Sheared bolt repair

[aasukisuki]

(I've posted this in Off Topic because it applies to my wife's VW)

Maybe you guys can help me out with this. My wife has a VW Cabriolet that we're fixing up for her to put around in during the nice months. When we purchased the car it had a rusted gas tank. I replaced the old, leaking tank with a new one, but in the process of dropping the rear axle (crossmember) I sheared off one of the bolts that connects the axle to the chassis. I've started to drill the bolt out, which is fine, but the bolt is welded in from the top of the chassis. So once I get the bolt drilled out, how do I go about removing the rest of the head that's welded in? Here are a couple of photos:

The bolt on the right is sheared off:

This is taken from the top. You're looking through an access hole that's located under the back seat. The scratched up circle is the bolt head:

 

[Nance]

Can you drill it on out and retap it ?

 

[72fastback]

try grinding the weld with a die grinder if you can't get to it with an angle grinder.then if you can drill a smaller hole in the bolt. Tap it to a smaller diameter bolt.Then if the remaining weld is weak enough you might be able to break it .{if you can heat it up all the better} Of course this is if the bolt is in a threaded hole and you want to keep the threads.If not grind and hit with a center punch till the rest of the weld breaks off.If it is only welded on top with not to much penetration this should do the trick.

hope this helps.

 

[aasukisuki]

try grinding the weld with a die grinder if you can't get to it with an angle grinder.then if you can drill a smaller hole in the bolt. Tap it to a smaller diameter bolt.Then if the remaining weld is weak enough you might be able to break it .{if you can heat it up all the better} Of course this is if the bolt is in a threaded hole and you want to keep the threads.If not grind and hit with a center punch till the rest of the weld breaks off.If it is only welded on top with not to much penetration this should do the trick.

hope this helps.

From what I can tell, the hole is not threaded. The bolt and it's large head (it's like a round head attached to a washer is the best way to describe it) is just welded in place. Unfortunately the access hole isn't big enough to get a grinder into. It's not even big enough for me to get a rotary tool into (I can get the actual cutting disc in there, but the rotary tool itself is too big to fit into the opening). If I heated the bolt head with a torch from the top and then hit it with a center punch from the bottom on what remains of the bolt, do you think that would break it free, or am I better off just trying to drill it out?

 

[machman_73]

I can't really tell what you,ve got. Is that a allen wrench type bolt head. Are you positive it's welded? Thought it might just be rusted real bad.

 

[72fastback]

unless you are really confident with a torch and cut it out I guess drilling is the only thing left.just make sure if you cut it out with the torch to cover anything that can burn underneath with a piece of leather,fire resistant blanket or a soaking wet rag.

 

[machman_73]

Heat it and beat it.

 

[72HCODE]

i will suggest using a dremel with a carbide cutter, and a set of hardened drills with a Titanium Nitride coating.

first flatten out the head of the bolt if your off center. center punch the bolt, then drillout the center right through with the coated drills.

use the carbine cutter and slowly cut out the center of the bolt just before the threads.

then use the correct tap and and retap the bolt hole, if you work slow you should be able to get it back to normal.

 

[aasukisuki]

Great Success!

I ended up using a 1/2" drill bit and some motor oil (I couldn't find any cutting oil at any of the stores I stopped at) and finished drilling the bolt out from the top. I set a 10mm bolt in the new 1/2" hole and secured it with some JB Weld (since I don't have a welder )

Thanks for the advice guys.

 

[machman_73]

Good job aa. I know drilling out bolts is a pain in the butt.