A Wallie, Bio, posted this video as a part of a great thread that Delta T, another Wallie, started. He posted:
Thought I would share this trick for getting an old threaded fitting off, as I have not heard of this before and never seen it posted here. This works best for larger stuff 2" and up. I used it the other day on a 2 1/2" 90 and I'll be damned if it didn't work.
So, what you do is, take two mini sledge hammers (you need the large mass of a mini sledge to make this work, regular framing hammers won't do the trick) hold one tightly on the hub, and use the other one to give the fitting a good whack 180 degrees from the stationary hammer. Its more about precision and hitting exactly 180 degrees away from each other than brute force. Do this a few times, then move 30 degrees around the fitting, do it again, and so on until you have gone all the way around a couple times. It takes a little bit of feel to get it to work, you will know when you hit it just right as the stationary hammer will bounce off the fitting with more force than it seems like it should. That is what you want. If it just right, you can almost feel a resonant hum through the hammers for an instant.
Then put your wrench on and remove the fitting!
The physics as best I can work out goes like this: When you hit the fitting, you create a shock wave that sightly egg shapes the fitting for an instant. This is why the the stationary hammer pops off the other side, the shock wave, and then the fitting trying to return back to its normal circular shape cause a fairly high force to develop on the opposite side. This wave very slightly deforms the fitting in a way that breaks the bonds of corroded threads and loosens the fitting enough to get it off.
No Kroil or PB, no torch, and about 10 mins of work with the hammers, and my 2 1/2" 90 year old elbow came off with very little fuss. This after trying for 15 mins with a 3' pipe wrench and a 3' backup wrench and two people with no luck at all, called my old man to tell him this was not going to be easy and would take longer than we hoped, and he told me about this trick his old boss taught him.......still schooling me after 20 years.
No guaranties, no refunds, your results may vary, but it worked for me :)
Any one else ever try this?
Hammers are great. That's a great trick never tried that.
What I have found with unions is the worst rusted, painted union big pipe wrench with cheaters and it won't budge no matter how hard you try. Take a hammer and rap the union nut in 3-4 places around it. I have had union nuts spin off with my hands after that.
My favorite trick to get a fitting off is to slice it with a grinder with a cutting disk. Then drive an old screwdriver in the crack to wedge it apart.
That was kind of how this 90 went. I did the hammer thing, put the three-foot wrench up on it, and got ready to pull hard against the backup and it came off so easy, I probably could have used my little 14-inch wrench, if the jaws opened that wide, of course. Very easy, after the initial pull, which was hardly anything; the weight of the wrench turned it.
I like this trick because there is virtually no risk of damaging the male threads, and I have definitely had a few stressful cut-and-remove situations where if the male threads got too screwed up. We in turn got....ahem.....well.....screwed. :p
We have all had those. I have nicked some threads with the Sawzall pretty good. Teflon tape and dope usually seal them up.
Just like cracking cast iron fittings. The backup hammer is more important than the one you hit with.
Good trick will have to try that. Problem is sometimes there is no room to swing the hammer.
Bob Bona wrote:
Yup that's an old one. The precursor to step 2. Cracking the hub, if cast.
I've heard of it, but in application of cracking cast fittings off. Never had to try it in anger yet though.
At this point, Bio posted his video. To which EBEBRATT-Ed replied:
Exactly. But IMHO it works better if the backup hammer is larger than the striking hammer. Sometimes I will slice a CI fitting with a cutting disk 3/4 of the depth to stay away from the threads and then use the hammers. Breaks easily with less pounding or risking damage to fittings nearby that you want to reuse.
Had to resort to this many times. Smaller for the striking hammer as Ed said
Hot Rod wrote:
It works well on frozen nuts and bolts also, an old farmers trick.