Removing a stuck, hardened-steel, bolt....

[AJMD429]

I knew something wasn't right when I looked back while mowing to see if the stiff-stalked weeds were getting cut or just bouncing up, and I saw my grader-blade sitting there in the middle of the 'pasture' I was mowing. The bolt that basically holds it on had sheared off. I had used it and the front end loader to flip up a microwave-oven-sized rock that was protruding up enough to hit the deck-mower blade, but it wasn't a heavy job, and everything worked fine, but 100 yards of mowing later, there sat the blade.

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So what I don't know (and maybe I'll have to get hold of the John Deere dealer during their open hours) is whether the nut that is welded onto the blade, that this bolt goes to, is just welded there, or if there is some kind of pinning or welding that held the bolt into the nut versus just friction. It never appeared loose, and I never had to tighten it, so it makes me wonder. If so, I may have a mess on my hands.

Otherwise, if the bolt-tip isn't epoxied, pinned, or welded to the nut, I should be able to get it out and replace the bolt.

It is hardened steel, so I'll need a way better bit than I own to drill it if I try to use a broken-bolt-extractor, but I can either buy a really good bit and see if hammering an extractor into it will give me enough torque to back it out, OR I suppose I could weld something to it like another hardened bolt, and if my welding skills are good enough, use THAT as my extraction 'handle'. My fear there is that if I got the bolt threads molten by being too sloppy with my welding that I could really make things worse (and I'm not a very experienced welder but do have a MIG unit, and a friend who has been a welder for his living for many years who could help).

So....

a) does anyone happen to know if the bolt-tip is likely fastened with anything other than friction and the usual rust that penetrating-oil can loosen....?

b) do you think I'd be better off drilling for an extractor, or welding something to the bolt, or perhaps a THIRD way I haven't thought of....?

[Trailboss]

So....

a) does anyone happen to know if the bolt-tip is likely fastened with anything other than friction and the usual rust that penetrating-oil can loosen....?

b) do you think I'd be better off drilling for an extractor, or welding something to the bolt, or perhaps a THIRD way I haven't thought of....?

The fine threads on the bolt would suggest that friction and now rust is now holding the broken piece in the nut.

The hardened bolt is probably case hardened and so the center is softer and can be drilled for an extractor. Just use a carbide drill bit. Also use heat and penetrating oil before backing it out.

[.45colt]

I don't know what You have on hand for applying heat Doc, but I can say that a few years ago I bought a map gas set from Home depot .(yellow) bottle) it will get some pretty big pieces of steel glowing red/orange in no time and I find it invaluable around the shop when things are stuck. I bet that bolt would spin out of there in short order.

[GunnyMack]

Doc start by soaking it with a penetrating oil ( kroil is the best) , let it work a day or 2 with continued applications of oil. Then heat it up. A couple times like that ya might spin it out by hand.

I would drill it out , small bit 1st, go up through the sizes until it's hollow then try an extractor. Or a flat punch and tap it out with a hammer.

After you get it removed use anti seize on the threads and ya won't have to fight it again.

[marlinman93]

With the broken bolt sitting below the surface there's no way to weld to it and not end up welding to the adjacent material. Then it's in there permanently!
First thing I'd do is heat it up a little, and then put penetrant on it as the heat will suck it into the threads. Repeat this a few times before you ever start drilling.
Then get yourself a left hand drill bit as close to the thread size as possible. Pre drill the hole with a right hand bit, unless you have a set of left hand bits as I do. Then when you get it drilled with the smaller bit, switch to the larger left hand bit. In most cases the left hand bit will at some point grab the broken bolt and simply unscrew it as I drill. Works in 90% of the broken bolts I've done, and I rarely use my easy outs.
An easy out or extractor works by tapping it into a drilled hole. So the harder you pound it in, the more pressure it puts against the threads, which only makes broken bolts tougher to get out. The left hand drill bit simply grabs it and unscrews it if penetrant is applied first.

[Alan in Vermont]

How many marks on the head of the bolt? Grd. 2 will have three, Grd. 8 will have six. My bet would be a Grd. 8, drillable with a good HS drill.

Several ways to approach this. Is the nut easily accessible, enough so that a right angle grinder can get at the nut? If so grind the nut off and weld on a new one.

Assuming not, then I would try a left handed drill bit. Yes Virginia, there really IS such a thing, even if the people at the common hardware store (think Ace, Tru-Value, etc.) clerk will probably look at you like you have two heads when you ask about one. McMaster-Carr will have them and they ship fast. A an industrial tool supply may have them. Turn the blade upside down and use a GOOD penetrating fluid to fill up the area on top of the broken stub. Kroil (Kano Labs) or "Knock-R-Loose(CRC Chemicals) are good ones, even better is a 50/50 mix of transmission fluid and acetone. keep it wet and let it soak as long as your patience holds out. Drill a small hole (3/16" would be good) as close to the center of the broken off end of the bolt as you can. Then swap for your left hand bit, one as big as will get into the bolt without getting into the threads. Put some weight (as in "lay on that sucker") on it and use low speed. If your karma is good the bit will bite into the bolt and unscrew it out of the nut.

Don't even think of using those spiral Easy-Out things. Their reason for being is to fill a drilled hole with metal to hard to drill out.

Hope all this rambling helps you out.

[hayabusa]

What mm3 and A said is the way I have used for years. It works.

Busa

[piller]

I used an easy out once. What a mess. It broke off and I had to take it to a shop with a pro who got it out, but wouldn't let me see how he did it. I think he made a good living by fixing things that amatuers like me messed up with easy outs.

Heat and cold both make the metal move. Expansion and contraction can break the rust out of there.

[fordwannabe]

I do a fair bit of mechanic work around here and I agree with Alan in Vermont 50/50 mix of atf and acetone beats anything I have ever used for loosening rusted bolts and I WAS a big krill fan. I just want to ask is the bolt broken in the threaded part of so you may be able to use that MIG and weld a nut on the stub and then ratchet the rest of the stub all the way through.