Why Cast Iron?

H

HBilly1022

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I look at the parts of my Chinese lathe and see that almost all parts are made of cast iron and wonder why. The reason I'm asking is that if a part wears out I thought to replace it with something I made with mild steel, rather than order a new part from the manufacturer (whose prices are absurd). Besides, making the part would be more satisfying. Some of the parts I'm thinking might wear out are the tension bar and slide bar for the saddle.
 
as far as I understnd it is because cast iron absorbs vibration and is pretty hard, a cheaper alternative i've heard good things about is granite resin
Its fairly difficult to find something that dampens vibrations /and/ is hard enough to not wear out quickly
 
Look up mechanical properties of gray iron- Atlas Foundry Company. You will find that grey iron has much greater damping of vibration of other metals including steel. And this would somewhat even include Chinese iron unless it's white cast iron.
Metal said:
as far as I understnd it is because cast iron absorbs vibration and is pretty hard, a cheaper alternative i've heard good things about is granite resin
Its fairly difficult to find something that dampens vibrations /and/ is hard enough to not wear out quickly
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Iron is soft. Drill or mill it and watch the powder pile up. Softness equates to the ability to flex at a molecular level and dampen vibration. It's also cheap and easy to cast. Old School mindset, but as long as it's cheap who cares right?
 
It is a stable material, it does not move around much over time when thin sections are involved, it is also easily cast into complex often hollow shapes.
You will notice that virtually all machine tools are made from cast iron.

Additionally there are many different alloys of cast iron intended for particular applications, the iron used in your Chinese lathe is likely not the same as employed by say Hardinge , Mazak and LeBlond.
 
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Wreck™Wreck said:
...the iron used in your Chinese lathe is likely not the same as employed by say Hardinge , Mazak and LeBlond.
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I'll bet you're right about that.

I found cast iron machines very easily and cleanly but by my real question is; can I replace a wear part on my lathe with mild steel or will that cause damage to the mating part. In this particular situation I am referring to a replacement saddle tension bar being made of steel and rubbing on the underside of the bed ways. The top of the ways is supposedly hardened but I highly doubt the underside is and that is where the tension bar rubs. Maybe I should use aluminum. It would wear before the cast iron (I think), which would preserve the bed ways.

This all hypothetical at this time but curious minds (well mine anyways) want to know.
 
HBilly1022 said:
I'll bet you're right about that.

I found cast iron machines very easily and cleanly but by my real question is; can I replace a wear part on my lathe with mild steel or will that cause damage to the mating part. In this particular situation I am referring to a replacement saddle tension bar being made of steel and rubbing on the underside of the bed ways. The top of the ways is supposedly hardened but I highly doubt the underside is and that is where the tension bar rubs. Maybe I should use aluminum. It would wear before the cast iron (I think), which would preserve the bed ways.

This all hypothetical at this time but curious minds (well mine anyways) want to know.
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I suspect that using a lathe at the frequency that a hobbyist would, (not running the carriage up and down the ways 8 hours per day, 5 days per week or more whilst making the maximum cut the the machine will handle) mild steel used in this application would not wear out the machine before you were worn out.
 
Use ductile iron in place of the cast iron is my preference when rebuilding "broke" components made of cast iron. The dura Bar line of 55-06 ductile iron is twice the strength of cast iron and the ductility in the D.I. is less likely of breaking as you see in C.I. Much better choice than using mild steel.
 
Wreck Wreck, you're probably right and I guess time will tell.

4gsr; thanks for the tip. When I need to replace a broken part I will check out D.I. I know D.I. is used a lot for watermains and basically replaced Cast Iron because of it's ductility and strength.
 
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