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Mikes Z car

How have you fixed twisted off rusty bolts?

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Hi all,

What have any of you done to repair rusty bolts that twist off? My twisted off fender bolt (passenger side):

post-18366-14150825587216_thumb.jpg

I had a lower fender bolt twist off on both sides of the car, the front bolt on both sides. Each side has two bolts at the bottom. After drilling out the old 8MM bolt on the driver's side I bought a helicoil but the tap that came with it broke off when tapping the new threads probably because I didn't know to back it out frequently to clear the shavings.

Broken off helicoil tap:_________Close up view:

post-18366-14150825589267_thumb.jpg

The easiest way to fix this I guess would be to ignore the twisted off bolt and put in a large #12 self drilling screw (AKA tech screw) with a washer right next to the twisted off bolt to hold the fender on if the sheet metal is solid. Or use (shudder) a moly bolt if the sheet metal isn't that strong. Has anyone else had to fix a twisted off bolt in an inaccessible area? How did you fix it? This is how I am fixing my twisted off bolt:

post-18366-14150825587856_thumb.jpg

After the nut is welded on the bolt will be removed and the tab bent back up flat with the body of the car where it was in the first place.

post-18366-14150825588505_thumb.jpg

Edited by Mikes Z car

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I broke a bolt extractor getting a broken exhaust stud out from under the thermostat housing on the head. A drill bit wouldn't even scratch it so I had to get a bolt welded onto it too then it backed out with the remnants of the old stud with it. A lot of trouble but that's the only way.

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Use penetrating oil hit it several times for the next day or two and see if yo can twist it out. next drill the tap out. I weld a new nut to the panel the replace the bolt. This way it all matches. I would not use a self tapping screw

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siteunseen,

I hadn't thought of welding a nut onto the extractor, thanks for the idea. I wound up cutting open the body and cutting off the nut from the back. The angle grinder cut off wheel went through the hardened extractor metal it just took a little while. After that to get off what was left of the nut I used the angle grinder with a grinding wheel on it. It made lots of neat sparks. Some of them got on me.

ajmcforester,

I only thought of the self tapping screw as a cheap easy solution but didn't like the trend away from originality so went with welding a new nut on. When I am done it will look original except for the zinc colored bolt.

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Try modifying an old flat blade screw driver or something that will grab the open slot areas between the tap cutting blades. It should back out with a little work and determination. I doubt you will be able to drill the tap as stated earlier.

If you wind up not using that hole, I would suggest a riv nut instead of a sheet metal screw

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I hadn't thought of modifying a screwdriver either. Well I get another chance on the passenger side, I got a new tap in the mail yesterday to do that side with.

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Dip the new tap in cutting oil or motor oil and don't force it. It will cut better if lubricated and they are very hard which tends to make them brittle. As you have found out they don't bend they break. If the other bolt breaks in the other rocker drill it out and even if the hole gets a little off center or a little too large as long as the tap has something to bite it will cut new threads. If the new threads are not full depth just don't over tighten the new bolt so as not to strip them. Also this is a good location for anti-seize... also I have found if you use too much force on these hidden nuts you can actually break them loose from the panel which is also a pain...

Charles

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Thanks Patcon,

Thanks for the info. Didn't know the nuts can break loose! What have you seen done to fix hidden nuts that break loose? The anti seize is a good idea. I might spray some anti corrosion on the inside sheet metal too though I don't want it too close to the work if I have to weld it.

Mike

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If I break a hidden nut loose the only good fix is like you did where you get access to the back and weld it back on...

Charles

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That is a good fix Mike. I can not think of a better way to do it. Also gives you the opprotunity to treat the inside.

Getting out a broken off tap is no easy job. A lot of force to break it off, so you need just as much or more to get it out.

Chas

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Think it might be a good precautionary idea to have a propane torch and penetrating fluid to soak and heat up the surrounding areas before attempting to unscrew?

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Someone should write a book on various repair techniques. I don't think I have seen a book like that anywhere.

I probably should have tried the propane heat on the passenger side bolt. Anyway I wound up drilling that bolt out like I did the driver's side bolt. I hope this weekend to carefully tap that passenger side hole to avoid breaking the tap by backing it out frequently. I have the helicoil for an 8MM bolt ready to put in the hole. I am a lousy welder but on the driver's side it seems I got the nut welded on to the sheet metal and the sheet metal pushed back into position and welded back flat with surrounding metal . That was fun! Doesn't take much to give me a feeling of accomplishment.

