exhaust clamp stud removalI

[Dookbob]

I,m having a little difficulty removing the exhaust clamp studs from the horizontal head. It,s on a badly neglected M600 that I am restoring. I got the nuts off with my usual trick of heating them to cherry red then unscrewing while still hot. One of the studs is badly corroded, the other needs changing anyway. I don't want to shear off these studs if I can help it. I have locked two nuts onto the stud and heated the stud to cherry red but it won't budge. I have left it to soak with WD40 for a day or two, then heated again, but still won't budge. I have heated ( with oxy acetylene torch ) the surrounding aluminium, still won't move. If they break off leaving a bit showing I can weld a nut onto them, but if they break off flush I am stuffed. don't want to get into a spark erosion situation. Has anyone got any suggestions before I go any further?

[Nottsbiker]

I'd have thought that heating the stud would cause it to enlarge making it harder to remove, but then you said you'd also heated the surrounding aluminium which expands at a quicker rate so you should be ok although I'd have tried to keep the heat away from the stud.

Have you tried giving the stud a few smart hits end on with a hammer to try and break whatever is sealing it in. Obviously do this on the nuts or you'll muller the threads.

[utopia]

Have you tried sharp blows with a hammer and punch on the end of the stud, to jarr the threads ?
Even better if you can keep some torque applied to the stud while hitting it at the same time.
Since you've already fitted the nut and locknut you'll have no worries about damaging the end of the stud in the process.
Also, perhaps a better penetrating oil....plusgas maybe ? ...vinegar is also sometimes recommended, but I've never tried it myself.
And I'm wondering if that spray that plumbers use to freeze water pipes can be used to shrink the stud, in conjunction with heat to expand the alloy head. You could consider some sort of heat shield on the base of the stud to maximise the temp difference between it and the head.
Thinking a little further outside the box, I'm also wondering if you could somehow use the hammer action of an electric drill to jarr the threads, maybe using some sort of inverted cup in the chuck which sits over the end of the stud......???
I guess gravity isn't helping with the penetrating oil if the engine is still in the frame. Is there any way you could get the engine upside down.
Even further outside the box...could you drill a tiny hole angled inwards toward the stud, to supply penetrating oil to the base of the threads...? Though that's a weird one, I accept. Perhaps a better plan would be to drill the hole down the axis of the stud to supply the penetrant, but of course you then increase the risk of it shearing when you apply the torque.
Thats about all I can think of.

[Mr Gremlin]

2 ways ive done them before working at a race engineers,
let them snap and just find someone with a milling machine to drill it out and re-thread / time sert it,
or drill as big a hole down the stud as possible (preferably using a milling machine ), and get hold of some strong nitric acid and pour down the hole, it will dissolve the steel and leave the ally thread untouched.
if its that tight, it will be corroded at the bottom of the stud, unscrewing it will wind the threads out any way.

[utopia]

Hmmm. The nitric acid trick sounds interesting.
Filed away for future reference....ta.

[Mr Gremlin]

Hmmm. The nitric acid trick sounds interesting.
Filed away for future reference....ta.
tis great for removing broken taps etc too :)
i can supply (to friends etc ), but i cannot post due licensing etc.

[utopia]

Wow....that's like a backyard spark-erosion facility.
I regularly break centredrill tips, which can be a sod to get out of the work, even in ally.
Problem solved....I thank you.

[Mr Gremlin]

its only aluminium and titanium (and some stainless alloys) nitric doesnt affect , so only use to dissolve steel . another tip (if your into engineering) getting the part anodised will also remove broken taps etc including carbide mill tooling etc (obviously not the cylinder head in this post , but billed parts )

[Pedro]

Used a decent penetrating fluid like plus gas, wd40 sucks

[Dookbob]

Thanks very much for all the suggestions chaps, the one I havn,t come accross before is the nitric trick, I like that one a lot, and I might just need it because I have now sheared off the offending stud flush with the face, the other one which was corroded half way through came out ok after some more heat treatment. I know that heating the steel stud will expand it, but the technique relies on the fact that when you heat steel to cherry red it will shrink slightly smaller than its original size. Didn,t work in this case, but I have had great success on a lot of previous similar occaisions, and we used the technique on a daily basis when I worked on power plant boiler tubes. I do have a milling machine in my workshop, so its going to be a case of , head off, end mill, nitric, or spark erosion.
Utopia thinks along the same lines as I do, I did consider drilling a hole through the aluminium at 90 degrees to the stud to let the penetrating fluid get into it , that was before I had one more go and sheared it off. I have a spare engine that I have decided to install on the rebuild, so this one can go to one side untill I have time to mess some more with it. Sad thing is that one little dab of copper slip would have avoided all this, I also have three carbs with the idle mixture screws seized solid and chewed up where someone has tried to get them out and failed, copperslip would have avoided that as well. Anyway thanks again for taking an interest, I will report back when I have some good news on the stud thingy.

[Thirdway]

its only aluminium and titanium (and some stainless alloys) nitric doesnt affect , so only use to dissolve steel . another tip (if your into engineering) getting the part anodised will also remove broken taps etc including carbide mill tooling etc (obviously not the cylinder head in this post , but billed parts )

It does definitely have an effect on skin.

How strong are we talking? How long does I guess your left with iron nitrate, do you neutralise and then tip it out ? I'm fascinated by this idea, never heard anyone else talking about it.

Oh I see now, you use nitric acid in anodising to form the oxide layer. Haha I imagine someone has come in with a barrell or head, had it anodised and then asked where you put the steel bits......gone......what lost? ......nope just gone.

[Mr Gremlin]

not quite, i first used it to strip nicasil plating off barrels prior to port tuning or big boring as nicasil destroys all tooling fast. i had known of nitrics properties to dissolve steel for a while, so when a gixer head came in with 3 broken studs it gave me an opportunity to try it first hand. a diluted solution around 30% syringed carefully into the drilled stud, and replaced and repeated several times during the day proved most effective. :) and yes, be careful , it melts hands too if your not careful.

[Martin C]

Thanks very much for all the suggestions chaps, the one I havn,t come accross before is the nitric trick, I like that one a lot, and I might just need it because I have now sheared off the offending stud flush with the face, the other one which was corroded half way through came out ok after some more heat treatment. I know that heating the steel stud will expand it, but the technique relies on the fact that when you heat steel to cherry red it will shrink slightly smaller than its original size. Didn,t work in this case, but I have had great success on a lot of previous similar occaisions, and we used the technique on a daily basis when I worked on power plant boiler tubes. I do have a milling machine in my workshop, so its going to be a case of , head off, end mill, nitric, or spark erosion.
Utopia thinks along the same lines as I do, I did consider drilling a hole through the aluminium at 90 degrees to the stud to let the penetrating fluid get into it , that was before I had one more go and sheared it off. I have a spare engine that I have decided to install on the rebuild, so this one can go to one side untill I have time to mess some more with it. Sad thing is that one little dab of copper slip would have avoided all this, I also have three carbs with the idle mixture screws seized solid and chewed up where someone has tried to get them out and failed, copperslip would have avoided that as well. Anyway thanks again for taking an interest, I will report back when I have some good news on the stud thingy.

It's possible to drill-out the broken studs without removing the horizontal cylinder head. You'll need a decent, slow-speed drill and preferably cobalt-steel bits (Machine Mart). If you start with a very carefully centred small bit, and then work up through larger bits, you can generally pull out the stud's final remnants and then get away with just cleaning up the thread. If necessary, re-tap or use a thread-insert kit (MM again).