Broken Bolt !!
Discussion
Hi despite managing to remove exhaust manifolds without breaking anything!! taking off the warm up regulater and output elbow on top front of engine (2.8 cologne) 2 bolts securing ...the 1st one snapped !!! with little pressure...now only about 3/4mm of broken bolt stuck in the casing part of head?..Any advise please do not want to make worse than it is ,,,,,How can i get this out...
Stud extractors. If ever there was a tool thought to be some kind of cure for all ills, this one is it. In my 'umble experience, they work about one time in 20. Now this may be partly due to the fact that they're almost all churned out from monkey-metal in China, but that's not the real problem. Like taps and drills, they're fairly hard, in order for them to be able to bite into the thing you're trying to remove. Which makes them brittle. So too much force and they snap.
The principle is simple: you drill a hole down the centre of the snapped stud (or bolt) and screw in the extractor. Which is tapered, and has a spiral pattern cut into it to allow the extractor to grip the stud. Once a secure bite is obtained, you apply a small spanner (or tap wrench) and wind out the offending piece.
Thing is, by definition you are now trying to undo something of an even smaller diameter than the thing you broke in the first place. If there's that much force still gripping the broken bolt, it's unlikely that something smaller (and tapered, and brittle) is going to miraculously overcome said force. And it usually doesn't.
If the bolt or stud sheared when you tried to undo it, something is corroded or cross-threaded. The only time I have ever found an extractor to work is in the case of a bolt (or nut on a stud) that was over-tightened but NOT bottomed out. Usually, the head shears off the bolt, or the stud snaps either just below the nut or just where it exits the part it's screwed into. In these cases an extractor will usually work... but then again, in a lot of those cases you can unscrew the broken length with your fingers or a pair of pliers.
If you bottom-out a bolt and it shears, again an extractor will generally not work because the forces acting to lock the thread will exceed the torque that the extractor will accept.
I work with industrial x-ray equipment. It tends to get used outdoors in all weathers and over the years I've lost count of the corroded steel bolts in alloy castings I've had to remove. I don't bother looking for extractors anymore. I just file the broken end flat, centre-punch and drill out in stages, working up through progressively larger drills. Often as you approach the size of the bolt, the heat of drilling, plus maybe relief of stresses, permission of the gods, who knows... but the remains of the thread will often crack free and spin out with the drill. Other times, you can get to almost full-size and then collapse the remains of the thread inwards with a centrepunch. In the majority of cases the thread is undamaged, or maybe just needs chasing with a tap to clean it up.
Another option where available is to use a TIG torch like a blowlamp and apply very localised heat around the siezed bolt. Alloy expands quicker than steel and sometimes the bolt can be cracked free with judicious application of an automatic centrepunch to the periphery of the bolt.
Worst case scenario, you drill the bolt right out and Helicoil the damn thing!
The principle is simple: you drill a hole down the centre of the snapped stud (or bolt) and screw in the extractor. Which is tapered, and has a spiral pattern cut into it to allow the extractor to grip the stud. Once a secure bite is obtained, you apply a small spanner (or tap wrench) and wind out the offending piece.
Thing is, by definition you are now trying to undo something of an even smaller diameter than the thing you broke in the first place. If there's that much force still gripping the broken bolt, it's unlikely that something smaller (and tapered, and brittle) is going to miraculously overcome said force. And it usually doesn't.
If the bolt or stud sheared when you tried to undo it, something is corroded or cross-threaded. The only time I have ever found an extractor to work is in the case of a bolt (or nut on a stud) that was over-tightened but NOT bottomed out. Usually, the head shears off the bolt, or the stud snaps either just below the nut or just where it exits the part it's screwed into. In these cases an extractor will usually work... but then again, in a lot of those cases you can unscrew the broken length with your fingers or a pair of pliers.
If you bottom-out a bolt and it shears, again an extractor will generally not work because the forces acting to lock the thread will exceed the torque that the extractor will accept.
