Removing broken bolts

[enjenjo]

Here are some tips on getting broken bolts, or bolts with the heads stripped, out.

First thing to remember, don't get too aggressive at the beginning, start with the least destructive methods first. Then you have to analyze the problem. decide if the bolt is stuck from rust and corrosion, or from other causes, deformed or bent threads, galled from heat or material properties, or the fact that the head is stripped. If the head is just slightly stripped, it's sometimes possible to get it out with a 6 point socket, or if the head has rusted to a smaller size, a metric socket will sometimes remove it. ViceGrip make some special pliers just for removing bolts with stripped heads. They are well worth the price.

If the fastener is accessible from both sides, and the nut isn't permanently fastened to the part, cutting the head off with a die grinder, or splitting the nut may be the best way to get it out. If the nut is caged, or welded to the part, you can weld a larger nut to the head of the bolt, and use that to remove the fastener. When doing this, let the fastener cool before trying to remove it.

If you have to heat a fastener to get it out, don't heat the part, heat the fastener. And let it cool to some extent before trying to remove it. You can also use heat and cooling together, heat it, and touch the bolt with an ice cube, repeating several times. You can also use penetrant or paraffin along with the heat. What you are trying to do is break the rust bond between the parts. Once you can get the bolt to move, stop and regroup. turn it one way, and then the other, adding penetrant, then work it back and forth some more. patience will be rewarded.

If the bolt is broken off, and it's sticking above the part, you can weld a nut to it, using plenty of the heat on the fastener. then, let it cool completely before trying to turn it. Put a wrench on it, and tap it back and forth to break it loose. Add penetrant, and work it out.

If it's below the surface of the part, many times you can still weld a nut, or a piece of strap to it with minimal damage to the part. Finish removing it like the case above.

If you have to drill a fastener, drill a pilot hole first, clear through the bolt if possible. squirt penetrant into the pilot hole, and let it set before continuing. Then continue drilling with a left hand bit. Or, you can use some of the new bolt extractors with a left hand drill bit built into the end. Very often the bolt will come right out.

Welding a nut to it can also be useful for removing a broken screw extractor. if that's not possible some of the other methods offered are excellent. The last resort is EDM machining, which can be expensive.

There are some special cases, one of which is countersunk screws, with stripped heads. My favorite method involves drilling the head off, separating the parts, and removing the stub with one of the other methods.

Another special case is exhaust manifold studs. Since the parts have been heated regularly, heat is not near as effective as it is in other cases. Also many times the threads have galled making it more difficult. In this case, I heat the casting to bright red, cool the fastener, and lots of patience. Once you can get it to move, penetrant, and more patience.

Steel fasteners in aluminum castings, or die cast zinc, are another special case. Most times the casting corrodes into a white powder, that very effectively locks the fastener into place. I have found PB blaster works good the dissolve this corrosion. It is of course better to free the bolt up before you break it, so I will drill a small hole in the fastener, to allow the penetrant to get to the end of the bolt. In many cases this will allow the fastener to be removed with your hand after breaking it loose with a wrench.

[flt-blk]

My favorite has always been PB blaster and heat.

Using a torch, heat the part and as it cools give it a shot of PB, it will wick
into the threads.  Do this at least twice before putting a wrench on it.

I recently used heat and wax, worked as good as the PB and took fewer
cycles.

I ruined a VW head once in my GTI due to lack of patience, broke off 2
EZ outs.  I ended up removing the head and had to have a machine shop
take it out and fix it with a helicoil.

[unklian]

Where I used to work,the over paid Dumb A** Maintainence Mechanic used to bring stuff around for me to remove broken bolts.

These were usually small Allen bolts that had been over tightened,and broke off just below the surface.
Usually you could back them out with a light touch and a small center punch or scriber.
OR just press your thumb over the top of the hole,and give it a twist,
to back it out.
Less than 1 in 10 needed to be drilled.

I used to give him a hard time about getting me to do his work for him,
since he made sure I knew how much he was getting paid.
So one day he comes around with one of the big Bosses(like I'm supposed to be intimidated)and this piece with a broken bolt in it.
As I'm telling him that this is his job,and I shouldn't have to do his work for him,I back the screw out with my thumb and hand it to him.

