There's a thread on bushing removal but I can't find it. I need to remove some excavator stick end bushings. I think they're nickle bronze but don't really know. They don't weld worth a darn, can't weld the inside to get them out. Gramps had a trick but I can't remember it. Any advice appreciated. Rob
Ray's info. in post #6 may be your answer if you can't run weld beads in it.
If Gramps has a trick it prolly involves freezing them out.
The trick..... http://i864.photobucket.com/albums/ab208/parkrapids/1203121601a.jpg The trick you were thinking about Rob is the pilot bushing deal,,,, taking a shaft the same size as the pilot ID.... stuffing soaked in water newspaper in the hole , driving the shaft in and the pilot bearing pops out..... Lmao.. your as forgetfull as I am... How old are you again? bwah haha ef ef
Now THAT'S cold! Bah ha ha ha hahahaha :lmao I know what type of bushing your taking about Rob, it's like they have a bronze coating on the bushing, don't weld worth crap, but they will melt. I melt a groove in them with a torch like was suggested in that thread link. Melt a groove along the top of the bushing letting the slag drop to the bottom. Works pretty good for me since welding don't work.
Thanks for the help guys. I'll be darned but they came out with a drift and a sledge. First time ever. I'll cut the old ones with a torch to practice doing it. I think those Hitachi bushings a 'c' hair bigger than the bore.
If the digger is an Hitachi it will have a lot more interference on the bearing than say a Cat or Komatsu. Some of the bigger Hitachi diggers with say 10 or 12 inch bearings will have 20 thou crush on them which means bores last a lot longer than most other machines. If your bearing is around 4 inch it could still have around 9 thou crush and thats very tight in a 4 inch bore. As others have said a couple of melt lines through a steel or bronze bush and it will come out easy when cool. A melt line through a bronze bearing followed by a hose and you will have it fall out onto your foot Its a very easy thing to do and far better than cutting with a torch or the worst of all an arc air torch. I have seen so many bores with cracks in them because of hard spots caused by a carbon touching. In a alloy steel bore its a disaster for the owner. Not for me
What's a "melt line"? Bushings are in a 120- 65mm pin.
Ray, If you were installing bushings in the boom/arm/bucket of a Hitachi 3600 would you both heat the structure and chill the bush with liquid nitrogen, or is the nitrogen on its own sufficient to get enough shrink on the bushes to allow them to be fitted by simply pushing by hand ..? We're being told to do the heat + freezing thing and I'm not sure myself that it's necessary, although TBH it's the first time I've worked with a big Hitachi.
Rob,get a good sized rosebud torch or a big cutting tip and starting at the edge of the bearing hold the flame close and heat till the surface of the bearing starts to melt. Slowly move the torch through melting as you go. If its a good sized bore in an Hitachi you may have to do another opposite (in a steel bearing) bronze will shrink dramatically
Nige,a 3600 will normally have 0.34mm to 0.5 crush on the bearings.( 14 - 20 thou ) A handy rule of thumb for steel bearings in Nitrogen is that that they will shrink 2 thou per inch of diameter. So 3600 bearings will come down around 20 thou. They will start expanding the moment you get them out of the liquid. With Hitachi's I would normally heat the bore to 150 C minimum. Use a big soft flame and be careful to heat the hole evenly. No heating inside the bore! A infra red temp gun is the go and remember they will give a dud reading on a machined surface. Another rule of thumb is a 12 inch bore will expand 1 thou per 10 deg C, A 6 inch bore half a thou etc. To start a 10 inch bearing in a bore and you have limited time you need a fair amount of clearance. Now those other diggers, Liebherrs (which without line borers would be broke) only run a max of 4 thou crush.And if you bore them up on the top of their tolerance can be only 2 thou, you don't need any heat when using nitrogen. You can toss the bearing in from 20 feet. With bronze bearings rule of thumb for shrinking in nitrogen is 4 thou per inch of diameter. You will never need heat to put them in. The first time I did a RH200 stick I panicked. I had bored around a 300mm bore and shrunk the bronze bearing and it went in with so much clearance I was sure I had machined the hole a mm to big. Had to pull it out and check.It was correct so put the bearing back in and it was 5 or so minutes before it got tight.
So Ray, you're not doing any cutting making the melt line? The guy that used to build our buckets told me to heat the bore to get bushings in. I used to use the nitrogen but it doesn't work as well with the Hitachi bushings. I heat the bores them with a rosebud for about a minute and they go in without to much struggle. It's also easier to get them started. But why do you say not to heat the inside of the bore?
RayF you said something before about a dud reading with heat gun on machined surface hadnt heard that before , whats the deal???:beatsme
No Rob,no cutting. What happens is that the heat you apply makes the bearing expand but the bore is holding it from doing so. Because the bearing is red hot along the heat line the metal will compress in on itself in that area.So as it cools and shrinks it will become loose in the bore. Because if the inside of the bore is a lot hotter than the outside the metal there is trying to expand more than the outside. It has to go somewhere and the only place for it to go is in. You can actually make the bore smaller by heating the inside hotter than the outside. What you are aiming for is a consistent heat over the whole boss.
I don't know how or why its so. I don't really know how they work. But its easily checked. Just point the gun at the newly machined surface of a hot bore and then on a dull or painted surface right next to it. You will get a big difference in the reading. The machined/shiny surface will read maybe half.
IR thermometers work on emitted energy. A machined surface is highly reflective which scatters the energy and gives lower readings. If you paint the surface flat black or place a piece of tape on it you could measure it accurately.
Ray excellent post. I never thought about it that way. It just makes a ton of sense!!
Thanks OldandWorn,even a line borer can understand that And glad you can understand that Oarwhat. If you can have a fool around with a torch and a micrometer you find out all sorts of stuff
The brightest stars are always the most modest.
I know that you can air arc a bronze bushing out, I just watched one of our mechanics do that with the upper bearing on a 16M articulation hitch that I just bored this last week.. It splatters bronze everywhere but it will come out. The bad part about air arcs is that being a little too careless can cause alot of work for the bore man. I like RayF's way, it has worked the best for me.
Thanks for the answer Ray. Funny, I found some slag under that sleeve they use in the bore between the bushings. Looked it up and the company bought the machine when it was 5 years old. I assume it was left over from line boring but 5 years seems to be kinda fast for wearing it out. It's also 12 years old and the pins and bushing were worn but only about 1/2 way.
It depends on how the machine was cared for. The pipeline crews can run through a set of stick bearings in a year or two.