captured nut in the frame question

[concretejungle]

While re-mounting my ARB bull bar, i have found out that one of the bolts on the frame, or more likely the captured nut in the frame is damaged. I used a tap to chase each thread before replacing the bumper and the i also decided to purchase all new bolts.

Last night while tightening the bolts, the one bolt threads in, but it keeps popping loose. It's as if the captured nut has been opened up or reamed out for lack of better descriptive words.

I don't have the hardware in front of me, but i think it's a 10x1.25 bolt. My question is, should i purchase an 11x1.25 bolt and a tap, tap the captured nut to one size larger?

 

[jfz80]

good luck finding the M11..... its a tough one and everyone local will tell you it doesnt exist.

Toyota makes them for the driveshaft bolts but I believe it is a 1.0; ill see if i have extras but it may be difficult finding a tap that size.

arent the tops and bottoms the M12 bolts? if so id just go up one size tap and have at it.
Besides you have way more bolts in than you started with

 

[LandCruiserPhil]

Possible to be remove it and replaced. Recently did on the rear of a 100 series.

 

[jfz80]

He did that already on the other side

Ill let concrete confirm but this is a back bolt i believe, a little harder to get the welder to. If its m12 couldnt he step up to a 1/2'' tap which should be 12.5mm. Think that would be enough for threads to grab?

Was this bolt on top/bottom or side of bumper mount?

 

[pandathrust]

m10-1.25 are the bolts on the side of the frame in the front and the larger ones (top/bottom) are m12-1.25. I had a captured nut problem on the rear of my frame that was like a foot and a half from the frame opening when installing my 4x4labs rear bumper. I ended up cutting a hole in the frame and welding a new nut on the inside of the frame, and then rewelding a piece of 3/16" into the frame to close it up. That's not really necessary here though. If you decide to drill/tap, you are going to have to get rid of all the threads that are already on the captured nut by using a large enough drill bit and then tap, otherwise you run the risk of making weak and possibly cross threaded threads. If it is one of the side bolts and you can't weld a new bolt to the back, I'd just forget about it as there are already 5 bolts on that side, but if it is one of the larger top/bottom bolts I would break off the captured nut and weld on a new correct sized nut into that spot.

 

[LandCruiserPhil]

He did that already on the other side

Ill let concrete confirm but this is a back bolt i believe, a little harder to get the welder to. If its m12 couldnt he step up to a 1/2'' tap which should be 12.5mm. Think that would be enough for threads to grab?

Was this bolt on top/bottom or side of bumper mount?

If you can remove the existing nut I have also drilled small holes from the outside next to the nut, pulled the new nut into place, weld the small holes to secure the nut and grind smooth. There are more options to correct this. I hate foreign sizes and the use of SAE when designed for metric.

 

[jfz80]

m10-1.25 are the bolts on the side of the frame in the front and the larger ones (top/bottom) are m12-1.25. I had a captured nut problem on the rear of my frame that was like a foot and a half from the frame opening when installing my 4x4labs rear bumper. I ended up cutting a hole in the frame and welding a new nut on the inside of the frame, and then rewelding a piece of 3/16" into the frame to close it up. That's not really necessary here though. If you decide to drill/tap, you are going to have to get rid of all the threads that are already on the captured nut by using a large enough drill bit and then tap, otherwise you run the risk of making weak and possibly cross threaded threads. If it is one of the side bolts and you can't weld a new bolt to the back, I'd just forget about it as there are already 5 bolts on that side, but if it is one of the larger top/bottom bolts I would break off the captured nut and weld on a new correct sized nut into that spot.

agreed. That last line is the best fix, I just didnt want to help lift that thing again

and I saw your fix i bought crapped my pants for you. Good job on the repair though.

 

[LandCruisinMy93]

So if it's too hard to get to to weld, you center punch and drill 4 holes through the frame at the edges of the existing nut, punch the existing nut out, fish one into place with a magnet wand and thread a long bolt into it to put it in place and tack in the 4 holes you drilled and grind flat.

 

[concretejungle]

It is the rear bolt in the front frame rail. There are baffles in the frame there that prevent me from reaching this captured nut. My biggest concern is that if i was able to get the nut loose with a punch or other means, then i couldn't weld another one in place.

