Charles A. Sherwood wrote:
What are the machining properties of 4130? Perhaps this is the best
compromise between finish and toughness?

4130 is a crome moly steel. Tough to turn; especially when compared
to leaded steel. Not exactly cheap to buy either.

I picked up a large bar of steel that appeared to be hot rolled.
It machined easily after removing the crusty surface. Sometimes
cold rolled (1018) machines well and sometimes it is tought to
get a good finish.

chuck

I buy my steel from JM TULL its a large steel company here in the US
and this is the discription of 12l14 in there catalog."Tull-led
12L14 provides superior machining properties,high cutting speeds, and
incresed tool life .Surface finish is uniformly smooth and bright .
parts close size accuracy the addition of lead has no efect on the
mechanicl properities or the internal soundness of the steel."
Here are the mechanical properties the catalog gives for
cold finished rounds.

1018 tensile psi 64,000 yield 54,000 elongation in 2 inches 15%
12L14 tensile psi 78,000 yield 60,000 elongation in 2 inches 10%
1144 tensile psi 108,000 yield 90,000 elongation in 2 inches 10%
4140 annealed tensile psi 102,000 yield 90,000 elongation in 2
inches18%
4140ht (heat treated rockwell 28 to 32)tensile psi 125,000 yield
105,000 elongation in 2 inches 16%

The 12l14 is not as tough as 1018 but has a higher tensile and yield
properities.Agian before anyone flames me these figures came from the
manufactures catalog.
Here is my thinking 1018 is junk metal its hard to cut and get a good
finish I try to avoid using it unless I have to weld it .
Most other alloys don't weld very well.