Spark erosion

BarryH

BarryH

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Serious post for once, from me anyway. Started to do the dreaded winterizing of the boat. Can't use it anymore 'cos the wife has found a new hobby for me, decorating!! Anyhow I digress. Whilst changing the coolant in the freshwater system, I noticed that one of the thermostat housing bolts looked loose. Ha, it was, but it had seared clean off level with the cylinder head. Mild steel bolt in an ali head, not good. Why the hell do they do that! Tried all my enginnering contacts and they all want the head off, stripped of cam and valves etc. I was't gonna do this if at all poss as I done it at the begining of the season. Anyone know of anyone in the southeast that does a mobile spark eroision sevice in the south east per chance!!
 
Have you exhausted all the other methods yet, drilling stud extractoirs etc yet? I would do all that first, you may find it will come out. When drilling, have a vacunm cleaner sucking any debris and cuttings away as you drill. I would not be looking at spark erosion, until all other avenues have been used up. I would also look at drilling out, extracting and or fitting a helicoil thread insert. If the bolt didn't shear when You were trying to remove it, it may well be quite loose in the hole. Just one other thing, what other material would you suggest for the bolt in aluminium? Don't say stainless, this is not a trick question.
 
You could:

1. Drill out (and helicoil, if the thread in the alu gets a bit mashed),
2 drill a smaller hole right down the centre and tap it with a left handed tap, and screw in a left handed bolt, then it will come out.
3 Or, depending on the shape of the thermostat housing, drill and tap new hole alongside the old one, and drill a new hole in the thermostat housing, and use that (or do 2)

I thort spark erosion was used to cut metal to very fine size tolerances. Can it be used to extract a broken stud then?
 
Agree with Colin and jfm that spark errosion would be my last option. If this bolt has sheared off then there is a good chance that it is a fairly soft steel one and so it should be easy to drill out. Oh and do chect that you aren't drilling too deep, if the other bolt will come out measure it's length and put a bit of tape round the drill bit.

If space permitts I'd be tempted to replace the bolts with some studs, nuts and washers, at least you won't have that problem again.

KevL

--
It may be the early bird that catches the worm but its the second mouse that gets the cheese.
 
Be very careful with lefthanded taps (we used to call them 'easy-outs') They are made from tough but brittle material and have a tendancy to snap off thus making the problem ten times worse. Suggest when you have drilled out the middle of the stud to apply heat and release oil before attempting the 'easy-out'
best of luck
David
 
I was going to suggest heating also, however I'm not too sure about the heating of an alloy head? Could it warp? Heating always works on my Minis (A series steel head!!!)



Relaxation starts at the pontoon gate
 
Hmm, yep tried the drill and easy out option. The easy out.......well er ain't so easy to get out! Apllied the heat and all the other things mention'd, and a few besides. I thought about replacing with studs, but being a volvo, it ain't that easy as the bolt heads are recessed and there isn't that much room. I turned down a socket to enable me to get the original bolts out. May look into it again tho.

I've a mate that runs an engineering business. He's used spark erosion to remove other studs and stuff before for me. He said about the insert, if it was the other hole that would be ok, but this one is right on the edge of the head casting. I don't think there's enuff meat to machine. Still I've got the rest of the winter to play about with it. One other point, Laying up the engine for the winter, I've been told to fill the bores with oil. Used the storage seal stuff before, nasty goopy stuff that fouls plugs like hell and gums piston rings, but never heard of filling the bores with oil!!
 
'fraid not. I looked at that option aswell. Looks like it gonna be a head off strip down job. I don't want to apply too much localised heat. I think I'll be asking for trouble, ali cylider heads and all that. Learnt my lesson with ali engines years ago with a Sunbeam Stiletto that I had. Some of'em learnt the hard way!
 
I've got broken studs out of ally cylinders before by drilling a line of small holes across them, knocking the sides in with a cold chisel to make a scewdriver slot and using one of those screwdriver heads in a socket with a tommy bar to unscrew it. A bit Harry Tate but it has worked.
 
In reply to your question about what metal you would use...It doen't make much difference 'cos its the ally that corrodes and jams due to electrical differential between the two metals.

The answer is to shut the gate after the horse has bolted. In other words, when you have the problem sorted, the new bolt should be greased before re-assembly.

Lesson learned from all ally Honda motor bike engines.

Madoc Yacht Club
<A target="_blank" HREF=http://www.madocyachtclub.co.uk>http://www.madocyachtclub.co.uk</A>
 
Barry, I have succesfully removed broken studs, by putting an old scap nut centrally over stud, then MIG welding it to the stud untill you have filled the nut with weld, use high current for good penatration (sp?)
The combination of thermal shock, and having somthing to put a socket over nearly always does the trick. Good luck.

