Hey there everyone,
I was installing a new MIAD grip onto one of my BCM lowers the other day (thanks Grant!), and it got insanely tight only half way through the installation process. It eventually froze, and I feared that I cross-threaded the threads. After removing everything, the threads turned out to be fine and it was just Magpul's cement-like compound pre-applied to the threads that jammed everything up (holy crap, Magpul, that stuff needs to go). I removed their compound, applied some blue Loctite, installed the grip until the screw was snug against the plastic, and went a quarter turn further.
This got me thinking that there's got to be a better, more precise way to do this to ensure one doesn't strip the threads. Turns out there isn't a spec that I could find other than a mention of 35 in-lb on here in in 2006. Knowing that there are general specs out there for all materials and threads, I started searching to see what I could find. Found these sources:
http://hydraulicspneumatics.tpub.com...338-12P_67.htm
http://yetmans.mb.ca/kohler/page3/page3.html
www.ligo.caltech.edu/docs/T/T970244-00.pdf
It looks like the maximum torque value for 1/4-28 threads at a minimum of 0.5" depth is between 55 in-lbs. and 120 in-lbs for aluminum. Obviously it depends on the type of aluminum, but overall, it seems like you don't want to exceed 55 in-lbs. For those of you with more experience than I do, does that sound right?
This also leads me to think, how the hell do people strip their grip screw threads in the lower!? 55 in-lbs with a flathead seems like an absolutely insane amount of torque. I was scared I would strip my threads at snug+a quarter turn, but man, that's a lot. I can't even see hitting that without socketing a wrench to the driver. Are people putting their lower in a vice and putting a gorilla grip on their screw driver?
...but I don't have as much experience as you guys. What do you think? Don't exceed 55 in-lbs on your grip screw? And what would that "feel like"?


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