colin00

Guys and gals of S2Ki, I've stripped the hole in which my seat belt bolt gets driven into.. pretty bad.

I was installing my Recaro SPG on Sunday night, and with a load of confidence, I blindly stuck my impact driver in, and drove the bolt in. Before I knew it.. *tchuk tchuk tchuk thcuk*. It was 1/4 of the way in, but already fully tightened - crap.

I've done my research, and used this forum's search function, and came to the conclusion that the thread pitch is a 7/16-20 UNF thread, which is apparently the NVMSS's requirement that it be that thread.

Upon trying to rethread my stripped bolt with a tap+die set I got overnighted, I noticed it wasn't the same thread pitch. I've tried another couple of bolts I got from the junkyard, and it wouldn't thread on, either.

If this won't thread on to the bolt and chase the threads cleanly, presumeably on other 7/16-20 bolts, i cant see the tap working in my favor when I try to rethread the hole on the car.

Am I doing something wrong here? Can anyone else chime in on this?

Any help is appreciated. Thanks, yall.

Billman250

I know that seat bolt threaded hole is the only SAE thread in the whole car.

Slowcrash_101

All aerospace devices are fastened in SAE. It's a plane thing. Seatbelts are technically classified as aerospace devices, as they're supposed to keep you in the car in case it goes flying, or some sort of engineer logic.

colin00

So I am ABSOLUTELY safe to assume that was an appropriate purchase to retap that mounting hole? I have an MY05, by the way. I've seen your thread and multiple others where the belt mounts on to the rail on the 06/07+.

Like I said, I've sourced some similarly sized seat belt bolts from various Hondas at a junkyard, and the tap does not run cleanly through them, which makes me worried.
I will say though, one bolt I sourced from an Accord (that mounts the pivoting mechanism on the B-pillars) isn't clean, but I can run the die through it with some force, and it doesn't seem like its making new threads.

I'm not the most mechanically inclined person out there, but when it comes to repairing dumb mistakes that I've made due to carelessness, my brain stops operating. I'm just doing my absolute best to not butcher the only thing chucking me into the windshield,

Username checks out, I appreciate the input.

FWIW, I was involved with Formula SAE my last three years of undergrad, and we used something dumb like a 7/8-16 for our harnesses, but didn't realize it was an aerospace product.



Thank you, gentlemen, I guess I'll go ahead and try my luck again tomorrow.

Billman250

06-09, Drivers side still has the threaded hole in the body for the seat belt.
06-09, Passenger sIde has the seat belt bolted to the seat itself

I can check the thread later today but I think you are correct

Billman250

Worse case scenario, retap the hole to 12mm. It is slightly larger than 7/16”. 1/2” would be too much.

Mr.Matchbox

In a metric car, it is also done as safety measure to avoid that some clueless hobby mechanics replace this screws with soft 4.4 grade from the DIY shop or whatever they will have laying around in the Garage.. that just will snap in a accident.

Car Analogy

FYI, a tap is the wrong tool for cleaning up buggered threads. It will typically allow a bolt to thread in, but the way it goes about cleaning be threads is to cut away metal. Hacking away anything in its path that isn't its mirror image shape. This compromises tbe strength of the threaded hole. Not something you want to do with a life safety feature.

The correct tool is a thread repair kit. These look like hardened bolts with a tapered end and grooves along the sides. You can even make your own from a hardened bolt with correct thread pitch. Grind a taper to help it get started, and grind some grooves along its flank.

The way these work is to kinda force the metal back into shape. Doesn't take metal away, just moves it around. End result is a much stronger threaded hole.

Like with a tap, the secrets are lube and going slow. Go in a little, then back out. Go a little farther next time, back out again. Then a little farther again (note, this combination is effective in other areas of life as well).

Patience is key. If you thought having buggered threads were holding up progress, imagine a broken tap or thread repair tool wedged into that hole. Keep that in mind to help keep you focused on going slow and careful.

JonC

colin00

I'll be sure to keep this in mind. Thank you!
(btw longtime lurker, literally all my research has stemmed from the forums, more than half of which were threads in which you've contributed to).

Which is why I'm a little worried and seeking third-party advice. Normally, like if I botched a single wheel stud, I'd have four more (wrong thought process, but you get my idea) to save me, but in this case, I can't afford to not have this bolt.

I've also read people timesert or whatever theyre called, but this was never an option for me. Maybe boring it out to support a larger diameter bolt hole, per Billman's advice, and replacing with a Class/Grade 12.9/10.9 or whatever the rating is.

Its funny you mention this, I was cleaning up some threads on another seat belt bolt I had, and tried driving that in to the cross-threaded/stripped hole late last night.
I felt like I accomplished a positive outcome, as I was able to thread in the replacement bolt further than before, but not sure if its just a placebo effect; I'd thread it until I hit the "stop", in/out/in/out like i would a tap, and made sure I didn't apply too much pressure. I'd also periodically make sure I ran that bolt through the die to make sure my threads were ok.

However, I'll be sure to look into that. I'm sure theyre made of HSS/carbide and would be better than random junkyard seatbelt bolt.


Appreciate the advice, guess this 55 gallon drum of KY can be used for more purposes than one, now!

Which is why I'm trying to make sure I get this one correctly the first time, and for the last. I'm usually pretty pertinent on threading the bolt in with fingers (not even a socket), but I was just so fed up with working on the car, I just blasted it in.



I'll update this thread with pictures and progress over the weekend.
Haven't been on a forum since 8thcivic.com from like 2014, and it's pretty rad to have a community of enthusiasts willing to provide feedback and advice to total strangers, so thank you y'all!