I work with industrial x-ray equipment. It tends to get used outdoors in all weathers and over the years I've lost count of the corroded steel bolts in alloy castings I've had to remove. I don't bother looking for extractors anymore. I just file the broken end flat, centre-punch and drill out in stages, working up through progressively larger drills. Often as you approach the size of the bolt, the heat of drilling, plus maybe relief of stresses, permission of the gods, who knows... but the remains of the thread will often crack free and spin out with the drill. Other times, you can get to almost full-size and then collapse the remains of the thread inwards with a centrepunch. In the majority of cases the thread is undamaged, or maybe just needs chasing with a tap to clean it up.
Another option where available is to use a TIG torch like a blowlamp and apply very localised heat around the siezed bolt. Alloy expands quicker than steel and sometimes the bolt can be cracked free with judicious application of an automatic centrepunch to the periphery of the bolt.
Worst case scenario, you drill the bolt right out and Helicoil the damn thing!
Guys thanks for all the advise much appreciated.....think I like the sound of Wedge1e 's drill out with a number of slightly larger dia drills...access is good....will let u know who it goes...replacing anything I remove with Stainless Bolts Nuts on refitting all ancilleries..good idea?
peterc67 said:
Guys thanks for all the advise much appreciated.....think I like the sound of Wedge1e 's drill out with a number of slightly larger dia drills...access is good....will let u know who it goes...replacing anything I remove with Stainless Bolts Nuts on refitting all ancilleries..good idea?
Don't forget that bolts are usually pretty hard too and will take the sharp edges off your drills if you drill too quickly (ie chuck speed). Using a cutting lubricant, ironically, can make it worse. You need to 'feel' the drill cutting and maintain that speed.Stainless bolts are a good idea as long as it's not a high-torque application because they tend to have lower tensile strength than normal ones. So manifolds, brackets, covers... all OK; clutch plate or wheel hub probably not so
Also watch out for 'galling' with stainless; where a new bolt and nut will lock themselves together absolutely rock-solid for no reason at all. You can just spin the nut on by hand but then find it won't come off!
Leave the stud extractors on the shelf in the shop where they belong. Before you try anything else, read this article:
http://www.pumaracing.co.uk/ToolUse.htm
http://www.pumaracing.co.uk/ToolUse.htm
If you are going to be using an electric drill with a reversing capability then you could try a left-hand drill see <http://www.thesitebox.com/Category/4158/left-hand-jobber-drill.aspx> and other places on the web.
If you drill into the stud using a normal drill then the tendancy is to tighten the stud, with a left hand drill the tendancy is to unscrew it.
Russ
If you drill into the stud using a normal drill then the tendancy is to tighten the stud, with a left hand drill the tendancy is to unscrew it.
Russ
I had the bolt securing the inlet manifold gasket seal snap. It was flush with the block. I got a small pointy file and spent 15 mins carefully rubbing a channel in the end of the remaining bolt (whilst whistling an amusing tune to myself) which became a big enough slot to fit a screwdriver in. It then screwed out. I had left it overnight soaked in penetrating oil which may have helped. I wouldn't use heat. Very careful drilling would be my last resort.
My advice from rebuilding my V8 is be very careful replacing stainless bolts. They seem to need less torque than normal bolts and are easy to strip the block threads. Also, the kits you buy off ebay do not always contain the correct length bolts so do not throw away your old bolts. I ended up shot blasting a lot of mine and they looked quite good.
My advice from rebuilding my V8 is be very careful replacing stainless bolts. They seem to need less torque than normal bolts and are easy to strip the block threads. Also, the kits you buy off ebay do not always contain the correct length bolts so do not throw away your old bolts. I ended up shot blasting a lot of mine and they looked quite good.
GRIFFONMARK said:
I ended up shot blasting a lot of mine and they looked quite good.
Been there, done that, as a last resort. You have to make sure you get all the blast media out of the thread (I'm sure you did!).... but the other issue is that you can produce a nice abrasive surface on the thread - effectively a file! Probably not an issue on a 3/8" UNC holding an exhaust manifold, but you would hope the guys who strip and rebuild aero engines don't do it that way (they don't, at least not in any of the plants I visit )The other issue is that you can strip any plating (eg cadmium, zinc) that the bolt may have had... but if it's that bad you need to blast it, it's probably irrelevant
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