I am feeling that the easiest solution would be to drill this out to the next larger size and re-tap. That's my opinion anyways.

I would have to go back and look at the bags, but i "thought" the side bolts are M8 and the top and bottom bolts are M10.

 

[Whileemptyheadsdream]

It is the rear bolt in the front frame rail. There are baffles in the frame there that prevent me from reaching this captured nut. My biggest concern is that if i was able to get the nut loose with a punch or other means, then i couldn't weld another one in place.

I am feeling that the easiest solution would be to drill this out to the next larger size and re-tap. That's my opinion anyways.

I would have to go back and look at the bags, but i "thought" the side bolts are M8 and the top and bottom bolts are M10.

Thats correct and the next larger size that does not degrade the strength of the nut may be SAE.

 

[Rifleman]

Do you know a machinist, if so just have him make you a top hat style nut with the threads you need. If you don't know a machinist then i could make it for you and ship it to you, you would just need to pay the shipping, i would make you the nut for you for free. Once you get the top hat nut Then drill out the old riv nut in the frame a little larger to fit the O.D. of the top hat nut. Then install the new top hat nut in the frame and tig weld around the out side of the rim of top hat nut. If you want contact me and i can send you a drawing of what a top hat nut looks like. Once you see what i am talking about i think you will like it, the biggest thing is to tig weld it, not mig weld it in to place, that way you won't have a large weld bead to deal with and should end up with a nice flush fit. If you were here in Phoenix you could just bring your truck over to my machine shop and we could do all the work here, anyway Let me know if i can be of help.

 

[concretejungle]

i'm googling top hat nut...

the problem is welding inside the frame. I can't get a welding tip in there because of the baffles in the frame.

 

[Bluetribal]

A top hat nut has a rim on it like a small washer. So you would be welding that rim to the edge of the perfect size hole you drilled from the outside of the frame.

 

[concretejungle]

so you are saying the nut would be on the outside of the frame?

 

[akarilo]

So you might have to utilize one less bolt than the how many that are holding it on? I don't see a problem here. Just an opinion.

 

[retrofive]

So you might have to utilize one less bolt than the how many that are holding it on? I don't see a problem here. Just an opinion.

And you call yourself an 80 owner.

 

[Rifleman]

With a top hat nut, it has about a 1/32 thick rim on it that kind of looks like a washer, and the threads are inside the barrel part of the top hat. To understand what a top hat nut looks like Kind of think of our pass president, Abe Lincoln's top hat that he wore all the time. You drill the hole a little larger in your frame then stick the top part (that has the internal threads) of the top hat nut in to that hole. What your left with is just that 1/32 thick washer's rim fitting flat against the outside your frame. Then you run a bead of weld around that washer's rim on the outside of your frame. The reason i said to use the tig welder when welding that washer rim is tig only lay's down as much weld filler rod as as you want, so that way you can get a flusher fit. Now if all you have is a mig welder, you can use that too, but you will need to grind down some of the weld bead afterword to get a nice flush, flat fit.

 

[concretejungle]

I kind of wondered about that too, regarding the number of bolts. I mean, there are already 5 bolts on that one frame rail holding that side on and then 6 bolts on the other side....

 

[fj40ingkc]

Have any of you found the m12-1.25 or m10-1.25 here in the states @ToyotaMatt ? Hard to find rivet nuts or rivnuts here but i would imagine they are readily available in Japan or where jis hardware is sold . If any of you bought a box and have extra or know where to go I’d be happy to buy them -Max

 

[Potholesandwich]

Hey picking up on an old thread here...thanks for bearing with me. I'm trying to confirm size/thread on the captured nut in the frame behind the front bumper. Sounds like they're all the same for similar locations, but I'll provide location anyway: the captured nut on the TOP of one of the rectangular beams holding the bumper. The nut is in the rearmost of the holes on top of that beam, visible/reachable through the bumper vent holes.

It's bigger than M10. Sounds like an M12 x 1.25? Could one of you confirm? I have an M12x 1.75 and an M12x 1.5 and they won't thread in. And I can't see in there well enough to use my thread gauge without pulling the bumper. Thanks!