Mild Steel?

[Bob Korves]

I will add if you want to machine it try cold rolled it's a tiny bit more but it is actually really close to its stated size I've had hot rolled that was way off it also isn't covered in mill scale which is pretty hard on bits etc and for me machined better than hot rolled still not great especially with a small machine that can't take heavy cuts but it's cheap and plentiful to learn on

Correct, uma, cold rolled has better dimensional accuracy, better surface finish, less mill scale, and a bit more strength. The down side of cold rolled it that it has a good amount of locked in stresses from the cold rolling. If you take a bar, say 1/2 x 2" with some real length, clamp it to your mill table with the wide side down, and then cut 1/8" off the top to make it 3/8" thick, you can get a big surprise when you loosen the hold downs and the work springs into a banana shape. Hot rolled is much less likely to do that.

 

[4GSR]

Yeah, mill a 3/8 wide keyway down a 1" diameter C1018 shaft 9 foot long and see the results. Spent a couple of days trying to get it straight again.

 

[den-den]

I buy drops often, once got some 1-1/2" thick pieces that had been flame cut that were not mild steel. It could be drilled with a new bit (away from the flame cut area) but was hard to work with. Normally the drops are mild steel and even flame cut edges are not impossible to cut/drill.

 

[4GSR]

I buy drops often, once got some 1-1/2" thick pieces that had been flame cut that were not mild steel. It could be drilled with a new bit (away from the flame cut area) but was hard to work with. Normally the drops are mild steel and even flame cut edges are not impossible to cut/drill.

If they are plasma cut and they used nitrogen for barrier gas, the nitrogen will nitride the surface in the HAZ and yes it will be hard. Even on A-36 Plate.