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  1. #1
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    Default cast iron repair with maganese bronze?

    need to repair theses, they are off my lathe. i know welding cast is a whole dark art to get it right so i was going to braze them, with google returning many mixed brazing rod sugestions, kind of stuck on which rod would be best or whether i best to gas braze it or tig brazing it. im after peoples experience in cast repair using the brazing method and which rods did you use and method.
    i should add these arnt particularly load bearing components. hand wheel is pretty obvious and the other 2 are the gear selectors.
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  2. #2
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    Quote Originally Posted by brendanh View Post
    need to repair theses, they are off my lathe. i know welding cast is a whole dark art to get it right so i was going to braze them, with google returning many mixed brazing rod sugestions, kind of stuck on which rod would be best or whether i best to gas braze it or tig brazing it. im after peoples experience in cast repair using the brazing method and which rods did you use and method.
    i should add these arnt particularly load bearing components. hand wheel is pretty obvious and the other 2 are the gear selectors.
    I've seen them before , they were posted on the Awesome Boilermakers Facebook page if I recall correctly. Much manure was in the air with some of the responses on that page too.
    They will repair quite nicely I would think. Many people get all worked up about repairing cast iron, but as long as you remember that cast iron does not bend, but breaks instead, you will have a fighting chance. Your handwheel will be no big drama as the offset design of the wheel will accommodate some degree of stress build up and the gear selector look to be even easier.
    I would not braze them for several reasons, but would instead use a nickel based cast iron electrode and arc weld them. Firstly, brazing will be more expensive when gas and consumables are considered, secondly any surface finishes will be totally destroyed and thirdly brazing will not accomplish anything that a nickel electrode will not in this application.
    Start by veeing out the joints enough to allow easy manipulation of the electrode, leaving a small root face to aid alignment of the components, 90° would be too much in my opinion and 60-70° would be the ticket. The reason for the minimal vee is that it minimises weld and therefore heat input. Nickel electrodes are at their best using the cold method of welding cast iron. This method entails small, short runs that are allowed to cool between runs and often peened while cooling using either an air chisel or a chipping hammer to get into the vee. I would alternate sides of the joint so it doesn't pull, front 1, back 2, front 3 +4, back 5+6 until you build up the joint thickness if you get my meaning, but cool and peen as you go. Natural air cooling will be fine. In the case of the handwheel where you have two joints to weld, use the same sequence, but weld both joints at the same time - 1+1, 2+2, 3+4+3+4, 5+6+5+6. The final peening can be done either with an air chisel or a ball pein hammer.
    In case you don't know, the peening stretches the weld metal and relieves the stress of the contracting weld. Peening is a good technique to employ on aluminium castings or even steelwork that is heavily restrained and prone to cracking. As a matter of interest, the booms on Kato cranes are peened heavily to relieve stresses built up during construction. So heavily in fact that if you went to repaint one, you would find a heavyish layer of bodyfiller on the boom to hide the hammer marks (large air hammer of course).
    Short stringer beads - no weaving, and allow to cool to warm to hot hand heat between runs and you will be fine.

  3. #3
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    Yeah it was posted there but due to lack of replys to questions i thought ild post it up here.
    The reason for brazing was to bring the cost of repair down, them nickle rods made me cry when i see the cost of them! And having access to free oxy acty just stregthened my thought for brazing.
    Thanks for your detailed responce i really havnt got any more questions now apart from got any nickle rods you want to sell cheap? I might go with the nickle rods if i can find a few of them, not too keen buying a packet of them.

  4. #4
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    I have repaired similar in the past by Oxy/brazing. Heated it up first in the oven (wife wasn't very impressed) then brazed it and placed it back in the oven for a slow cool. Worked fine.

    Geoff

  5. #5
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    Quote Originally Posted by gyropilot View Post
    I have repaired similar in the past by Oxy/brazing. Heated it up first in the oven (wife wasn't very impressed) then brazed it and placed it back in the oven for a slow cool. Worked fine.
    Quote Originally Posted by Karl Robbers View Post
    ...I would not braze them for several reasons, but would instead use a nickel based cast iron electrode and arc weld them. Firstly, brazing will be more expensive when gas and consumables are considered, secondly any surface finishes will be totally destroyed and thirdly brazing will not accomplish anything that a nickel electrode will not in this application.
    It's your call Brendan. The only suggestion I would make is to "mask off" any critical surfaces (like the bore in the handwheel) if you do decide to braze. Some people have special compounds they use and I have heard of people using borax too I think. The heat from brazing will oxidise the surface and so ruin any close fits. It may not be so critical for the gear change bits but the handwheel bore certainly. Needless to say a bit of polishing and repainting will be needed afterwards.
    That lathe really looks like it got beaten up, but if you fix it you will certainly be able to put your name to doing something with it.
    (Did you sort out the leadscrew?)

