Originally Posted by Rodney

I'm trying to figure out if the second one has crinkle paint over the original finish or if that's some rusty cast iron showing thru. Either way you have your work cut out for you on that one. If it's rust, the WD-40 might help loosen things up but after everything is freed up clean it off and oil the machine properly. WD-40 has it's uses but it's not a great long term lubricant. Kroil is one of the best penetrating oils to use on stuck parts or a 50-50 mix of automatic transmission fluid and acetone works well too. Any one of the above can be hard on the finish and decals on a sewing machine though. That's why sewing machine oil is recommended. It won't harm the finish.
Rodney