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Hi Mike, If you have one of those helicoil kits with 10 helicoils and 1 tap, be carefull with the tap. Its not made of top quality metal and can break with little effort.

Back it off every 1/4 or 1/8 turn and use plenty of lube.

I also use loctite on the helicoil as a precaution on holes that dont bottom out. Dont want the helicoil screwing through to the other side. I have had that happen. We used the original bolt from another car, but on grabbed the helicoil and screwed it through. Took a lot of work to get it out.

Chas

Edited by EuroDat

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Hey Mike, I'm not saying you did anything wrong, I would just like to repeat something my 70 yr old metalwork high school teacher back in 1973 told us. "When you tap or drill a hole you are the milling machine, but you are not as accurate so go slow with lots of lube, just like a woman." At 13 we laughed but didn't really know what he was talking about.

Proper proceduer was, turn the tap in 1/8th turn then back off 1/4 turn to allow the cuttings to fall and keep advancing and retreating slowly until you are all the way through, slow and precise. It occured to me that taps and dies are still sold but no one ever mentions how to use them.

Chris

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EuroDat and Grannyknot,

Thanks! I will print what you two said about going extremely slow with the tap and tape it to the tap kit I have. You two probably saved me from breaking another tap. I wondered if the coil might turn itself out with the bolt, I will be using locktite on it. Great idea.

Here is a picture of the weld on the sheet metal after the nut was welded on. I may redo what is visible here though I think the nut got welded on better since the bolt tightened down fine. I was laying on the sidewalk holding a flashlight to do this last part on the sheet metal. Mr. Lincoln Welder is probably turning over in his grave.

post-18366-14150825638371_thumb.jpg

(File name should read after welding drivers side nut)

Edited by Mikes Z car

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Think it might be a good precautionary idea to have a propane torch and penetrating fluid to soak and heat up the surrounding areas before attempting to unscrew?

Yes, heating up the old and using some wd40 or penetrating oil will most likely get it out. Forget cold. That's what I usually do to. But I would never use a helicoil. For my work I regularly need to drill out broken of 8.8 strenght bolts into cylinders all the time. What I do is grind it down to the surface, then use a pointer with hammer to center, then use a HSS drill, start small and go to the right size, then use a tap to make new thread.

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Here is a picture of the weld on the sheet metal after the nut was welded on. I may redo what is visible here though I think the nut got welded on better since the bolt tightened down fine. I was laying on the sidewalk holding a flashlight to do this last part on the sheet metal. Mr. Lincoln Welder is probably turning over in his grave.

[ATTACH=CONFIG]65991[/ATTACH]

(File name should read after welding drivers side nut)

Mike, I'm glad its not structural. Thats the problem when you are welding thin metal and its upside down making the degree of difficulty even worse. It doesnt need much to hold it together, but I think I would try to get welded.

I can welded ok;) but when its a PITA like this I get a friend who is an excellent welder to do it. Just have to put up with his remarks over my welding.

Something else to keep in mind if you use a helicoil.

The helicoil will probably be to long for the nut you are fixing. When you break off the tag (by turning the tool 90degrees and punching it through) it might push the helicoil through and stretch it out like a spring.

Check the length of the helicoil versus the tapped out nut and make sure the helicoil is a little shorter than the nut. If its not, then remove enough coils so it will be.

Chas

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EuroDat and Grannyknot,

Thanks! I will print what you two said about going extremely slow with the tap and tape it to the tap kit I have. You two probably saved me from breaking another tap. I wondered if the coil might turn itself out with the bolt, I will be using locktite on it. Great idea.

Here is a picture of the weld on the sheet metal after the nut was welded on. I may redo what is visible here though I think the nut got welded on better since the bolt tightened down fine. I was laying on the sidewalk holding a flashlight to do this last part on the sheet metal. Mr. Lincoln Welder is probably turning over in his grave.

[ATTACH=CONFIG]65991[/ATTACH]

(File name should read after welding drivers side nut)

Big welding tip, keep some scrap metal around and warmup by welding your scrap together, and getting the settings right. I can weld with the pros after 45 min to hour of warming up. Who knows maybe you can sell the scrap as art one day.

