gray or ductile iron for machine base?
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  1. #1
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    Default gray or ductile iron for machine base?

    I've been tasked with making a shorter base for our climax portable mill. Climax doesn't have any in stock, but will sell us a used machine for $12k that has the short base. "Gee, Kerry, that looks pretty simple.Can't you just make one?"
    Sooo.....
    I found a place that sells cast iron :
    Rectangles / Squares Ductile

    But what would be the best fit for my application?
    Thanks
    i_r_machinist

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    Ductile iron will absorb vibration better. If you hollow out the legs and fill them with sand it will absorb even more vibration.

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    Make a wood mock-up and try it on a few repeat projects before you commit to a design.

    Otherwise use DuraBar's G2. Strong, stable, easily machined, scrapes beautifully.

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    I think gray iron is nicer if you plan on hand scraping it. But ductile is better in case you drop it. You did say portable, so I anticipate it could get dropped.

    Larry

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    I don't believe DI has better dampening effect over CI.

    Ken

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    Quote Originally Posted by jscpm View Post
    Ductile iron will absorb vibration better..
    I think that is the other way around. Grey cast iron has superior damping over ductile cast iron - used ductile when you want strength and grey when you want damping

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    Quote Originally Posted by 4GSR View Post
    I don't believe DI has better dampening effect over CI.

    Ken
    You are right hit ductile with a hammer it it has a slight ring to it, hit gray cast and it just makes a thud noise.

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    ASTM A536 or 65-45-12 ductile.
    JR

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    I agree with Forrest on a prototype.

    Maybe an aluminum proto, and then if anyone has some changes or other input, you can do that to the final product.

    Also, that Dura-bar that Forrest is talking about is sweet


    JAckal

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    Is it really saving money over buying the used machine? I would give that decision a hard look to be sure all the costs of building or covered. Most times making something is much cheaper than making new if used is available. Head scratching over cast iron costs money if you are doing it on the job. What is the cost of down time building equipment compared to doing whatever brings in money rather than spending it?

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    Quote Originally Posted by Close Work View Post
    Is it really saving money over buying the used machine? I would give that decision a hard look to be sure all the costs of building or covered. Most times making something is much cheaper than making new if used is available. Head scratching over cast iron costs money if you are doing it on the job. What is the cost of down time building equipment compared to doing whatever brings in money rather than spending it?
    I agree, and have argued the point many times, but this isn't a production shop. I work in a maintenance shop at a nuke plant. My time is considered to be free and non billable. I'm treated like the fat girl in a bar. When the lights are about to go off, I'm the only show in town. After the problem is fixed, nobody knows me.
    I'm going with ductile on this one. Impact resistance is something to consider.
    Thanks to all
    have fun
    i_r_

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    I made one for the company I use to work for out of an old pcs. of A36 and it worked great for several years. I think any form of cast iron will work well for a portable aplication as the set-up are only ever temporary and the machines are seldome used for very long.

    Greg

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    good choice on the ductile as JR reccomended. I've considered making a longer track for my Versamil and searched a little bit. (Plus I have castings made and have considered the trade -offs for some other applications) Ductile does not scrape nearly as nicely as grey CI, and it is a little tougher to machine. But it has 50% - 80% better stiffness (lighter part for same section) and strenght. It also does not creep yield quite like CI does. Pearlitic ductile is eve stranger than A36/mild steel. Since the sliding components are most likely CI with adequate bearing quality, I'd choose the extra strength and hardness of Ductile if the price difference is not great.

    Simplified, but you can google for more:

    http://www.ductile.org/didata/Sectio...es/pfig3_3.htm

    smt

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    Grey iron is the choice for damping. Engine blocks and heads are (were?) made from this material.

    Nodular (ductile) is the choice for a stressed part like a steering knuckle or a crankshaft.

    Nodular will ring like a bell whereas grey iron will crack/shatter with the appropriately sized blow.


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