    Michael

  6. #6
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    Quote Originally Posted by brendanh View Post
    Yeah it was posted there but due to lack of replys to questions i thought ild post it up here.
    The reason for brazing was to bring the cost of repair down, them nickle rods made me cry when i see the cost of them! And having access to free oxy acty just stregthened my thought for brazing.
    Thanks for your detailed responce i really havnt got any more questions now apart from got any nickle rods you want to sell cheap? I might go with the nickle rods if i can find a few of them, not too keen buying a packet of them.
    Sadly questions asked on that page are often met with sarcasm, chest beating and turn into a piddling contest without actually answering the question.
    Yep, a 2.5 or 5Kg pack would make you cry. A company called Magma Weld sell them in handy packs which from memory contain around ten 2.5 and five 3.2mm electrodes. Actually Magma Weld offer an interesting range of electrodes in handy packs, stainless, hard facing, cast iron among others. I have seen them in Bursons Auto Parts and several welding suppliers also stock them. I think they were around the $30 dollar mark last time I bought some.
    If you don't mind heating the components and destroying surface finishes, then I would just use low hydrogen electrodes once you have preheated the whole thing. Tack it up first of course. If you go the low hydrogen route, you will have a weld deposit that can be ground, but not machined due to hardness levels. Peening will be an advantage here as well as if you braze the job, anything to reduce stresses and definitely cool slowly. Luckily your components lend themselves to expansion and contraction without too much restraint.
    If you decide to braze, try to get uncoated brazing rods and a tub of flux as it is superior to the pre coated brazing rods and allows you to really flux a stubborn job.

  7. #7
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    Ive looked on ebay and found 10 ni rods for 30bucks. 3.2mm, ive looked in my little welding handbook and a 3.2rod is good for 80-100amps which sounds aboit right for theses parts. since finding theses rods im going to be welding them, they dont need a preheat/base metal preheat do they?
    Michael, no havnt sorted the lead screw out as yet ive more been focused on getting that saddle fixed, speaking of which anyone in sydney with a medium to large mill able to do a cash job for me maching this saddle so i can make a new peive to fit back in?

  8. #8
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    Also that lead screw still go no idea on the pitch/sizing of it.

  9. #9
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    Please keep us informed, Brendan, even of failures, please!
    I've used nickel rods on several occasions, but never managed to prevent subsequent cracking next to a weld, despite peening and slow cooling. I've never had a failure brazing though.... and I'm always happy to learn!
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  10. #10
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    Quote Originally Posted by jhovel View Post
    Please keep us informed, Brendan, even of failures, please!
    I've used nickel rods on several occasions, but never managed to prevent subsequent cracking next to a weld, despite peening and slow cooling. I've never had a failure brazing though.... and I'm always happy to learn!
    A lot depends on the component. If for example you had a cast iron spoked wheel, that would be a lot more difficult than welding a lug back on a casting due to the ability of the lug to expand and contract unimpeded.
    I have found that some people are too gentle when peening, you need to stretch that metal, that's why my preference is an air chisel with the sharp edge ground back to a flat to rounded profile. Some castings can also crack at another flaw that was previously unseen.

  11. #11
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    Quote Originally Posted by brendanh View Post
    Ive looked on ebay and found 10 ni rods for 30bucks. 3.2mm, ive looked in my little welding handbook and a 3.2rod is good for 80-100amps which sounds aboit right for theses parts. since finding theses rods im going to be welding them, they dont need a preheat/base metal preheat do they?
    Michael, no havnt sorted the lead screw out as yet ive more been focused on getting that saddle fixed, speaking of which anyone in sydney with a medium to large mill able to do a cash job for me maching this saddle so i can make a new peive to fit back in?
    If you have access to a DC stick welder, then use DC current, those electrodes run much better on DC. You will also find that there will be a sweet spot amperage wise, so don't be afraid to turn them up a bit and you will need to hold a good close arc and you will find that nickel electrodes do not have a very forceful arc but just seem to hiss a bit. Often, you will put less heat in by turning your amps up and travelling quicker than trying to trickle the metal in at low amperages. If they don't seem to want to fuse in, check your cleanliness - oil contamination etc and turn your power up.
    Good luck.

  12. #12
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    Quote Originally Posted by Karl Robbers View Post
    ....
    I have found that some people are too gentle when peening, you need to stretch that metal, that's why my preference is an air chisel with the sharp edge ground back to a flat to rounded profile. Some castings can also crack at another flaw that was previously unseen.
    You may well have a good point there. I might try the air chisel method. I'm probably a bit timid hitting cast iron parts too hard - even when it's on a new weld....
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  13. #13
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    What part of Sydney are you in?

  14. #14
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    I would personaly be incline to peen ot softly for the reason i dont want to break it again! But ill keep all this in mine.

    Im in the blacktown area.

  15. #15
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    Quote Originally Posted by jhovel View Post
    You may well have a good point there. I might try the air chisel method. I'm probably a bit timid hitting cast iron parts too hard - even when it's on a new weld....
    The beauty of air chisels is that you can set them to get lots of small blows and really work the metal. Hitting it once with a 16 pound hammer will once more give you a two or more piece casting, but lots of repetitive blows whether they be from a ball pein, chipping hammer or air chisel can stretch the weld quite nicely. A lot of people stop after a couple of taps. No part of the bead should be unmarked by your peening when you finish.

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