They both left,and he never brought another broken bolt back again.

[unklian]

I only use name brand EZ Outs,
and drill the hole slightly larger than the instructions call for.

[DocsMachine]

Broken-off Easy-Outs aren't that much of a problem. There's two solutions:

A) Get a solid carbide or solid cobalt drill bit. They can be ordered from any machinist supplier like MSC, Traver's, J&L, ENCO, McMaster-Carr, etc. Get a "stub length" or centering drill. You'll need a rigid setup, like a vertical mill preferably, but a big drill press and having the part bolted down or clamped firmly works just as well.

A short carbide drill can cut through a broken tap or easy-out like butter. However, they're brittle- personally, I expect to lose the drill every time I have to pop a tap or EO out.

Or B) Make a tiny holesaw. Really.

Set the part up in a drill press so the hole is centered and vertical. Get some thinwall brass tubing (try a hobby shop) a bit smaller than the thread diameter of the broken part and chuck a short section in the drill press. Mix some Clover valve grinding compound with a thinning agent- if it's oil-based, use a light machine oil (not WD-40) if it's water-based, use water.

Use some clay, cardboard, Play-Doh, silicone or whatever you can find to make a "dam" around the broken part, and fill it with the abrasive slurry. You don't need to make it deep or wide, just enough to keep the tubing section wet.

Set the drill press to it's slowest speed, and lower the brass tube onto the broken off part (centered well, naturally.) Expect the tube to wear and maybe bind a bit, depending on the shape of the end of the broken part.

Eventually it will wear itself a kerf. Now hang a weight on the handle of the press to keep pressure on the tool, and go have a cup of coffee. Periodically refresh the abrasive.

In anywhere from five minutes to two hours, the tube will have sawed through the broken part, allowing you to pick the 'core' out, and then pry the bits out of the thread.

Doc.

[Jokester]

Another option is to drill it out using a reversible drill and a left handed drill bit.  Usually once the bit bites it will screw the broken piece right out.  

I have also sawed a groove in the top of a stud and used a large screwdriver to get it out.

Of course neither of these will work if they are vigorously rusted in.


.bjb

[unklian]

If the hole is tapped through,sometimes a regular drill bit will grab enough to push it through.


Of course,the expensive answer is Sink EDM.
But if the part is valuable enough,it can be worth while.

[enjenjo]

I added more to my original post, I ran out of time this afternoon.

You should also hear my theory of Progressive destruction. Sometimes you just can't get things apart without destroying something. In that case, destroy the cheapest part first. If that doesn't work, proceed to the next most expensive part, until you have destroyed them all. At that point you can throw it away with a clear conscience, secure in the thought that it is of no further use to anyone.

I appreciate the other posts on this thread, and welcome any others. We can all learn from each other.

[rooster]

On my skid loader their are 40 studs per side , removing the nuts broke the studs , about 8 per side, most had enough stud sticking out to use Craftman broken bolt extractor

[Bruce Dorsi]

I have encountered almost all of the situations, and employed all of the techniques mentioned previously.  

Rarely, do I have the luxury of being able to set-up the piece in a mill or drill-press, so I have to resort to hand-held drills.

Although they are sometimes useful, I am not a big fan of tapered Easy-Outs.  ...If the remaining wall thickness after drilling is thin, the tapered shape of the Easy-Out wedges the fastener walls outward, making the fastener even more stubborn to remove.  

Since most tapered removers only bite at the top of the drilled hole, sometimes driving a piece of square keystock into the hole provides a more effective grip.

Broken taps can often be removed by using a hammer and straight punch, if a tap remover is not available.  ....The brittleness of taps will usually cause them to break apart when struck by the flat-ended punch.   .....This technique is usually reserved for taps broken in hard materials.  Unhappy results can occur if the material is aluminum or cast-iron.

Unfortunately, sometimes fasteners break where torches or welders are not available.  ......I have tried unsucessfully to remove a 5/8" Grade 8 bolt which has broken below the surface of a cast-iron casting.  .....I was unable to unscrew it with a center-punch, and it laughed at my HSS and cobalt bits.  ....The only carbide-tipped bits I have are masonry bits,  but they had no effect.  .....I also tried a plumbers' air-acetylene torch, but that was ineffective.
....I'm sure that welding would be effective, but that would mean hiring a portable rig to go out to the equipment.   .....Any other suggestions?

