a lady I know who works on older machines, treadles, handcranks, and older electrics says to never use wd-40. Instead use Liquid Wrench. Wd-40 will eventually leave a sticky coating she says. LW has kerosene in it and doesn't leave a coating. If a machine is really locked up and is all metal she'll soak the whole thing in a tub of kerosene. of course I've also read somewhere to never oil a machine with plastic parts in it period...that the oil deteriorates the plastic.