Exhaust Dismantling

Hi there,
Can anyone tell me the standard bolt/nut size used for 2" diameter exhaust clamps, please? Also, any tips for dismantling the system,
seperating the pipe from the silencer boxes, unions and whatnot? I'm finding the heat-induced corrosion on the unions a bit of a problem. :(
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On 06/05/2017 01:04, Chris wrote:

The nut sizes are variable depending on car and originality and which bit of exhaust. Common sizes are 13, 15 and 17 mm, some vehicles need special spring-clamp removing pliers.
As to separation: With the right tools and experience most exhausts can be dismantled for re-use, if they are not too rotten. If you are replacing the back section of exhaust it is often best to cut the pipe just after the join, slit the remaing stub and twist it out.
If the joins are 'slide one pipe inside another', then after loosening the clamp spray liberally withe rust dissolver and leave for as long as practical, give the exhaust join a good tapping with a hammer before and during the soaking, then try and wiggle the exhaust apart, once you get the tiniest bit of movement you are on the way. Other ways to get it started involve heat from a blowtorch or induction heater or an air chisel.
Seriously stuck exhausts may even have to be cut apart and rewelded as needed. Another method that I sometimes use is to extend the join slit of the outer pipe to relieve the tightness, pull the exhaust apart and weld the slits up again, there are also various air chisel ends to take exhausts apart, plus specialised thin curved chisels which can open up the join.
The difficulty of separating exhaust components is why most exhaust places do not bother and just fit the whole lot after cutting the old off as needed.
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On Sat, 06 May 2017 07:04:16 +0100, MrCheerful wrote:
[...]
There speaks the voice of long experience, I'm guessing. Thanks for your tips, Mr. C!
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On 06/05/2017 12:16, Chris wrote:

yep, about 50 years!
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On Sat, 06 May 2017 07:04:16 +0100, MrCheerful wrote:

Could this be done with an old-style arc welder or is exhaust pipe too thin for anything other than gas or mig?
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On 06/05/2017 16:55, Al wrote:

You would really struggle with an arc welder on normal exhaust, particularly as the metal gets older, rustier and thinner. Mig, tig or oxy-acetylene would be first choices, unless you are really good with a stick welder and used to such thin stuff. I am lucky enough to have all available, but I cannot remember the last time I got the stick welder out of storage to use it (probably thirty years) and would not even try it on anything normal unless there was absolutely no alternative.
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On Sat, 06 May 2017 17:16:17 +0100, MrCheerful wrote:

I still keep an Oxford oil cooled 300 Amp job, though. For heavy plate you can't beat it. Many times over the years I've needed to knock up a jig or a hydraulic press or a vehicle stand or whatever that requires strong jointing of thick steel parts, and there's simply no comparison.
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On 06/05/2017 22:49, Cursitor Doom wrote:

For normal everyday fabrication up to half inch stuff, the Mig is fine, luckily enough I rarely need to use anything even approaching the total capacity of any of the sets I have. I did use big arc sets years ago, but have had no need since.
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On Sat, 06 May 2017 23:30:20 +0100, MrCheerful wrote:

Well that sounds very impressive. Half-inch with a mig! Bet your gear can't keep that up all day long, though! Mine can! Hehehehe!:-)
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On 07/05/2017 11:02, Cursitor Doom wrote:

Willy waving ?
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On Sun, 07 May 2017 12:44:14 +0100, MrCheerful wrote:

Just sticking up for the old gear. ;-)
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yes for one pipe inside another' i use a air chisel nibbler if its the side you need to replace
http://espimages.biz/2386/I/630/5/AK57-5.jpg
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On 5/6/2017 7:04 AM, MrCheerful wrote:

A perfect answer! Having stood underneath the ramps to confirm the competence of my local firm, I shall *never* touch another exhaust again (unless I have to rip something off on the road).
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On 06/05/2017 07:04, MrCheerful wrote:
<snip> > If the joins are 'slide one pipe inside another', then after loosening

What stuff did you have in mind?
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On 07/05/2017 13:47, Fredxxx wrote:

I have a tin made by pattex, it came from a Lidl store, but not usual stock.
Vinegar is actually a good rust remover, and everyone has some of that, and it's cheap!
WD40 would be better than nothing.
I used to get a product called Lusol which was very good, despite the dodgy name.
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On Sun, 07 May 2017 14:23:25 +0100, MrCheerful wrote:

The problem AISI is that you can't get *any* stuff, no matter how good, into the inside of an exhaust union joint where it's really needed.
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