[enjenjo]

One time I had to fix a TD21 dozer that had broken down 1/2 mile from the nearest road. All the bolts holding the drive sprocket to the hub had broken off on one side, 16 5/8" L9 grade bolts. No power available, and the only power tool I had was a cutting torch. So I burned a hole about 3/8" in the center of each bolt, and removed them with easyout extractors, through the bolt holes in the drive sprocket. I worked all night, but had it done for the next work shift in the morning.

[Bruce Dorsi]

1/2 mile from the nearest road...No power available... I worked all night...

Moonlight, or torchlight?

Those are the kind of jobs you never forget!

Sometimes, it's easier to let the NEXT owner worry about it!

[DocsMachine]

nfortunately, sometimes fasteners break where torches or welders are not available. ......I have tried unsucessfully to remove a 5/8" Grade 8 bolt which has broken below the surface of a cast-iron casting. .....I was unable to unscrew it with a center-punch, and it laughed at my HSS and cobalt bits. ....The only carbide-tipped bits I have are masonry bits, but they had no effect. .....I also tried a plumbers' air-acetylene torch, but that was ineffective.

-Grade 8 isn't all that tough. HSS is harder, but not by much. I suspect your "cobalt" bit was only coated.

The masonry bit has the wrong tooth geometry for the job- it's really meant more to "crush" rock than shave steel.  Pick up a real, live, micrograin carbide stub-length carbide drill bit, and you'll be surprised how easily it slices through that bolt. As I said earlier, they're brittle though, buy a couple.

I watched a guy drill out some broken bolts, several of which that had easy-outs broken off in 'em. He used a stubby solid-cobalt spade-point drill and a lot of pressure on the drill press arm. The bit actually heated the chip to red hot and peeled it away in it's soft state. He said he could drill through a file or the shank of an endmill with that technique.

I doubt you can apply that much pressure- at least as easily- in a handheld situation, but again, the G8 bolt isn't that hard, and a proper carbide drill should take care of it.

If it were me, I'd centerpunch the bolt stub so i can be sure the drill starts pretty well centered. Then I'd drill it first with a 1/8" or 3/16" carbide, then move up to a carbide just a frog hair smaller than the root diameter of the bolt (probably 1/2" or so.)

Once it's drilled, and if you're lucky you'll have been just off to one side enough that the thread root is exposed, a little work with a scratch awl or punch should be able to pry what's left of the threads out.

Doc.

[Bruce Dorsi]

-Grade 8 isn't all that tough. HSS is harder, but not by much. I suspect your "cobalt" bit was only coated.

If it were me, I'd centerpunch the bolt stub so i can be sure the drill starts pretty well centered.

===========

Thanks for the advice, Doc!

I'm guessing that it is a grade 8 fastener, but it may be something tougher/harder.  .....My centerpunch wouldn't mark it!

I believe my cobalt drills are not the coated variety.

I knew the carbide-tipped masonry bits are crude and of the wrong geometry, but I wanted to see if they would have any effect.  
....I will try the suggested carbide bit on my next go at it.  ...Fortunately, it is not a critical piece for the use of the equipment.

[DocsMachine]

I'm guessing that it is a grade 8 fastener, but it may be something tougher/harder. .....My centerpunch wouldn't mark it!

-Unless you have some exotic aerospace fasteners, or it's something oddball like an ARP race engine rod bolt, I doubt it's harder then Grade 8. And even on those sorts of cases, it's not so much that the bolt is "harder" (which really just makes it brittle) it's "tougher", as in more resistant to elongation and cracking.

More likely your centerpunch was a wimp.

Most pin punches and centerpunches I've dealt with were mediocre to decent steel- hard enough to mark mild steel, cast iron and aluminum, but too soft for anything harder.

A good centerpunch will be hardened, then draw-tempered like a chisel, so the point is around Rockwell 50-55C (about as hard as a file) while the rest is R40 to 45C. This makes the point hard enough to mark and not deform, and the body soft enough to not shatter when struck.

Doc.