Helicoils can work well I have been able to not use any on my Z. I did use them on my old tuck do to the factory cross threading some things on the block and starter. Trick to using them that found was to use a punch and punch the material in opposite sides of the coil so it can't twist anymore then tap the coil to make sure their is no pinch points. Just be careful using the punch because the metal your smashing together normally has different hardness and your part can suffer more than the coil

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bartsscooterservice,

Nice idea to keep the original size thread. Grinding off the bolt would have worked for me on the driver's side bolt (didn't know about the grinding off idea). The passenger side bolt was shrouded by the fender and the fender didn't want to pull a few inches out of the way over the sticking out broken off bolt for some reason.

EuroDat,

I am also glad the repair is not structural! I know where I can get a proper welding job. I won't mind putting up with any comments about my welding, maybe they will look at it as a compliment on how they weld. That is a great idea on shortening the helicoil to the size of the nut. I had already put the helicoil in on the passenger side (welding worked on the driver's side) before I read your post. I put a couple of practice helcoils part way in to make sure they would go in okay before I put the loctite on and the tag broke off more easily than I would have thought just by turning. Both practice helicoils got stuck and didn't want to unscrew, maybe because the coil pushes out on the threads when unscrewing and/or because I didn't shorten the helicoil to the size of the nut. Both of their tags broke off, had to pull them out with pliers. Maybe some tags are easier to break off than others. The tap turned freely in the new threads before putting the practice helicoils in. Next I get to break the tag and put the bolt in.

ajmcforester,

Great idea on warming up to a welding task VIA a scrap of metal. I will put a piece of scrap metal with the welder and do that next time I weld.

I guess this is related, I was just told that for exhaust bolts an acetylene torch can be used on the bolt because the bolt will flow out of the hole leaving the threads intact in the block metal.

Edited by Mikes Z car

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Mikes Z car:

What kind of welder were you using? MIG? Shielding gas or flux core? What amperage welder?

Charles

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Patcon,

It is a Lincoln "handy mig" with two switches which give four amperages. The box says it is good for between 35 and 88 amps. I have a pure argon tank I use for the shielding gas and I can hear the gas coming out of the end of the "wand" when I pull the trigger to weld. The wire is set to a slow speed, about a "2" on the speed dial that goes up to "10". I use the next to the highest amp setting, I have never used the maximum amperage setting as I have been afraid of blowing holes in the sheet metal. I may be being overly cautious. Didn't want to put a hole in the z car.

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I had a century 100 amp welder at one time and it welded like a "drunk monkey". I bought myself a Hobart 230 last year for Christmas. Much easier to weld with a good welder especially if it can be run at 100% duty cycle. I have lots of ideas for your welds but it is much easier to figure out by feel. Sometimes I get little beads like that when my heat isn't high enough, metal is too dirty or not enough shielding gas. I usually run at the highest setting I can with out burning holes. You can also avoid holes by triggering in short burst and not holding the torch square to the surface. If the metal gets red hot the shield gas can blow holes in it. I have found on my Z I use the #1 and #2 settings on my welder out of 12 settings. The metal is very thin and it is easy to blow holes in it especially if it is on a panel that got stretched a lot when it was stamped.

My speed setting is about 22-28 on those first 2 settings which I think is inches per minute (?). I like it to sound like frying bacon real consistent sizzle and very little popping. Generally when I am getting popping it is because the metal is dirty or rusty. A little die grinder with a 2" 36 grit rowlock pad works good for this and quick. Praticing on a test panel to find some initial settings is a good idea preferably a Z panel because the alloy and the gauge will be similar. My 2 cents...

Charles

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I have a pure argon tank I use for the shielding gas

You're using the wrong shielding gas. For general purpose MIG on carbon steel, you should run 75% CO2 / 25% argon mix. If you use 100% argon with the MIG, you get proud beads and very narrow fingerlike penetration. You'll be tempted to turn the power up to get the bead to spread, but that's not the solution. The solution is to use the correct shielding gas.

I went through this myself about a year ago because I was trying to minimize the number of bottles I had to maintain. I figured that I could share the same 100% argon bottle between the MIG and the TIG, and I was mistaken. It doesn't work right.

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Patcon,

Thanks for typing those tips in, I watched some videos on welding but they didn't mention techniques that you did. I don't know if a better welder is an option for me (for one, don't have a ready access to 230V) but for the work I need to do a crappy one might be okay especially if I can improve technique. I'll clean the rust off of the metal next time. I mostly get popping, not sizzling so I know the arc isn't sustaining well.

Captain Obvious,

I will get a bottle of the CO2/argon mix, thanks for pointing out the effect of the gas.

Just when I thought I didn't know anything about welding it turns out I was right. :)

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