Removing stainless steel bolts from aluminium?

[VicS]

Advice is being sought on this topic via the owners association message board by one of our members.

Specifically they are 6mm bolts (or set screws I think) holding the thermostat cover on a small outboard. The heads have already been wrung off and the cover removed but leaving about 3/8" to 1/2" of thread accessible. It may therefore be possible lock a couple of nuts on to them.

Suggestions already made include tapping/smacking the ends with a hammer, heating them to red heat or warming the whole lot up to a more modest temperature. They have been soaked in Plus Gas penetrating fluid.

Do any of the experts on the forum have any further suggestions. Obviously the owner does not want to risk damaging the engine.

 

[Ben_e_Toe]

Heat is the only way (in my limited experience) that I have found of removing stainless steel from aliminium. That said the fire risk in this case may be unacceptable.

 

[tross]

Hi,

Just had the pleasure of this x4 ! I had 2 go on the leg to power head joint and 2 go on the exhaust tube.

1st I used my MIG welder to build up the remaining of the studs so I could get a purchase on it - that worked for 1 the others just broke the stub further down. 1 down 3 to go

2nd Ground off the studs to a little way off the casing and VERY carefully strarted with a small drill drill out he stud - I finished with a 5.0mm drill and then taped a 6mm thead in to that 3 down 1 to go

This is a right b*****d I am going to to drill this one out and fit a helicoil ( tonight's job).

When I rebuild this I am going to use zinc chromate on the screws to stop this happeninng in the future.

Good Luck !

 

[boatmike]

Yep! Its a [--word removed--]! Problem with drilling out is you need to clamp the thing on a milling machine or bench press and carefully centre drill on the precise centre of the bolt first. Drilling by hand the drill will wander into the softer aluminium. If you have enough left for 2 nuts great. You need to apply heat to the area locally using an oxy acetylene torch or similar while working the bolt loose without snapping the rest off! Don't do this without a full strip down of the part though and eliminate the possibility of a fuel fire by cleaning thoroughly first.

 

[VicS]

Thanks for the replies so far.
I have already stressed that it is one job where brute force and ignorance are not appropriate. I had not considered the fire risk but in this case I think the engine has not been used for a good while so should be free of significant quantities of petrol. It's a point well made though.

In a day or two I'll post a link on the OA message board to this thread.

 

[Norman_E]

You do not need to worry about significant quantities of petrol, you can always tell if you have a large amount. A small quantity of petrol, vaporized in a confined space is all you need for a nasty explosion.. If you are going to apply heat from a blow lamp, remove the fuel system and carburettor completely before hand. I agree with other posters that heating the studs is the most likely route to freeing them. The problem is that the corrosion products of aluminium alloy swell up and the studs become very tightly locked in place. Heat expands the alloy and gives you some chance of getting them out with a mole wrench.

 

[roger]

You can get the same problem with life line stanchions in Ally holders. A suggestion I have read is to build up a dam round the lip of the holder and fill the space with Coca Cola. (its quite a strong acid). I have no idea whether it works.

 

[VicMallows]

I noticed the other day in our local Chandler that LOCTITE now sell an aerosol freezer/lubricant aimed at this problem. Somehow, FREEZING doesn't seem logical, but I guess if you can manage to freeze the bolt/stud without freezing the nut/tapped-hole it could be effective. Anyone tried it??

Vic

 

[Avocet]

If you've a bit poking out, try the two nuts first. Try tightening as well as loosening. If you get ANY movement at all, give it all a good squirt of plus gas (or diesel works quite well) and leave them overnight. Have another go at just working it backwards and forwards. Another thought would be to weld a long bolt (or similar) at 90 degrees to the stub that's poking out. The heat of the welding can sometimes free things off and the long bolt then the stub acts as a good lever for screwing them out. Obviously, you need to have faith in the welder but it's harder to damage the surrounding aluminium than you'd think!

