help! - snapped bolt stuck in aluminium casting

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kashurst

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Help - bit of a disaster, I have managed to snap the head off a bolt whilst trying to undo it from an aluminium alloy cylinder head. Most of the bolt is still sticking out, Tried molegrips and heat but no luck. I don't want to take the head off and have it machined out unless absolutely necessary. Any suggestions gratefully received.
 
Try tapping it lightly from all directions whilst at the same time dribbling a drop of diesel down the thread. Might work.
 
Tap and die set. Put a thread on the exposed bolt shank. Run a big hex nut down the thread then get someone with a mobile welder to spot weld the top of the bolt/nut. Then use a good socket set after soaking in release oil, perhaps overnight?
 
Highandry is suggesting more or less the same way I would tackle this except I would weld a flat washer on whatever is left of the bolt then weld a nut on the washer. Same idea different implementation.

Heat from welding may help move the bolt but be careful not warp the head ! !

73s de
Johnth
 
sheered bolt

had to do a lot of this when was apprentice.
if the above fails an alternative is to cut the protruding thread off to as near flush with its housing as you can.
then drill a pilot hole into the center of the thread, maybe half the diameter of the original thread. that usually has the effect of freeing the remaining bolt. i presume the casing is cast iron or steel.
lots of oil and slow. as its ally it should free easy.
 
kashurst said:
Help - bit of a disaster, I have managed to snap the head off a bolt whilst trying to undo it from an aluminium alloy cylinder head. Most of the bolt is still sticking out, Tried molegrips and heat but no luck. I don't want to take the head off and have it machined out unless absolutely necessary. Any suggestions gratefully received.
Click to expand...

Has it turned at all, or did the head snap off when you were trying to start it turning? The former is definitely better news!
 
Freeing a snapped bolt

I would be inclined to try the arc welder idea. Be very careful but I think you will find that application of the welding rod on top of the stud will provide rapid heating of the stud so break the corrosion bonds. The welding will also aid in getting a grip with molegrips.
If you are reluctant or unable to hit it with a welder. You could try gentle warming of the cylinder head. Then hit the stud with one of those instant freeze type products in pressure can available from electronic stores. This will be far less agressive and so may not work. If all else fails drill the hole down the middle. Depending on how accurate your drill location if an easy out doesn't work you can drill right out to near the outer edge of the bolt. The heat will almost certainly release what is left of the bolt. good luck olewill
 
horrible job

kashurst said:
Help - bit of a disaster, I have managed to snap the head off a bolt whilst trying to undo it from an aluminium alloy cylinder head. Most of the bolt is still sticking out, Tried molegrips and heat but no luck. I don't want to take the head off and have it machined out unless absolutely necessary. Any suggestions gratefully received.
Click to expand...
If you have room and the shaft has a large enough diameter grind the shaft flat, centre punch, pilot hole then increase drill size as to not damage threads, steel bolts chemically react to aluminium leaving a whitish powder which causes the seizure. If you damage the thead a helicoil may be sufficient. all the best with your plight.
 
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I'd go for the drilling scenario. It's always worked for me and is a lot gentler.
Just test drill a hole with your pilot drill bit first on some scrap. If it's a poor drill or has been re-sharpened it may not drill concentrically with the centre punch mark and then you have to be very careful not to accidnetally drill out the threads at on side of the hole. Nightmare.
 
Before going to the machining/welding route, I suggest that you try a good penetrating oil - and leave it at least a day to give the stuff time to work down into the thread. Gentle heat is good too, as steel has a different expansion coefficient to aluminium.
 
its a hard one this i had three 6mm shear off taking the leg of a yamy 5 hp had to go with careful drilling and the tapped with quarter inch imperial threads the threads were a bit shallow <but they did hold>as quarter is only a bit bigger than metric but used plenty of oil while tapping and kept cleaning swarf out till plug tap bottomed out

best of luck

I didnt put full tork on when titening em but put tab washers on to stop them coming loose
 
If you have a decent length of bolt why not try a stud extractor, much better than mole grips. Driling a hole and using those bolt removal tools is a bit risky, you must drill the hole right in the middle which is hard with a hand drill and then hope the extractor hold and doesn't break off in the hole. I assume you got the bolt half way out so I reacon a stud extractor will do it something like this:
http://www.justoffbase.co.uk/1-2-Sq...a8b3e9237df41e29.e3eTaxiNaN0Te34Pa38Ta38Qbhf0
 
You could try this method & no welding required. Assuming the thread on the stud is still good
take two nuts of correct size. Screw one onto stud & then the other and lock them together preferably with ring spanner if you have them. You can now try to get the stud to shift by unscrewing the botton nut against the top locked nut. Try it the other way then back again.
It might just work.

Let us know how you got on. Have a few other ideas which may help.
 
I used to have a Norton Commando with alloy chain cases and bronze bushes shrunk in as well as steel bearings. I struggled changing bushes and bearings until I was given a copy of the owners club instruction video which showed how removal of these things were done. Heat. In short I was being way too timid in the application of heat which they did with a propane torch. You heat until they drop out

And the chain cases were much lighter alloy castings than a cylinder head and so much more vulnerable to distortion.

PIf it were mine I would put the head in SWMBOs oven turned up full blast. Let it soak. Then try the mole grips.

P.S. Just seen that the head is still on the engine. Dont know an effective way od dealing with it in situ.
 
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I have no direct experience of this particular problem but did successfully conclude something similar by heating the two pieces metals concerned whilst covering them with oil. The expansion and contraction caused by the heat allowed oil to penetrate sufficient enough to enable me to free them.

I'm sure there are those more qualified than me to comment if this might work or not. On saying that, if it was that simple I'm sure someone else would have mentioned it by now!!!

Good luck though.
 
A bit surprised that no-one has suggested tapping the sheared off bolt into the head slightly before starting to undo it. This can often release whatever is binding the two together.
 
Mmmm, been thinking about this bolt that has snapped on Kashurst. Could it be that the aluminum head has corroded in the bolt hole and “grabbed” the bolt with that white and powdery stuff when it isn’t cementing bolts in place. Could there be a chemical to just melt the stuff away. I wish !

If this is the case, tapping remains of the bolt from side to side while trying to move / remove the white corrosion may be the thing to try, as well as all the above, heat lube etc.

I had to have a snigger at the thought of someone trying to drill out by hand something hard from something soft. Difficult or what!

Has anyone else tried diamond burrs in this sort of situation. I had a broken roll pin to remove recently, worked a treat. There are flexible drives too, good for those difficult to get at little bu**ers.

73s de

Johnth
 
I would agree with KeithH before any welding soak it in duck oil, 3in1, WD40 or whatever other releasing oil for hours and keep re-applying the oil then try using stilsons these are usually used by plumbers but widely used in engineering the advantage of these is as you apply effort on the handle the jaws of the stilsons tighten. Try tapping the top of the bolt with a hammer and then tightening the bolt if it moves apply more oil and try un screwing it but keep put the releasing oil in..............buy the way are you a religious person!!!!!!!!!
 
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