I have an Aero lower that has the threaded detent spring hole. I have tried several times to get the spring in the hole, no luck.
What is the secret?
I have seen 2 option. 1, cut the spring which i do not recommend at all. 2, fight with it til you get it in, for the second method buy lots of spare 4-40 set screws. Me personally, i launched 4 or 5 set screws and finally gave up and installed the spring normally.
The problem I am having is due to the threads in the hole, I can’t even get the spring into the hole.
Not to insult you, but are you sure you aren’t using the safety detent spring? If its the correct spring for the takedown pin detent, then the hole may be slightly out of spec or the spring is out of spec. Try using several different springs. If that doesn’t work, call aero
I asked for help, you gave me a suggestion. Not any where close to being an insult. Also you were 100% correct. I swamped the springs and all is good.
I need stronger reading glasses.
Thank you so very much
Glad you got it sorted.
I see you corrected it but I always snip 1/8"-1/4" off the spring and install the snipped end toward the set screw. You can obviously force the spring in but I feel like it puts excessive pressure on the take down pin; IMHO of course.
It was such a stupid mistake, and it drove me crazy trying to figure it out.
But I think it is good for all of us to every once in a while feel like an idiot.
Indeed.
I’ve done some boneheaded things that leave me scratching my head sometimes.
Keeps us humble, good reminder that we ALL make mistakes every now and again. 
Get safety glasses with magnifiers in them.
Had a friend recommend those to me and it was within a week or 2 of picking a pair up I watched a spring loaded part hit the lens instead of my eyeball.
Seconded. My everyday Rx glasses are safety-rated polycarbonate, and they’ve taken a few detents that meant themselves for my eyeballs over the years.
Safety glasses saved my eyes from an hk91 firing pin that gouged a groove in the polycarbonate. I wouldn’t have an eyeball if I hadn’t been wearing glasses.
That is why this place can be so great.
I never would have thought about safety glass readers
Or consider pairing your safety glasses with an Optivisor–those were a big help back in my scale modeler days. Oh, to have the hands I did when I was a teenager again, before the damn tremors…