Using O/A torch to loosen corroded parts

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I'm still pretty new (15 months) to welding and usage of an O/A kit.  But I seem to remember hearing you can use the heat the torch provides to loosen corroded parts- for example, nuts corroded onto bolts, or steel sleeves that should slide on guide-rods, and things of this sort.I'm assuming that the best approach is to heat the outer part (sleeve, nut, or whatever) to red heat, so that the heat will expand that part (and possiby destroy some of the rust?).  Is this correct?I'm pretty sure you'd just want to use the outer flame ("flame envelope), not the extremely hot inner flame... wouldn't  want to met anything.  Just wondering if people here have had success with this method of using an O/A torch in situations where the corrosion is too great for penetrating oil to do the job.
Reply:I don't know about corroded parts.  but I have used a torch (O/A and just propane/mapp) to loosen tight fitting parts like bearing races, front end parts and such.  If the part are corroded that bad, one whack with a 3lb sledge might do the trick!  Be careful when using oil with heat.
Reply:Yes, you can use a torch to get corroded parts apart. Around here, nothing would come apart without a torch. It is amazing what a little heat will do.Miller millermatic 251Miller aircrafter 330st, wp201961 Lincoln SA200Ellis 1600 bandsawLogan 820 latheSouth Bend 13"Bridgeport M Head
Reply:Originally Posted by imc188222Yes, you can use a torch to get corroded parts apart. Around here, nothing would come apart without a torch. It is amazing what a little heat will do.
Reply:The idea is to get the outer part to expand faster than the inner part by heating it and so break the bond. You need to heat it fast because if you heat it slow usually both pieces heat together. Sometimes this will work also, but it usually works better if they heat at separate rates. You can also cool the part after heating and get it to shrink suddenly and sometimes break the bond with the shock that way.If you are good with a torch and its set right, you can also just burn the parts away. I can usually cut the nuts off bolts without damaging the threads if I am very careful and my buddy can burn large bolts out of threaded holes without destroying the threads.As far as the iron vise, maybe but I doubt it. I would have tried soaking it in penetrating oil, IE drop it in a bucket of the stuff. I've had luck with freeing stuck parts by putting them in the big ultrasonic cleaner with oil at work, or by electrolysis. I believe Swells covered the electrolysis in a thread a while back.
Reply:I am a mechanic and I use a torch A LOT.  I heat the manifold and stud till they are red and spin the stud out with a socket.  What ever size I have to almost drive on the nut.  I haven't broken a manifold bolt in years. You NEED the right size tip for the right job.The "Blue tip Wrench"David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by JC'sWelding If the part are corroded that bad, one whack with a 3lb sledge might do the trick!  Be careful when using oil with heat.
Reply:No, maybe I said it wrong.  If it's just a corroded rusty part, I sometimes put the wrench on, then use a dead blow hammer to "nudge" it.  But, that's when it is just covered in red, flaky rust, and I have squirted some PBR in it and let it sit.  But this is when I KNOW I am going to replace parts/bolts.  If it's a wheel bearing, steering knuckle, something like that that was pressed in, then yes, I use a torch to heat it first.
Reply:Torch works great.Most of the time all you have to do is heat a small part of the radius on an nut, or bearing race.When pulling a stubborn race, or other part that has to be pulled, I usually use a 2 or 3 leg puller, apply force, then heat a small part of the race red hot almost to the melting point.  Sometimes you can actually hear the metal pop as the force of the puller moves it.  You don't have to crank down on the puller until you almost spring it, just enough force to make sure it's really tight.  The heat and expansion do the rest.  Sometimes it takes a few cycles to get the part off.You would be amazed what a 5-10ton hand wrench type puller can do with heat.  You don't always need a 50 ton press if the part can be heated.Greasy front end parts are sometimes a little bit of fun.  It's really a bummer to watch the entire engine compartment start on fire from the grease ya just lit  Clean the area, and have an extinguisher handy.  A GOOD EXTINGUISHER, A 16OZ ORANGE CRUSH DOESN'T QUALIFY"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Bearing races on a shaft I heat one spot till its glowing and peen it with a 24 oz hammer (The rounded end)   It stretches that spot now its bigger.For races in a housing like a rotor, I weld a bead around the bearing.  It shrinks it.This also heats the hub to make it more receptive to the new bearing I have in the freezer.Both will fall off when cool.David Last edited by David R; 06-10-2009 at 06:51 PM.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by farmersammGreasy front end parts are sometimes a little bit of fun.  It's really a bummer to watch the entire engine compartment start on fire from the grease ya just lit  Clean the area, and have an extinguisher handy.  A GOOD EXTINGUISHER, A 16OZ ORANGE CRUSH DOESN'T QUALIFY
Reply:Originally Posted by Craig in Denver
Reply:Originally Posted by farmersammGiggle all ya want, but I learned the HARD WAY  Giggles appreciated(It's the heavy black smoke that really sucks, lets everyone in the vicinity know that you're a dummy)
Reply:Originally Posted by Joel_BCThanks. Okay, well I'm wondering about technique.  Did I describe what amounts to the best way to generally go about it?  In other words, heat (say) the nut or the sleeve - the outer part?Also, what about with cast iron?  For instance, I had a woodworking vice that someone gave me and it was frozen: the screw would not move the outer jaw, because the cast iron outer jaw was frozen to the guide rods.  Could I have heated the cast part and loosened things up successfully?  (I didn't have my oxy rig when I was given the vice, so I didn't try it... but now I'm curious if the O/A could have solved the problem.)
Reply:To explain the heat thing.   I was shown in school.The instructor had a ring  on the end of a stick.  It looked like an O with a 1" hole in it. He also had a ball on a stick.  The ball would not fit through the ring.He heated the ring with a Bunsen burner and the ball went right through.The "Hole" gets bigger than the object in it.  The nut gets bigger than the bolt when both are red.Delta L over L is the forumla, but it doesn't matter.The other thing is when I weld a nut to a broken bolt to get it out.The bolt gets hot from welding the nut.  It wants to  expand in all directions because its hot.  It can only expand in length because the housing its in won't let it expand in diameter.When it cools, it shrinks In ALL directions.  SO it shrinks in diameter and becomes smaller than it was in the same hole.Make ANY sense at all?David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:I agree that the heat helps, but heating some parts also makes the metal weaker after such as a A frame of a truck where the lower ball joint is located; it cause premature wear to the part because of this. So use the best method for the job
Reply:Originally Posted by franklarabieI agree that the heat helps, but heating some parts also makes the metal weaker after such as a A frame of a truck where the lower ball joint is located; it cause premature wear to the part because of this. So use the best method for the job
Reply:Originally Posted by imc188222As far as paying attention to which part is being expanded by the heat I have not found that to matter unless you are getting into big parts like say an old brass clean out plug in a cast iron sewer pipe. For automotive stuff just heat the bolt red hot and take it out. Keep in mind that the head will twist off very easily when it is red hot. Basically, heat whatever part of the equation is feasible. Get one part of it hot enough and the rust will "degrade" and it will come apart.I am not as good at writing things up as alot of the guys on here but I hope this helped.