<A target="_blank" HREF=http://www.arweb.co.uk/argallery/colspics> Cols Picture Album</A>
 
That was the point I wss trying to make, use mild steel plated bolts, with a bit of copper coat, that'll do it. I was just trying to make the point, as he said like dum volvo using mild steel. Don't use stainless, twice as bad, i've also done quite a bit of work on ally engines, like V8 rovers, V12 jags, V12 meteors and quite a few others!
 
Well I thought about that, but I reckon the localised heat on the ali head would play havoc with it. Just changed the headgasket at the begining of the season. I'll try the less drastic ways first. The mig is looking like the next tool thats gonna be dragged into service tho.
 
We've done all this many times at work Barry. Afraid you seem to have tried all the obviose. Only thing left it seems is to spark it out. Never heard of a transportable sparker. Besided it's done under a fluid so you cant just lean it over or upside down. Bolts are usually to hard to drill.

<font color=blue>The X Invisible Volunteer/forums/images/icons/laugh.gif<font color=red>

Haydn
 
There is a trick that no one else seems to have mentioned. Dilute nitric acid (equal parts of concentrated acid and water) will attack steel, but passivates aluminium. We used to use it when we broke taps in aluminium. Build a small dam with Plasticine round the stud, and leave the acid to work over night. But remember that acid is dangerous; where rubber gloves and goggles.
 
I did similar trick on a Jag V12 engine a couple of years ago. Built a little dam round the broken stud with plasticene and filled it with, now you're not going to believe me, but honest, Wonder Wheels alloy wheel cleaner. This was told to me by the Tech Editor of the Jag Enthusiasts magazine. And it worked. I'd previously tried "easy outs" and broken them off, but after a couple of days soaking in Wonder Wheels, put antoher easyout in and came out sweet as a nut (excuse the little joke there).

But only use Wonder Wheels, none of the others are as good. Have heard it said you can also use Coca Cola, but not tried it. Something to do with the acid in the WW (and Coke) attacks and loosens the aly\steel joint. Dunno the technicalities of it, but it worked for me.
 
Didn't think you could use WW on bare ally. It says on the warnings not to use it on any uncoated/painted ally. Or does it give a clean break! (sorry, thort I'd get one in). I've tried the coke thing, don't work with todays coke, used to work with coke of yesteryear! Showing my age now! Looks like its gonna be the head off thing. Oh well I'll get me spanners and torque wrench.
 
I can only tell you what I was told by the Tech man on the Jag Enthusiasts magazine. Mark someone, or might have been someone Marks. Anyway supposed to be the top Jag engine man in the UK. But then aren't they all? Bit like doctors, everyone's always got "the top specialist in the country" for their illness.

Dunno anything about possible reaction with WW and bare ally, but it worked on the V12 so your piddly little v**vo should be a doddle. (He says ducking).

This all came about 'cos i'd been trying to get one of the heads off the Jag and it was stuck solid. All the nuts were off, most of the studs were out, one of 'em sheared off (flush with the block as I found out MUCH later) but still the bugger wouldn't shift. Stuck solid on one or two studs. Tried turning it over. Nope. Put a chain hoist on the head up to my garage roof, angled to give a correct pull, tightened till the wheels of the whole car were off the ground (nice sag in the roof still there today). Nope. Sprayed more cans of Plus Gas and WD40 than you can imagine on it. Left it hanging for several days. Still no movement. Took engine and gearbox out of the car, tried "gentle" tapping. With a four pound club hammer. Bastard just sat there grinning at me. Spoke to several Jag dealers and specialists and they couldn't think of anything else. Apart from everyone said I'd left a bolt in. But I hadn't. Tried blowlamp. Then phoned the Tech Specialist in the Jag Mag and he said only two things left to try.

The Wonder Wheels trick or Hacksaw\oxyacetyne the head off. A bit of a toss up which to try first, so decided on the WW one first. After a day it moved. A millimetre. Then loads more WW everywhere and eventually off it came. When the head was off found the "sheared flush" bolt, so tried an Easyout and broke it. Then tried the WW trick again and after leaving it to soak for another day, screwed in another Easyout (didn't know they were called that BTW, I've always called 'em broken stud removers, good name though - Easyout) and out it came.

So that's my story. Not tried Coke just heard about, but apparantly it has to be classic Coke, none of this modern Diet muck.

So there you are. That's my two pennorth and of course this advice is worth exactly what you've paid for it.

<P ID="edit"><FONT SIZE=-1>Edited by coliholic on 30/10/2002 22:23 (server time).</FONT></P>
 
Got to be worth a can of Soltron to Colin for that one and heres me with a box full!! Colin. Darling. Remember asking Nigh pleading, for a shirt. Well it's bloody here. Waiting patiently. On top of the freezer! But no address forthcoming and cheque! Well we live in hope/forums/images/icons/laugh.gif

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<font color=red> Haydn
 
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