I screwed up real bad


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Thread: I screwed up real bad

  1. #1
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    Default I screwed up real bad

    I was moving a 6000lbs cylindrical grinder, by myself of corse, I managed to drop it off the rigging, only fell 2". Unfortunately that shocked the table cross slide enough to rip 2 teeth off the gear rack. The damaged part is made of cast iron, a new one costs 5k.

    I'm looking for advise on how to build up the material in the damaged area so I can remachine the missing teeth. I'm a machinist but have some welding experience too, never with cast iron.

    Help please

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  2. #2
    Member Jim Dawson's Avatar
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    Default Re: I screwed up real bad

    I have seen pictures of repaired gear teeth by drilling & tapping a row of cap screws, maybe 10-24 or 8-32 in this case. 2 or 3 across depending on how wide the rack is. Then fill in the space with nickel-bronze rod. Then machine as needed.

    Never actually done this myself.



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    Member handlewanker's Avatar
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    Default Re: I screwed up real bad

    Hi, I've done the same type of repair some years back on a lathe gear wheel....it does work if you know your stuff and apply logic to the repair method......skill with tools helps a lot.

    Don't even contemplate welding the rack up as it's an iffy situation at best with cast iron.

    Just for the record......I've welded cast iron with mild steel using a Multiplaz 3500 plasma welder.......IT WON'T WORK WITH A STICK WELDER.

    The plasma welder is like a tig welder on steroids with Oxy acetylene characteristics but with an 8,000 deg C heat source.

    This would be an almost heretical idea to any welder, but if you consider that cast iron mixed with mild steel forms an alloy with a lower carbon content than the cast iron but more than mild steel so the combination is quite successful.......you do have to preheat the weld area or thermal cracking will occur.

    BTW.....that plasma welder costs about $2400 so it's not for odd jobs......I have one and have used it for almost 5 years now and is my only go to welding source.
    Ian.



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    Monkeywrench Technician DareBee's Avatar
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    Default Re: I screwed up real bad

    We have repaired by milling out a pocket, then machining a matching insert off of a new piece of rack then screwing in place

    www.integratedmechanical.ca


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    Default Re: I screwed up real bad

    Cast iron is notoriously difficult to weld. It's possible to get reasonable results with a lot of preheating, nickel rods, and luck. But if it was me, I'd get a new rack. It sounds like the manufacturer is trying to rip you off, if they're really demanding $5k (that or the Looney's fallen further than I thought). Ask these guys what it would cost: Moore Gear Website

    Andrew Werby
    https://computersculpture.com/


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    Default Re: I screwed up real bad

    can you cut the rack where its broken and shorten it by that amount, you'll need to drill new mounting holes. it is most likely slightly longer than it needs to be.



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    Member handlewanker's Avatar
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    Default Re: I screwed up real bad

    Now that's a very good idea.....you'd end up with a good rack without the worry of a welded or repaired section breaking loose at any time and jamming the works up...... I think I would go down this path as a no. 1 choice.

    Some lathes have the rack in sections, so yes, it's feasible.......just ensure the pitch is accurate across the two halves when they're butted together.
    Ian.



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    Default Re: I screwed up real bad

    Thank you all, some very good ideas. I will post pictures of repair when done.

    Appreciate the help,
    Keith



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    Default Re: I screwed up real bad

    better yet, cut the rack out and splice in a section cut from the end. no re-drilling of mounting holes.



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I screwed up real bad

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