cap, but as @ 7E-Bodies said you can always use a heli-coil as a last resort

[RacerX]

@mtull the ONE NOS center cap I was able to obtain had zero threads. I am under the belief that the factory bolt was machined in such a way as to cut it's own threads. That when combined with the less than desired pot metal (my term), these threads were made to fail. I am absolutely certain I did the right thing by drilling out the old threads slightly and inserting 1/4" helicoils into a freshly tapped 5/16 thread. The coils lock down incredibly.

Pretty sure this is the case on the way they were made...   

I have had some with no threads also, and if you look
at the screws they are self-tappers

[71GranCoupe]

If you are concerned about them working lose, possibly a small dab of lock tight on the flat shoulder of the bolt to mate up with the wheel. Just a thought.

[70_440-6Cuda]

For self tappers I have always thread them into the uncut hole slowly before installing, and back them out often to clear out the material as others have suggested.  I find one of the biggest issues is the cut material binding up while you are tapping.  As always, patience, especially on 50 yo parts

[YellowThumper]

Bolts are 1/4-20 for the threads.
Yes as mentioned self tapping.