Removing a nut

Dear All,
Yes it's me again seeking your advice on things mechanical!
Went to remove the nuts on the big end this evening on my JAP2a so that I
could free the con rod and remove the piston to replace the rings. Got one nut off very easily but the 2nd one is proving a pig. I did use the correct Whitworth spanner but it slipped and has damaged the nut. I can't budge the thing - any advice please?
Incidentally the crown of the piston is stamped with +030",. Do I assume this means it is oversize by this amount? Regards, Ian. PS: Flywheel now removed, valve cotter pins found and removed (realised I could have done this without removing the flywheel etc as there is an access plate!), valves extracted ready for a re-grind, de-coked the piston.
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kingsnavy wrote:

Kingsnavy, Find a socket close to the size of the nut and carefully hammer into position, then undo socket. Yes +30 usually means oversize of original bore.
Martin P
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Hex socket or box spanner will get a better purchase on damaged nuts. Surface drive ring spanners are also very good if you can get one the right size.
--
NHH

"Campingstoveman" < snipped-for-privacy@btopenworld.com> wrote in message
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If you have well and truly bu**erd the hexagon, you might do worse than look at a socket from - say - a metric set. Find one that will just offer up and drive it on with a copper faced hammer at best or by using a copper/aluminium drift and a big hammer. Hitting it one or two hard blows it far better than a series of nervous taps.
As my old metalwork teacher used to say "For God's sake, boy, HIT the ****ing thing"!
Regards,
Kim Siddorn
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I once had a similar experiance with a Hillman Imp engine. All the big end bolts came out ok except one which would not budge for love nor money. Wanting to get the crank away for regrinding and expecting to have to scrap the con rod anyway, I decided to drill the bolt head off. That accomplished, the remains of the bolt proved to be hardly more than finger tight in the rod - never did understand that one!
--
NHH



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It's off !!!! :-)
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Congrats, what did the trick?
--
NHH



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Nick, The reason it went loose after you drilled the head off is because most big end bolts are one use only and after you have torqued them up they are designed to "stretch" so when you drilled the head off the stress relief on the thread lets it go loose.
Martin P

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Quite so Martin, the puzzle is why this one bolt was so b*****d tight when all the others came out with just the usual number of white knuckles. The engine still had factory fresh tab washers, rather than the usual mangled examples or loctite one usually finds, so I fully expected to find the threads locked up by a lump of Linwood swarf or something.
BTW. Not sure if Imp BE bolts are officially 'use once' but I have certainly re-used them on many occasions and never had an engine blow up (well not from BE bolt failure anyway!)
--
NHH

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Nick, If you read the history of Rootes at Linwood I am surprised they managed to build any Imps, what with the usual strife it was also unskilled labour so doing a bolt up tighter than others is not a surprise.
Martin P

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When I was a bike mechanic in the seventies, I had a guaranteed method of getting mangled case screws undone. They were invariably dead tight and frequently undisturbed from the day they left the factory. Being reliable devices, they might be in place and temperature cycling every day for years.
Anyway, I would take a flat faced drift and place it on the face of the screw, striking it one hard blow with a heavy hammer. This reformed the mangled head of the cross headed screw and loosened the thread all in one go. I had a tool kit screwdriver onto which I'd brazed a tee bar, which I could tap into the screw , getting a good grip as it made its own shaped hole. They were always finger tight by this time although very occasionally the odd one might need another thump with a drift. I must have saved days of work over the years - and don't mutter "butcher" under your breath, it preserves both case, cover AND screw from damage!
What happens inside the thread is that the upper face of the male thread and the lower face of the female are in close proximity and under great pressure. I was told at the time that the high zinc content die cast ali castings and the electrolytically zinc plated steel screws produced a perfect path for molecular flow from the iron in the screws to the aluminium in the castings, but that's all a bit scientific fur the likes of I. ;o)) Driving the screw into the thread simply shocks the two faces apart and slightly recesses the shoulder of the screw into its hole at the same time.
Regards,
Kim Siddorn
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"J K Siddorn" wrote (snip)

Hmm. I'm beginning to wonder about you, your flywheel removing scheme involved whacking it with a battle hammer as well ;-)
--
NHH



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Workshop Manual says " use special tool No ****" Translation " hit with hammer"
John
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I was told at the time that the high zinc content die cast ali

aluminium
Aluminium and steel and a touch of water is called a battery, this then causes corrosion which causes stuck screws. You can now buy for unstressed areas on bikes, cars etc aluminium bolt kits to stop the corrosion.
Martin P
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Some bolt are designed to be torqued up dry, if you use oil then they torque up much tighter due to reduced friction.
Lionel
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Did what I was told, used the next size socket down and hit it!
Thanks, Ian.

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and get the nut as hot as possible when removing it-they usually come off more easily ive found
carl ray

correct
the
access
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