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    Default Seasoning Cast Iron.

    How long should a grey iron casting season before it is machined. Or should it be rough machined, seasoned, then finished. We made some pillow blocks for a customer. They are about 9 inches square 2 inches thick. 6 inch hole in center. First piece inspection, using a CMM, showed a good part. GD&T were tight tolerances. After about a week, during final inspection, geometric tolerances were all over the place. The customer would not accept the parts.

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    Unusual for CI to be aged now,it is normally heat treated.

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    Quote Originally Posted by camscan View Post
    Unusual for CI to be aged now,it is normally heat treated.
    Thermal or vibration stress relief, OP should do a search. Aging is hit-or-miss, but if you don't have other options, rough to perhaps 20% of final geometry, set aside as long as you can, semi-finish to 10%, set aside, finish. No guarantees, but it's better than cutting once and having it move.

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    Old school "seasoning" cast iron isn't doing anything to help the iron, other than just giving it a long time to move around and relax. Thermal or vibration stress relief actually makes that happen in a short time, instead of leaving it to nature.

    Seasoning technically works. It's just terribly inefficient.

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    I came here for the wrong kind of information. You see, my morning eggs are starting to stick to my pan...

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    I believe that Bridgeport used to season their castings for a year out in the yard. On the other end of the spectrum Minster used to shot blast their castings in order to stress relieve them. Both methods seemed to work fine.

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    72 years ago the US Navy did a careful study on the subject. They debunked the then-long-held tradition of storing cast iron "in the weather" and under various conditions to reduce internal stresses in the cast iron piece. Here is a link:https://apps.dtic.mil/dtic/tr/fulltext/u2/620556.pdf They did show that properly done high_temperature thermal stress relief is effective.

    If you are interested in the subject, take a few minutes to read it. Old traditions die hard as you will still hear many advocating for aging castings. Vibratory stress relief has its advocates but is controversial as to whether it works and in what circumstances it might work. From Wiki which has no axe to grind in this matter "The effectiveness of vibratory stress relief is highly questionable.[4] In general, the strain amplitudes achieved during vibratory stress relief are too low to exceed the critical stress required to activate mechanical relaxation during the induced low amplitude high cycle fatigue excitation of the transducer vibrations. If the strain amplitudes were increased to a level sufficient to cause instability in the residual stresses, fatigue damage would occur.[5][6] For most applications, conventional stress relief methodologies should be applied to components that require the reduction of residual stresses.[7]"

    You will find a whole bunch of papers purporting to support vibratory stress relief on the Web. But those all trace back to the companies hustling vibratory equipment. None come from independent sources, universities etc.

    This seems to be a subject that stirs heated (so to speak) discussion and lots of anecdotes. I listen to the science on the subject.

    Denis

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    I have been highly sceptical it claims of vibration stress relief (and weathering) for the very reasons listed. There simply isn't enough energy to do anything to a casting and any changes would have taken place with or without the "treatment". Just heat treat and forget the other stuff.

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    Hang them up and whack them for several minutes with a two by four.

    At least that's what one contributor swears will work.

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    I don’t know if this is just hearsay but in the sixties I heard or read somewhere that Volvo after casting their B16 engine blocks and pre-machining them they were left outside for approx 1 year and were then rebored and linebored to the final size. Whether this is just an urban legend or true or just a bragging dealer for Volvo that started this story in South Africa
    Guv


    Sent from my iPad using Tapatalk

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    Yes, substitute “John Deere” “GM””Caterpillar” in above post. The stories abound and some may have been true at one time.

    Denis

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    Was this machined from a casting? Or from Dura-Bar? (Really doesn't manner.)

    If it was me, rough them out leaving .060-.120" on all surfaces. Throw in oven, heat to 900 deg. F, hold at temperature for at least 1 hour per inch of thickness, oven cool to ambient. Overnight typical. Doing the finish machining, ease up on fixture, /vise, chuck pressures an proceed to finish parts.

    Just my two cents worth! Ken

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    Quote Originally Posted by BoxcarPete View Post
    I came here for the wrong kind of information. You see, my morning eggs are starting to stick to my pan...
    Search...that topic has been covered here. I know Forrest had some good methods.

