Sheared bolt ideas please!

[RichardS]

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.

I agree.

I had not realised that the depression is the remains of the stud extractor but thought that was just an off-centre drilling. It is too small for that size of stud although easy-outs are notoriously unreliable and, after failures of my own even using the correct size, I now always reverse drill out and re-tap. That being the case, I would drill out from alongside the broken extractor and try and undercut it.

Richard

 

[Beneteau381]

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.

I would go with that. Small drill to one side, very slowly slowly, heat, tap, centre punch to one side, when people adk me I always say its a culmination of lots of things, but mostly heat!

 

[mikegunn]

As SGR suggested, EDM (electro discharge maching) is the way to go. There must be a jobbing shop not too far from you who could handle the task. EDM is a very accurate process and can remove the bulk of the stud and extractor without subjecting the component to undue mechanical or heat stress. You should finish up with a clean hole of tapping drill diameter and then be able to pick out the remainder of the stud's thread. Re-tapping will clean up the female thread.
Mike

 

[steve66]

Put the bracket in a vice....heat up the casting around the stud as hot as you can.......then spray it with water or preferably carb cleaner. Repeat a few times and you will find it will unscrew easily....failing that soak it in Coca Cola

 

[salar]

Nobody else recommending dissolving with alum? It seems a low effort option to me, particularly as this is a small casting and a M6 thread so not much to fizz away. The top of a sheared M6 is a very small work area to fiddle about with (hence the off-centre drilling!)

 

[rogerthebodger]

The top of a sheared M6 is a very small work area to fiddle about with (hence the off-centre drilling!)

I have managed to drill out a M6 stainless stud in Aluminum, I found using a long 5mm drill bit in a battery drill allowed me to bend the drill bit to compensate any runout and keep the bit drilling in the center of the stud.

Not so easy with a shorter drill.

 

[ghostlymoron]

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.

Why not use a centre tap to provide a start for the extractor?

 

[salar]

I have managed to drill out a M6 stainless stud in Aluminum, I found using a long 5mm drill bit in a battery drill allowed me to bend the drill bit to compensate any runout and keep the bit drilling in the center of the stud.

Not so easy with a shorter drill.

Not so easy with a snapped off drill in the stud either! If I can get a long enough 5mm metal drill I could possibly drill out from the other side.

 

[rogerthebodger]

Not so easy with a snapped off drill in the stud either! If I can get a long enough 5mm metal drill I could possibly drill out from the other side.

That's where the alum comes in to remove the snapped off drill.

You then either use a center punch to peen the hole closed and to mark the new center to drill adjusting the angle of the long drill to keep it in the middle.

 

[lw395]

Why not use a centre tap to provide a start for the extractor?

It looked like there was already a pit in the face of the stud, off centre. Using a dremel, you can move that to the centre.
I didn't clock that it was actually a broken extractor.
I have never, ever had any success with the type of stud extractor which threads into a broken bolt or stud.
A lot of the problem IMHO is that they expand the bolt as they thread in, tightening the grip of the bolt in the hole.
The corrosion is probably already putting pressure on the bolt. If you can release the pressure by drilling the 'meat' out of the core of the bolt, then it may undo. The LH drill method keeps removing material until the drill catches in the bolt and undoes it. It puts some heat in too.
I've heard of people using acids to dissolve the corrosion products between bolt and ali, with unproven tales of success. YMMV.

 

[penberth3]

….I have never, ever had any success with the type of stud extractor which threads into a broken bolt or stud.
A lot of the problem IMHO is that they expand the bolt as they thread in, tightening the grip of the bolt in the hole.
The corrosion is probably already putting pressure on the bolt.....

A good point. Are stud extractors even meant to work on badly corroded threads? There is a splined type which doesn't expand the bolt, but these can also break!

 

[salar]

That's where the alum comes in to remove the snapped off drill.

Won't the alum dissolve the stainless steel bolt or will it only dissolve the hard steel drill/extractor?

 

[rogerthebodger]

Won't the alum dissolve the stainless steel bolt or will it only dissolve the hard steel drill/extractor?

Mr Google says yes which is very interesting

Will alum dissolve stainless steel? - Google Search

 

[salar]

Mr Google says yes which is very interesting

Will alum dissolve stainless steel? - Google Search

That's currently Plan A with 500g of alum on the way from Lancashire.

 

[rogerthebodger]

That's currently Plan A with 500g of alum on the way from Lancashire.

Please do let us know how it works as it could solve many problems where stainless steel is stuck in aluminium.

 

[snowbird30ds]

With the casting off it looks a doddle, tig weld a larger nut over it, let it cool down then heat the aluminium, should bring bolt and extractor out together.
Get sheared bolts out at work like that a lot.

 

[salar]

With the casting off it looks a doddle, tig weld a larger nut over it, let it cool down then heat the aluminium, should bring bolt and extractor out together.
Get sheared bolts out at work like that a lot.

Well the Alum didn't work so I tracked down a local chap with a delicate welding hand and tonight he welded an oversize nut onto the stud and up she came! So happy....By the way the Nextdoor app/site is so useful, in addition to finding my new welding friend I have exchanged a lot of useful materials for boating, gardening and other projects. You would be amazed at what is lying around only streets away.

 

[Crazy-Diamond]

I used a Dremel to remove a snapped stud. I think the bit I used was carbide tipped. It took quite a while, but was very successful in the end. I liked using the Dremel as it is small and easy to move around. I eventually had all the metal inside of the bolt removed, and the threaded outer metal came out in a long helix! Must have taken 2 hours of slowly whittling away, but I could see it was working and I'd get there in the end!

 

[salar]

I used a Dremel to remove a snapped stud. I think the bit I used was carbide tipped. It took quite a while, but was very successful in the end. I liked using the Dremel as it is small and easy to move around. I eventually had all the metal inside of the bolt removed, and the threaded outer metal came out in a long helix! Must have taken 2 hours of slowly whittling away, but I could see it was working and I'd get there in the end!

Blimey! Two hours... there was a guy on Youtube who ground out a tap with a diamond hole drill and that only took an hour, 30 seconds at a time and cooling in between. Note for next time...the welding job was done in about 15 minutes, although it took me about two weeks to find someone to do it so on balance your method was quicker ?

 

[KAM]

For future I can reccomend diamond dremel bits sold by Lidl. It was only about £5 a set. I broke a stud extractor trying to extract a sheared screw. I thought it would be a spark eroding job but it was relatively easy to grind out the broken extractor with a fine diamond tip. I also found the diamond tool very accurate for making centres when drilling out broken screws. Well worthwhile having in the tool kit.