There's a lot of controversy about using WD-40 on sewing machines. Let's talk...
I use WD-40 on sewing machines, almost every day at work. However, I don't use it as a lubricant, I use it as a solvent. WD-40 breaks down the old, gummy oil very well. If you're not equipped to remove the WD-40, it will continue to break down the oil. At work, we use an air compressor and flannel rags to remove the WD-40 and the gunk it dissolves. If you don't have an air compressor, you can use a can of air -- but it has to be a full can with some good pressure.
Don't use WD-40 on certain longarm quilting machines and industrial sewing machines. Some of these have porous bearings that will hold onto the WD-40.
The procedure goes like this...
1) Blow out all the lint with an air compressor.
2) Generously spray the gummed-up area with WD-40.
3) Work the mechanisms until they are moving freely.
4) Blow out the WD-40 and gunk with an air compressor. This takes a while. You continue to blow until there are no more wet spots. Turn the hand wheel to get all sides of the sprayed parts.
5) Wipe up the mess with flannel rags.
6) Go back and blow some more with the air compressor.
7) Apply new oil. Only use clear "sewing machine oil," not 3-in-1 oil (or sewing machine grease except for very specific spots).
Some people will say that "someone" told them to NEVER use WD-40 on a sewing machine. But I have to ask, who is "someone?" And was "someone" talking about using it as a lubricant? This "someone" LOVES to use WD-40 on sewing machines! It works very well to remove the gummy stuff.
I've also seen where "someone" used WD-40, and it made matters worse. I think they probably didn't use enough WD-40, and didn't get the gunk dissolved completely. So, the gunk was still there.
I've only had 5 years (almost) of experience, but have never had a problem with WD-40 making things worse.
Some may say to just keep oiling the machine, and it will eventually break loose. Nonsense! The old, gummy oil is still there! The old gummy oil needs to be removed, and WD-40 is the tool for the job.
OK, there's my very own, personal, private, take on the WD-40 controversy. But then, I tend to figure things out and think for myself. I know I'm not the only sewing machine mechanic who uses it!