Good luck! Unfortunately, there are no easy solutions!

 

[fireball]

Just to add my 2pence .... having had exhaust studs sheer off flush on my MG ... we carefully drilled the center out - starting with a pilot and then putting a bit through just smaller than the shaft of the stud. Then having purchased some of these reverse thread screws (they're tapered bolts with big screwthreads and a square end) we managed to unwind the studs and replace with some new ones! Typically I've not needed these tools since /forums/images/graemlins/frown.gif

I can post a photo if anyone is really bothered...

 

[fisherman]

If you can get a hole in the stud, try an 'Easy-Out' (TM). Buy them any tool shop/motor factor.

 

[fireball]

Ok - I was getting some other photos off the camera ... so took one of the stud extractor for your enjoyment! /forums/images/graemlins/laugh.gif

The beauty of these are that it doesn't matter how much you turn it anticlockwise it will just dig in and grip firmer...

 

[Cruiser2B]

Along the same lines - you could put a nut on and weld it to the stud. The heat from welding may un-stick it.

 

[VicS]

I have always been under the impression that Easy-Outs were not really much use on these small sizes. The core diameter of a 6mm bolt is only 4.7 mm so there is not much metal there to play with but if they get sheared off flush in the next round of attempts then perhaps its the next thing to try before drilling and retapping or filling helicoils.

If my old dad was still alive he'd have them out in no time.

 

[fireball]

True - my studs were around 9/10mm ... so plenty to get hold of ...
I do have the smaller one (somewhere) and I think it'd remove an M6 no prob ... I'd probably try the heat route first though...

 

[andyball]

from years of removing broken/seized screws on motorcycles..... ( always alum casings )

Heat,heat,heat ! A blowtorch is adequate if casing not too large - don't apply huge force until the ally is really,really hot. That is it's pinging (you'll know) , this takes time (relatively) with a blow lamp. Heat the casing-not the stud. & be sensible if using welding torch not to burn it away.

99/100 tapered extractors for really stuck threads in alum = no good. Just expands the remains of the stud even tighter. Parallel extractors rather better - but not really needed if you have some thread exposed.

you can drill these things out by hand, but it takes practice to get them just right. Naturally much easier if you don't wait 'til the stud broken off unevenly below the face of the housing. Smallish mistakes - then a thread insert will sort it out.


At the risk of repetition : use heat! Most times, drilling only necessary because someone tried to get the thing out using some other method, or using a blowtorch & not getting the casing hot enough.

 

[Norman_E]

[ QUOTE ]

Ok - I was getting some other photos off the camera ... so took one of the stud extractor for your enjoyment! /forums/images/graemlins/laugh.gif

The beauty of these are that it doesn't matter how much you turn it anticlockwise it will just dig in and grip firmer...

[/ QUOTE ]

Every time I have tried one of these things it has either broken because it was too brittle, or it has expanded the remains of the stud and jammed it even tighter. On a 6mm stud you will need to use quite a small one, and it is very doubtful if it will be strong enough to get the stud out if it is siezed into aluminium.

 

[ex-Gladys]

In my experience E-Z-Outs tend to break easier than bolts, then you're stuck with a piece of bust off hardened steel to get out....

 

[tcm]

yep, but for a 6mm stud he will need to hold it and a drill in a jig/machine to get a decent and central starting/pilot hole, then use the very smallest stud extractor on a socket wrench and possibly consider the delicate use of a short scaffold pole for extra leverage.

Before that, though, I'd try filling the available thread with locknuts - not just two locknuts - to reduce any tendency to bend the (quite thin, 6mm) stud. Clamp the whole thing with wood blocks in a vice or even in a (say) concrete hole if no suitable vice available. Again, you need super leverage, so socket wrench or several identical ring spanners if it's a long stud, then a scaffold bar gives the extra leverage needed.

 

[Avocet]

Is there enough casting thickness to drill the whole thing out and re-tap the holes to take an M8 thread?