Cross threaded seat bolt/captive nut PAIN

Russ

Russ

Club Member
Hi all,

About a month ago early one morning late for work I cross threaded one of the front seat bolts.

Even worse is that the captive nut behind fell off as well.



Two problems:

I cannot for the life of me source a bolt or nut or tap/die to match the size of Nissans fine thread and odd sized seat mounting bolt. I've tried all sorts, any ideas please? Failing that I'll have to change the bolt and have an odd one :(

Has anyone got a clever idea on fixing my captive bolt? I have a few ideas.

One, cut back of the seat mounting frame to allow access, re-weld in new nut, weld back in my access hatch.

Weld a nut to the back of a plate, and then weld this to the face of the sub frame.



Please never make the same mistake as me :)
 
Bantambunny

Bantambunny

Well-Known Forum User
Mate my front seat teeter-totters like a childs play toy!

Cross threaded both nuts/bolts and ruined the whole thing. I've been trying to figure out a way to bolt it in securely for when i sell it but short of taking it to an engineers shop and getting them to helicoil it i can't think of any answer apart from grinding out the old nut and welding a nut on the back under the car or maybe tapping the old nut and buying oversized bolts?
 
Russ

Russ

Club Member
Ok good, we can solve this together.

The real problem is that the bolt size is so odd to this country it seems. Snap on, any engineers I've rang, fixing & fastener shops cannot get me a tool that taps the same size. I haven't given up on this yet. I'm guessing you won't be able to get the right sized helicoil if it's an odd size.

Another option is to get an engineer to turn me a new nut on his lathe, again sounds like a lot of work.

I found the bolts, 25mm long min order 200, 30mm long min order 100. I don't know what they look like so could be shiny silver, however it was about £25 for the bolts, so say £40-£50 I'll be the proud owner of 100 sets of front seat bolts/nuts.

My concern would be the front nut/bolt takes a load in a forward direction in a head on crash, which is why the nut is mounted inside the seat subframe. I counted about 25 spot welds to remove the frame as one, I figured going in from the top or behind would be better, cut a hatch with a disc cutter and a thin cutting disc.

So long as it ends up safe, and looks right I don't mind :) I don't want a silver bolt, I don't want one with a different shape head really, much as no one will notice I'll know it's wrong and that my funny five minutes cocked it up :)
 
JakTheRuby

JakTheRuby

Club Member
Is it not possible to just take the seat out completely, then grind off the old bolt and drill a slightly bigger hole and push through a new screw, put a small weld on the bottom to anchor it and then get a nylock nut with some of that weld paste on and put the whole shebang back together? I have no idea what the layout is (obviously) but it seems such a trivial problem. I'll get me coat...
 
Bantambunny

Bantambunny

Well-Known Forum User
lol, the bolts are mounted under the carpet behind the floor rather than on top.

They go through to fresh air so they must come out under the car somewhere. Without putting mine on a ramp i wouldn't be able to get to them.

My thoughts are get some thick bolts, slightly thicker than the ones on there already, get a grinding attachment the same thickness and then grind through, stick a bolt behind, spot weld to hold it in place then bolt through the floor into the bolt, safe and sound
 
JakTheRuby

JakTheRuby

Club Member
Bantambunny said:
...My thoughts are get some thick bolts, slightly thicker than the ones on there already, get a grinding attachment the same thickness and then grind through, stick a bolt behind, spot weld to hold it in place then bolt through the floor into the bolt, safe and sound
Click to expand...

That's exactly what I meant. I think if you read it again you'll see. If it goes right through to fresh air (what I was predicting having never seen one in the metal), then it's a reasonably simply fix (albeit an involved and long winded but not difficult if you know what I mean). Phew!
 
P

pmac

Well-Known Forum User
Just use a seat belt mounting plate like we did on Nicks car when we put the Ser 2 belts in the ser 1 car. Job done.
 
Russ

Russ

Club Member
Pmac: Ahh that's a good idea, I'm presuming this is an aftermarket seat belt mounting plate, not a Z32 part as such? Are seat belts a common bolt size? My car is pretty original and nice so wanted to avoid having an odd looking shiny bolt on the seat mount. Thanks :thumbs:

Bantam: I have my carpet out atm to solve this, have attached a picture so you have a better idea. Is it the front or rear mounts that are you problem? The front bolts go into a pressed steel rail that is three sided and has only a small hole behind it so no access, hence my plan to cut into it (nooooo) or weld a plate to the front.
 

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Russ

Russ

Club Member
Which of your bolts are bad mate, I'll go get you some close ups of under the carpet so you know what you're dealing with.
 
Russ

Russ

Club Member
My local rally supplier guy will have those in a big tub under his workbench I think, seem ideal. If I use a hole cutter to enlarge the hole the nut can sit inside on the back of that plate, and I'll have only raised the front by the thickness of the plate. Hopefully this won't be noticeable to the way the seat slides once the carpet is in the way :)
 
Bantambunny

Bantambunny

Well-Known Forum User
If you put the plate in front of the current metal the seat won't bolt into the place, its a very tight fit. What i would do is mark around the plate, grind/cut out the equivalent area, cut along the top bar about 2mm in so it sits flush then clamp and weld the plate in line with the old bolt hole, weld along the floor pan and angle grind the top to the required height then weld along the top, grind it all off, refit the carpet and hey presto, perfect fit seat. Just a pity i don't actually own a mig welder.

I can see a bit of money coming mr mac's way very shortly :D

Russ said:
Which of your bolts are bad mate, I'll go get you some close ups of under the carpet so you know what you're dealing with.
Click to expand...

Both of the drivers side, it's like driving a rocking horse at the moment unfortunately lol
 
P

pmac

Well-Known Forum User
Bantambunny said:
If you put the plate in front of the current metal the seat won't bolt into the place, its a very tight fit. What i would do is mark around the plate, grind/cut out the equivalent area, cut along the top bar about 2mm in so it sits flush then clamp and weld the plate in line with the old bolt hole, weld along the floor pan and angle grind the top to the required height then weld along the top, grind it all off, refit the carpet and hey presto, perfect fit seat. Just a pity i don't actually own a mig welder.

I can see a bit of money coming mr mac's way very shortly :D



Both of the drivers side, it's like driving a rocking horse at the moment unfortunately lol
Click to expand...
Bring it round then;)
 
Russ

Russ

Club Member
So the front bolts, not the rear nuts. I'll get my camera out, sounds like a good plan :) I'll just pretend in my head it's a mounting upgrade for my passengers safety...
 
D

Dunk300zxTT

Well-Known Forum User
Russ, did you solve this? I have a load of Metric fine thread taps at work that I could make something with if you still need it?
 
Russ

Russ

Club Member
LOL yes all sorted thank you. I forgot to post my solution!

Guy at my car restorers had a set of these really industrial looking riv nut kinda things and matching bolts :) We drilled out the spot welds to release the old nuts then fitted them. They have a really large area to the rear surface, I think the seat mount would deform and pull off before the nuts came through, and if that was the case I think both me and the passenger would be a stain from the impact to do that. From outward appearances (apart from having the wrong shape bolt head, still black though) you'd never know the difference :)

Will get pics of my camera at some point to show them fitted. I'm still kicking myself about it though, but the pain has taught me a pretty permanent lesson :)
 
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