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    Quote Originally Posted by BoxcarPete View Post
    I came here for the wrong kind of information. You see, my morning eggs are starting to stick to my pan...
    WD40 - never fails.

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    Quote Originally Posted by Limy Sami View Post
    WD40 - never fails.
    Considering that many Haas machines use repurposed stovetop heating coils as regen dissipators, we really need a cookbook for those late-night work sessions where you just can't leave the shop. I wonder if I can make an omelet if I program a lot of start-stops?

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    I have a beautiful old precision level, at least it was a precision level, not sure what happened to it, but its got enough twist you can put an 1/8" shim under one corner. I've always assumed it was not seasoned right.

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    Quote Originally Posted by Milland View Post
    Considering that many Haas machines use repurposed stovetop heating coils as regen dissipators, we really need a cookbook for those late-night work sessions where you just can't leave the shop. I wonder if I can make an omelet if I program a lot of start-stops?
    Or pasta with Pesto sauce?

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    Quote Originally Posted by dgfoster View Post
    72 years ago the US Navy did a careful study on the subject. They debunked the then-long-held tradition of storing cast iron "in the weather" and under various conditions to reduce internal stresses in the cast iron piece. Here is a link:https://apps.dtic.mil/dtic/tr/fulltext/u2/620556.pdf They did show that properly done high_temperature thermal stress relief is effective.

    If you are interested in the subject, take a few minutes to read it. Old traditions die hard as you will still hear many advocating for aging castings. Vibratory stress relief has its advocates but is controversial as to whether it works and in what circumstances it might work. From Wiki which has no axe to grind in this matter "The effectiveness of vibratory stress relief is highly questionable.[4] In general, the strain amplitudes achieved during vibratory stress relief are too low to exceed the critical stress required to activate mechanical relaxation during the induced low amplitude high cycle fatigue excitation of the transducer vibrations. If the strain amplitudes were increased to a level sufficient to cause instability in the residual stresses, fatigue damage would occur.[5][6] For most applications, conventional stress relief methodologies should be applied to components that require the reduction of residual stresses.[7]"

    You will find a whole bunch of papers purporting to support vibratory stress relief on the Web. But those all trace back to the companies hustling vibratory equipment. None come from independent sources, universities etc.

    This seems to be a subject that stirs heated (so to speak) discussion and lots of anecdotes. I listen to the science on the subject.

    Denis


    I wonder if anyone ever reads the report? After all of these years members still think ageing will stress relive a casting.


    To the OP, Your part may be creeping a bit over time. The warpage may be introduced when you are clamping the part and machining it. The part may not be springing back immediately to its relaxed state.
    You might be able to minimize warpage by reducing clamping forces on your part during finishing. Or Rough- semi finish - finish each with a loser clamping torque. It will spring back over time, this might halv the moment.

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    Quote Originally Posted by dalmatiangirl61 View Post
    I have a beautiful old precision level, at least it was a precision level, not sure what happened to it, but its got enough twist you can put an 1/8" shim under one corner. I've always assumed it was not seasoned right.
    That's really interesting. I wouldn't expect that much no matter how much stress was left. You'd think a casting stressed like that might just blow up sitting in the back lot aging.

    Perhaps it's encountered an event in life like a previous owner using it for something else. Lots of room for creative speculation here. So a guy was doing a machine install late at night and had the level out there for when he got the machine pretty well situated. Unbeknownst to him, a mouse had been busy building a nest in the crane control box and had just stuffed a little piece of something in place that could leak current and cause the crane to creep. The guy hasn't thought to unhook the chain since it's slack enough but it's been slowly tightening up. He'd have been just fine if he hadn't propped his boot right between those two components while he stretched to reach the installation papers. Suddenly he can feel something tightening on his foot. He tries to jerk out but he's really stuck. He yells for help even though he knows he's the last guy in the shop. Damn, his cell phone is over there on the bench with his lunch bucket. Frantically looking around he spots the level right there within reach. ....

    Well, others might have a different explanation.

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    Quote Originally Posted by dalmatiangirl61 View Post
    I have a beautiful old precision level, at least it was a precision level, not sure what happened to it, but its got enough twist you can put an 1/8" shim under one corner. I've always assumed it was not seasoned right.
    WD40 - never fails.


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