Avocet
Well-known member
Just seen this too.
http://www.northerntooluk.com/clearance/...rew%20Extractor
Pricey for one job though!
http://www.northerntooluk.com/clearance/...rew%20Extractor
Pricey for one job though!
Removing stainless steel bolts from aluminium?
- Thread starter VicS
- Start date
tcm
...
Urg, drilling and tapping and helicoils
Um, this is absolutely last ditch and on a small outboard things will be tight. It would be well into the realms of needing proper engineering gear. Trying the locknuts option would be first for me.
I would imagine that the minor diameter of an m8 thread is 7mm, making it possible but with not much room for error at all.
Much bettter (if he locknut option doesn't work or snaps the stud off at the surface) to drill internally with say up to 4.5mm and use a v small stud remover.
In any event, to drill out the stud it would need a pilot hole first - so may as well then use stud remover.
I don't think it would work to try and go in first with (say) a 6.5 mm drill to take the entire thread out - defelction of the drillbit would encourage the drillbit out into the softer aluminium, imho.
If there isn't the room for M8 but the stud comes out badly then helicoiling is an option, but again really needs an engineering shop with Helicoil gear. The helicoil insert goes into a slightly oversized (for m6 in this case) helicoil-tapped hole and a coilded insert put in (it's a bit like a spring) and returns the thread to M6.
Um, this is absolutely last ditch and on a small outboard things will be tight. It would be well into the realms of needing proper engineering gear. Trying the locknuts option would be first for me.
I would imagine that the minor diameter of an m8 thread is 7mm, making it possible but with not much room for error at all.
Much bettter (if he locknut option doesn't work or snaps the stud off at the surface) to drill internally with say up to 4.5mm and use a v small stud remover.
In any event, to drill out the stud it would need a pilot hole first - so may as well then use stud remover.
I don't think it would work to try and go in first with (say) a 6.5 mm drill to take the entire thread out - defelction of the drillbit would encourage the drillbit out into the softer aluminium, imho.
If there isn't the room for M8 but the stud comes out badly then helicoiling is an option, but again really needs an engineering shop with Helicoil gear. The helicoil insert goes into a slightly oversized (for m6 in this case) helicoil-tapped hole and a coilded insert put in (it's a bit like a spring) and returns the thread to M6.
tcm
...
Another idea - don\'t remove studs but make special nuts
With half an inch to 3/8 of stud showing, another option is to get some suitable extra-long nuts made. This could be quite cheap.
The local engineering shop starts with s/s 10mm across flats hex bar (ie what you'd make m6 nuts with) .
Then they turn down end 12mm length to (say) 8.2mm outside diameter, cut off at 20mm length, drill and tap that piece of hex bar to give a "long recessed nut".
Open up the 6mm hole in cover to just accept the 8.2mm diameter.
There should be room to shim with a washer, and 12mm of thread would produce a good solution (twice the thread area of an ordinary nut) and hence not need loads of torqueing up. Just ornery removable locktite on the new nut thread.
I like this more than "loads of heat" options.
With half an inch to 3/8 of stud showing, another option is to get some suitable extra-long nuts made. This could be quite cheap.
The local engineering shop starts with s/s 10mm across flats hex bar (ie what you'd make m6 nuts with) .
Then they turn down end 12mm length to (say) 8.2mm outside diameter, cut off at 20mm length, drill and tap that piece of hex bar to give a "long recessed nut".
Open up the 6mm hole in cover to just accept the 8.2mm diameter.
There should be room to shim with a washer, and 12mm of thread would produce a good solution (twice the thread area of an ordinary nut) and hence not need loads of torqueing up. Just ornery removable locktite on the new nut thread.
I like this more than "loads of heat" options.
fireball
New member
Re: Another idea - don\'t remove studs but make special nuts
Hmm - the internal stud extractor not recommended then ... /forums/images/graemlins/frown.gif Ah well ...
Just remembered the other tool I have is another stud extractor that uses a grip wheel on a cam - turns into the shaft and locks on - further turning just tightens its grip - still need the heat to release the pressure on the thread though...
Hmm - the internal stud extractor not recommended then ... /forums/images/graemlins/frown.gif Ah well ...
Just remembered the other tool I have is another stud extractor that uses a grip wheel on a cam - turns into the shaft and locks on - further turning just tightens its grip - still need the heat to release the pressure on the thread though...
Avocet
Well-known member
Re: Another idea - don\'t remove studs but make special nuts
Just another thought, I take it the back of the assembly isn't flat enough for you to drill right through and use a nut and bolt by any chance? Long shot!
Also, re-tapping to M8 wil lalmost certainly leave you with a poor thread (drill wandering, bits of old thread in the way etc) but in my experience you can often get away with it because you won't need anything like the clampng force you could get out of a properly formed 8mm thread!
(how's that for a bodge!)
This is pretty last-dtich stuff. As has been said, Try heat first!
Just another thought, I take it the back of the assembly isn't flat enough for you to drill right through and use a nut and bolt by any chance? Long shot!
Also, re-tapping to M8 wil lalmost certainly leave you with a poor thread (drill wandering, bits of old thread in the way etc) but in my experience you can often get away with it because you won't need anything like the clampng force you could get out of a properly formed 8mm thread!
(how's that for a bodge!)
This is pretty last-dtich stuff. As has been said, Try heat first!
VicS
Well-known member
Thanks for all the suggestions. Heat seems the best approach as I suspected. Small Easy-outs suffer from the problems I thought they would, ie are likely to expand small sizes so thay they grip even tighter and themselves are easily broken off then making drilling out even more difficult. Also I would be wary of tricks to increase leverage (scaffold poles etc) as that will increase the risk of breaking off the bit we can get hold of at present.
The recessed nut idea I liked but if the engine in question is anything like my own there just won't be enough metal spare to do it. The lack of metal may also make drilling out for a larger size impracticable.
Getting the thing onto a drilling machine may not be feasible either because the poor owner won't want to dismantle the engine any further as he has already had enough trouble with these bolts without trying to undo any more! Working on the undismantled engine will also limit the heating that can be done unfortunately.
I fear the treatment with Cola will not work now that it has all been soked in Plus Gas as that leaves an oily residue, it's perhaps something to try first another time.
However I will now post a link to this thread on our message board
The recessed nut idea I liked but if the engine in question is anything like my own there just won't be enough metal spare to do it. The lack of metal may also make drilling out for a larger size impracticable.
Getting the thing onto a drilling machine may not be feasible either because the poor owner won't want to dismantle the engine any further as he has already had enough trouble with these bolts without trying to undo any more! Working on the undismantled engine will also limit the heating that can be done unfortunately.
I fear the treatment with Cola will not work now that it has all been soked in Plus Gas as that leaves an oily residue, it's perhaps something to try first another time.
However I will now post a link to this thread on our message board
roger
New member
Studs, taps and stud extractors break off in castings quite often in engineering shops. The standard engineering solution is spark erosion. With a bit of luck you could get your local engineering workshop to do the work - might be pricey though.