Kubota 8 tonne dipper bush replacement

[Muz]

Hey guys .. time for one of my Kubota KX 080 diggers to get some TLC. She been a good machine, got about 5000 hours on her from new , been a mix of op and self drive work. I give her the easy shifts ofcourse but she still earns the cash. They say every days a skool day .. when I specced the gear for this job I went to my local machine shop first for some hard bar to make the pins. They quoted me for some hard En spec, and for a 340x60 pin wanted £80 or so just for the cut bar ... bit dear but not unreasonable I thought given the quality of metal it needed to be... phoned my boys at www.molsonyoung.co.uk my dealers for 30 years or so and they said they could do a genuine Kubota pin for £40 beer vouchers .. thats a hardened, capped , machined pin sorted .. 4 ordered .....good job Ordered the bushes from www.southernplantspares.com/

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I wasnt prepared to spend the £90 per bush from Kubota when Southern only wanted £25 for a case hardened bush for the same machine. Well .. it was only when I started to burn out the old bushes I realised why they cost £90

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First you need to remove the knackered dust seal with the removal tool .. its the kinda tool lies in yer box for years and wonder why you got it.. but here it is in its natural environment.. and here is where the learning kicks in about the bushes in the machine

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That there took me 20 minutes with my oxy acetylene torch at full heat .. if it was hardened steel, like every other bush Ive burned, I would have made that cut in 20 seconds

TBC

[Muz]

I dont know what alloy the bushes were made of, but had a yellow appearance on heavily worn areas, so I'm guessing some bronze / manganese type or chrome, the burner gave off reds and greens periodically if thats any clue, but feck me, the nozzle of the burner couldn't get the metal hot enough to melt it hardly .......... oxy propane burns around 2200 deg C, oxy acetylene is much hotter at 3500 deg C and it struggled Only concentrated heat right on the tips of the blue flame from the main nozzle would do it after prolonged heat, if you opened the oxygen cutting stream, it cooled the melt pool fast, so you had to get the bush really hot and just blip the cutting stream to blow the melt pool away, it would not cut.

Another trick I learned was, on a bush thats worn, to cut it out with a torch, I always normally go for the thickest part, so I wouldnt damage the boss it was sat it, no so here .. the boss is big enough, and the bush was hard enough that you had to go for the thinnest part of the bush, and start your burn there...

One thing I did notice, was that once you had burned them, they were far easier to knock out than a conventional steel one by a huge margin they didnt bond to the boss the same at all.

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So that means turning the bucket link upside down to make it easier to get the narrowest part of the bush
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Another top tip........ dont muck about when it comes to knocking in your new bushes ... use the fact that the boss you've just worked with will be hot and slightly expanded so will be easier to batter in the new bush, but first check for any burrs round the edge of the boss, as it will likely have worn a small lip around the edge. I use a small die grinder for that

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Then its a case of re fitting with new pins, using shims to take out any other lateral slack

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Jobs a good 'un

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[Wazza]

Good pictures Muz thanks for posting them ,I have to do a bit of that on my machine soon .
Just wondering if you have tried a plasma cutter to cut the groves ,but I guess it would only work on the larger bushes that allow access for the cutting torch .

[245dlc]

It's a lot nicer when you can do the work yourself. My boss finally tightened up the Hitachi ZX160LC I've been running the last few years I had been bugging him for quite a while it was getting too loose and the clientele was certainly noticing. So finally to make a long story short he took it in to the dealer and had them do it and spent around $12-13,000CAD. I had been bugging him that we should save some costs and do it ourselves. Oh well it actually be nice to run when I get in it on Friday....

[v8druid]

Good pictures Muz thanks for posting them ,I have to do a bit of that on my machine soon .
Just wondering if you have tried a plasma cutter to cut the groves ,but I guess it would only work on the larger bushes that allow access for the cutting torch .

