The main advantage (in my mind) of cast iron for machine building is the damping effect it has, where as steel tends to resonate. Many machine parts are castings. Cast iron contains free graphite which is a lubricant. Cast iron can be run as a bearing surface against either cast iron or steel.

I don't suppose you are going into mass production in a factory, I'd go for the steel option, if it's going on an existing cast iron lathe bed it should be spot on, if it is a home built lathe with a steel bed, use a good supply of oil on it, and it should be OK for many years of use.

Just my ideas.

Ian S C

It can be tuff stuff, disc brakes for cars for example

Nothing soft about bronze. For centuries after iron was discovered it was still the preferred material for knives snd weapons. Also brass. Look how often gib strips are made of brass and they then form 25% of the bearing surface.

You could also look up Moglice – homemade versions. Make all the structure out of steel or even cast some aluminium but arrange for bearing surfaces to be something else.

You could also consider something more complicated with ball/roller bearings Your choice of bed makes this viable whereas the point loading would be too much for a CI or plain steel bed.

There is another reason why cast iron is used. One of the reasons that casting things out of iron was so popular was that the process enabled shapes to be made that were otherwise not practical. It also enabled simple and even complex shapes to be made cheaply.

Everything that has been said so far is true, about the vibration damping etc, but never forget the cheapness of the process.

Also have a look at "Russian" lathes at everyones' favourite resource, I have one of these lathes and it is a really robust small lathe.

cheers

Bill