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While attempting to replace the brakepads, the lower bolt that that pins the caliper shield sheared off. What is the preferred method to remove the bolt shaft without damaging bolt receptical? It's not really a nut, though from the bolt's point of view it is no different than a nut.

Solutions that avoid removal of the rotor housing assembly from the vehicle are preferred / highly valued.

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UPDATE: The good screw is a M6, I suspect both are identical

Photo of sheared off bolt: it is almost flush with the receiving body:

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  • if you can grind a slit in it with a grinder or dremel, you might be able to use a flathead to remove it. – dandavis May 15 at 19:50
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The standard way to remove sheared bolt would be to drill a hole in the center of the bolt at use an "easyout" bolt extractor to unscrew the bolt.

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If there is enough of the bolt sticking out, you might be able to grab it with a pair of vise grips and twist it out. You might also cut a slit in the edge and use a slotted screwdriver to twist it out.

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That "nut like" property is called a tapped hole. Either into a casting, through a thick stamped steel piece, or sometimes they actually weld "nuts" to the backside of a piece of stamped steel.

Sometimes the holes are "blind" meaning they just end in solid metal. Usually on a piece like this it will be a "thru" hole. That's good news because it becomes easier to access the backside to saturate it with penetrating oil.

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This is a tap. This, run through a hole, will cut threads into the hole. The top one is a "bottoming" tap made for finishing up a blind hole to cut the threads as low as possible. The other two are for differing hardnesses of material.

Penetrating oil quality varies dramatically. The worst is WD-40 - it's a Water Displacer (#40), not a penetrating oil. Something homebrew or Liquid Wrench would be better. The best is, by all reports, Kroil.


What happened was simple: the threads gripped the bolt shaft so hard that the threads held on better than the shear strength of the bolt shaft. Unfortunately, an "Easy-Out" or similar will have exactly the same problem -- it will still need to "break loose" that very stiff binding to the threads, except it will have even less material diameter to work with. The only way an E-Z-Out will work is if you can loosen the bolt remains first by a combination of penetrating oil, hammering, or heating.

And yeah, if you could have done those things before unscrewing the bolt initially, it wouldn't have snapped off. Probably. It does help to direct your torque "square-on" rather than at a tilt, as you'll get using a socket wrench particularly with an extension. That's why taps have T-shaped handles, so you are twisting square-on to the hole.

Eventually you will get a "feel" for when you're just torquing too hard on a given size of bolt, and will stop there and hit it with Kroil, heat and more Kroil before you snap it off.


What I do in cases like this is remove everything I can off the metal part, and just get another one at the junkyard. OR... I hire a machine shop to remove the former bolt, or I do it myself with this procedure:

  • Use a punch to put a little dimple dead center on the sheared bolt.

  • Drill that out to 1/8", then drill it slightly larger with every drill I have.

  • You can pause here and see if an "E-Z-Out" will be profitable, but I would not expect this, and don't go all gorilla on the E-Z-Out and break it off in the hole!! If you did, see "buy at junkyard".

  • Keep drilling 1 size larger.

  • When you near the size of the threads, you'll start to see the threads fall out of the hole in broken off crescents. You're almost home.

  • At this point, try using a tap of the same size and thread pitch of the hole. I am guessing this hole is 6mm but you'll need to measure the pitch off the other good screw, by seeing which metric nut goes down it effortlessly. Unfortnately the metric boys did not set any standards for thread pitch, unlike the NF and NC standards.

  • If you are lucky, the tap will "seek toward" the original threading, carving out what remains of the threads. Then you're all set to just use another screw (swiped out of a junkyard is the best plan, since it has the same automotive-grade corrosion plating).

  • Otherwise, especially if you're slightly off-center, you may need to just gore up the threads a bit until the old junk is gone, and see if the threads will hold a bolt.

  • If you overdrill a bit, that's fine, just up-thread to the next larger metric or SAE hole size that is the correct size for a metric or SAE tap. Note how the fine and coarse thread bolts use different hole sizes.

All the above goes better if you block it on a drill press so it's square, and clamp or vise it down so it stays square and can't move. That's what the machine shop will do. 2/3 of the work is painstakingly blocking and clamping it onto the drill press so it's square and can't move.

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  • There actually exists "reverse drill bits", I've had some luck, after soaking the recalcitrant bolt with penetrating oil, in drilling using left handed drill bits (going counter clockwise). Sometimes just that would loosen the bolt or screw and it would back out. At least you are applying force in the direction you want, even if it doesn't bust it loose. – George Anderson May 16 at 2:27
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Seen those "easyouts" snap off making the task even harder...

The tool I use involves drilling into the bolt then hammering a hardened shaft which has special flutes cut into it into the hole. Then there are special nuts that slide onto the hardened shaft which turn the shaft and broken bolt.

Two points: drill centred and use the largest below the thread root depth.

Worked for me every time.

See this example: Blue-Point Screw And Bolt Extractor Set 25 Peice. Snap-On E-1020

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  • Not meaning to be too conversational here, but many years I was replacing an exhaust manifold on an old Buick V-8, snapped off a bolt, tried the easy-out, snapped it off just like you said! Ended up having to pull the head and take it to an awesome welding shop nearby. When I brought it in the guy asked me what was in the bolt? I said an easy-out, he just gave me the "eye roll". To fix it he heated it up red hot and then blasted it with pure oxygen, sparks flew but the cast iron head wasn't affected, he cleaned it up with a tap. All fixed, just had to share about the easy-out comment. – George Anderson May 15 at 21:33
  • The problem is mainly the bolt is sleazed. Without penetrating oil or heat, most bolt removers will break off also. Acetone and ATF in 50/50 mixture has been found to be the best. A good soak and a few taps/wacks does wonders. – crip659 May 15 at 21:48
  • @crip659 "bolt is sleazed" What is that exactly? :-) – JACK May 15 at 23:29
  • Bad spelling on my part. – crip659 May 16 at 0:54
  • @crip659. Is ATF = Automatic Transmission Fluid? – gatorback May 16 at 3:05

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