Castings vs Steel ?

[Rick SpaidalParticipant @rickspaidal44040]

I am new here and enjoying this forum !

my question is why are so many parts made from

castings (so cast iron) vs steel

is cost the only reason? I see castings are not that cheap

I give a face plate as an example, whats wrong with machining

one out of steel, or the cross slide of a lathe, they are cast as well

but could be made out of steel

 

TIA

[Rick SpaidalParticipant @rickspaidal44040]

[Chris BParticipant @chrisb73862]

It just depends on where you are starting from, there is nothing wrong in making things in steel or any other bar stock, but this can be quite time consuming and produce lots of swarf!

On the other hand castings give a basic shape that just needs the relavant surfaces machining, with less waste.

Buying “commercial” castings gives you the time saved in machining away the waste you would have had if you machined from solid, but you pay for an element of the pattern making costs plus transport costs.

 

If you are fortunate enough to have a local foundry then making your own patterns will pay dividends especially for mutiple items as the costs are a lot more reasonable.

Edited By Chris B on 29/01/2010 22:31:27

[Geoff SheppardParticipant @geoffsheppard46476]

I recall being told (many years ago!) that cast iron was the preferred material for machine tool structures (lathe beds etc) because the structure of the material possesses damping qualities which absorb vibration better than steel. Try suspending a bit of steel and hitting it with another piece of metal, then do the same with a bit of cast iron.

 

[Rob ManleyParticipant @robmanley79788]

Cast Iron is also one of the few materials that is ideal for sliding against itself.  Cast Iron on cast iron yes, steel on bronze yes, steel on steel gives poor wear qualities.  A machine tool would be worn in less than half the time if its sliding surfaces were made of steel.  A cross slide is quite a simple shape but because of the wear properties would make steel unsuitable.  Something like a faceplate, if it were of moderate diameter would be extremely heavy in solid steel – a cast one is lighter with cast in strengthening ribs etc. There are many more reasons for the use of cast iron which im sure others will say.  Its also a lovely material to work with aslong as you make sure you get all the dust off your machines – It does not help lubricate the slideways as i heard one person say!

Cast iron will always have a major place in engineering, its just a pity our smaller foundries are disappearing. 

 

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