Plasma will almost certainly blow the boss as well ... it's not so bothered by an air gap like the oxy is

[v8druid]

It's a lot nicer when you can do the work yourself. My boss finally tightened up the Hitachi ZX160LC I've been running the last few years I had been bugging him for quite a while it was getting too loose and the clientele was certainly noticing. So finally to make a long story short he took it in to the dealer and had them do it and spent around $12-13,000CAD. I had been bugging him that we should save some costs and do it ourselves. Oh well it actually be nice to run when I get in it on Friday....

Bloody hell Bert ..... wha's he having done to it

[v8druid]

I dont know what alloy the bushes were made of, but had a yellow appearance on heavily worn areas, so I'm guessing some bronze / manganese type or chrome, the burner gave off reds and greens periodically if thats any clue, but feck me, the nozzle of the burner couldn't get the metal hot enough to melt it hardly .......... oxy propane burns around 2200 deg C, oxy acetylene is much hotter at 3500 deg C and it struggled Only concentrated heat right on the tips of the blue flame from the main nozzle would do it after prolonged heat, if you opened the oxygen cutting stream, it cooled the melt pool fast, so you had to get the bush really hot and just blip the cutting stream to blow the melt pool away, it would not cut.

Another trick I learned was, on a bush thats worn, to cut it out with a torch, I always normally go for the thickest part, so I wouldnt damage the boss it was sat it, no so here .. the boss is big enough, and the bush was hard enough that you had to go for the thinnest part of the bush, and start your burn there...

One thing I did notice, was that once you had burned them, they were far easier to knock out than a conventional steel one by a huge margin they didnt bond to the boss the same at all.

sounds like there's bronze in there somewhere Muz, poss silicon bronze

[v8druid]

.. when I specced the gear for this job I went to my local machine shop first for some hard bar to make the pins. They quoted me for some hard En spec, and for a 340x60 pin wanted £80 or so just for the cut bar ... bit dear but not unreasonable I thought given the quality of metal it needed to be...

Robbin' b'stards ..... a 3m random bar of EN10 x 70mm is about 80 quid plus the Vodka & Tonic

[245dlc]

Bloody hell Bert ..... wha's he having done to it

He used shitty grease for a long time and that brush cutter isn't very kind to it. This past year we've been using something called 'Arctic Grease' from Boss Lubricants the Snake Oil Salesman claimed you can use it in the summer too. I have serious doubts and I guess my doubts were founded. Also digging in the frost isn't kind to a machine in any way. It's getting pretty frustrating working where I am and I'm thinking about a serious change this year stay tuned.

[Wazza]

Plasma will almost certainly blow the boss as well ... it's not so bothered by an air gap like the oxy is

You could well be right and having never tried it I cant comment ,supposed to be able to gouge with em though .

[Muz]

Robbin' b'stards ..... a 3m random bar of EN10 x 70mm is about 80 quid plus the Vodka & Tonic

Thats what I thought ?

[Muz]

sounds like there's bronze in there somewhere Muz, poss silicon bronze

Thought if anyone would know you would How come it wont cut ?

[v8druid]

Thought if anyone would know you would How come it wont cut ?

you can get it to melt ..... but not burn like oxygenated steel will ... quick blips of the blow out will bubble out the melt, but then have to remelt the pool after cooling it by bubbling it out ....
if you don't 'bubble it' out it'll simply reset where it is

[v8druid]

He used shitty grease for a long time and that brush cutter isn't very kind to it. This past year we've been using something called 'Arctic Grease' from Boss Lubricants the Snake Oil Salesman claimed you can use it in the summer too. I have serious doubts and I guess my doubts were founded. Also digging in the frost isn't kind to a machine in any way. It's getting pretty frustrating working where I am and I'm thinking about a serious change this year stay tuned.

serious error of judgement on the grease front then Bert

[Muz]

you can get it to melt ..... but not burn like oxygenated steel will ... quick blips of the blow out will bubble out the melt, but then have to remelt the pool after cooling it by bubbling it out ....
if you don't 'bubble it' out it'll simply reset where it is

Yes I did all that we are on the druid outer curve here then thats ok boyo ..we need a matalurgical chemist to give the answer (was my fave subject at skool) but Im still thick