Sheared bolt ideas please!

[salar]

I have been overhauling a late '90s Mercury 3.3 2-stroke outboard and as you might imagine, a lot of those pesky M6 stainless bolts are screwed directly into the aluminium castings. Two in the steering collar have sheared. They are stuck so fast that I have broken off a bolt extractor in them both. Final solution is to drill out, but I now have a very hard thing right where I want to drill. Will anything drill though a bolt extractor? I would have thought that it is as hard or harder than a drill. Replacing the casting would cost more than the motor is worth, at Mercury prices. Any suggestions or ideas please?

 

[coopec]

OMG! I thought I was the only that does things like that.

Have you priced a new motor?

 

[TRH]

Hi a Picture would help,

 

[sgr143]

Spark machining (Electro-discharge machining) would work, but I doubt you'd get the whole motor into an EDM machine... If the offending piece is separable (though it's probably your problem bolts that are holing it in place), you might find an engineering workshop that could do EDM for you.

 

[Yosilas]

I had this problem with a motorcycle gearbox, a man by the name of Roland welded an Allen key to the flush broken stud, this also had the effect of loosening the bond and it was only hand tight in its removal. He used an arc welder.

 

[TRH]

If you have a wide flange round the bolt,you could try to fit a reamer and take the bolt out and fit a helicoil

 

[MagicalArmchair]

If anything is sticking proud, you could try some of the things I did below when I did similar with my exhaust elbow bolt?

Remove a sheared off exhaust elbow bolt - Triola - Albin Ballad #50

 

[lw395]

Lots of stuff on youtube etc about using 'alum' to chemically remove steel from ali.

 

[rogerthebodger]

You can use alum to dissolve the steel extractor from the broken stud.

Once you have removed the extractor you can drill out the broken stud.

 

[salar]

Hi a Picture would help,

The casting is off the engine now. One bolt has sheared flush with the casting. The other sheared further up which you would think was a good thing, but even two nuts locked up tight didn't help me shift it, the threads stripped. @coopec pointed me to a good idea to drill out with a hole cutter, if I can find one small enough for a M6 bolt.

 

[salar]

If anything is sticking proud, you could try some of the things I did below when I did similar with my exhaust elbow bolt?

Remove a sheared off exhaust elbow bolt - Triola - Albin Ballad #50

An interesting read - thank you. Unfortunately the M6 bolt is quite small and I think extra force would make it shera again. It is a possibility on one bolt but the other is flush. I learned something from you about that stud extractor though!

 

[lw395]

Heat and oil may get the longer one out.
Rather than the old 'two nuts', I would put the stud in the vice and turn the casting.

The one that has snapped sort, I would use a dremel to grind a pit in the centre of the stud then drill it. Lefthanded drills will probably get that out leaving the thread usable. If not, helicoil. Or tap it M7 maybe.

 

[vyv_cox]

OMG! I thought I was the only that does things like that.

Have you priced a new motor?

Those diamond hole cutters are something else! If it took him an hour to get through with a 6 mm one I really would not like to do it with anything much bigger!

 

[Boater Sam]

I would drill from the other side. Use heat then use stud extractor or even a normal drill bit from the back side.
The best stud extractors are like left hand reamers, better than the coarse thread horrors that I always snap.
Welding a HT screw on does work but you need a steady hand.

 

[cherod]

as Yosalis said, weld something on / over , any weld , ( mig tig stick ) it has the added advantage of puting heat into the nut which helps ( contraction / expansion )

 

[cherod]

I would drill from the other side. Use heat then use stud extractor or even a normal drill bit from the back side.
The best stud extractors are like left hand reamers, better than the coarse thread horrors that I always snap.
Welding a HT screw on does work but you need a steady hand.

" steady hand " ,, well you ( or someone ) needs to be able to weld , but it is the way .

 

[northwind]

The casting is off the engine now. One bolt has sheared flush with the casting. The other sheared further up which you would think was a good thing, but even two nuts locked up tight didn't help me shift it, the threads stripped. @coopec pointed me to a good idea to drill out with a hole cutter, if I can find one small enough for a M6 bolt.

View attachment 93574

Now you have the bit free, soak it in either penetrating oil or in diesel, leave for a couple of days then apply heat to the Ali it should help to remove it.

 

[RichardS]

The studs have the great advantage that they appear to be open at both ends.

The one which is flush can simply be drilled out, ideally using a left-hand bit, as the bit used gets bigger, it will come out or can be re-tapped if there is still some bolt left embedded when you have drilled as large as you can without damaging the thread.

The one which is sticking out should be heated with a gas torch until it is very hot and the removed with external stud extractor, Stillsons or locked nuts. You need to get it really hot, several hundred degrees.

Richard

 

[salar]

Thank you @lw395, I put the projecting stud in the vice and turned the casting and out she came.

The bolt sheared flush is the remaining problem. I can't drill from the other side, there isn't sufficient clearance and the casting is about 175mm long.

As I posted originally, I can't drill it out conventionally because I have snapped off a bolt extractor in it so it is too hard to drill out. From all the helpful suggestions received so far, I think my best option is to use potassium aluminium sulphate. Failing that, a diamond hole saw if I can find one small enough. Only one to go now though!

 

[penberth3]

The casting is off the engine now. One bolt has sheared flush with the casting. The other sheared further up which you would think was a good thing, but even two nuts locked up tight didn't help me shift it, the threads stripped. @coopec pointed me to a good idea to drill out with a hole cutter, if I can find one small enough for a M6 bolt.

View attachment 93574

Is that your broken stud extractor off-centre in the sheared stud? The next size up would have been a good idea, and on the centre of the stud, but too late now. Also looks circular, I guess its the left hand threaded carrot type? So harder to remove than the tapered square type.

Because it's off centre you've got room to attack the remaining stud with a Dremel. You could even start by drilling a small hole or two. You might then be able to grind enough stud away to get a grip on the broken extractor, maybe tap it with a centre punch to loosen it.