You can use WD40 on just about anything metal, Knitting Machines being one of them.
What oil can I use on my knitting machine?
I use and highly recommend Singer Sewing Machine Oil™. It is a widely available, highly refined, fine grade of machine oil and it does not break down at a high rate. I use nothing else and it has served my knitting machines very well for years.
How do you remove knitting needles?
Grab hold of the back end of the needle and raising the needle up in the back while pulling up and towards the back – they should pull out and clear of the needle guide slot. To replace needles, simply reverse the process (and needle latches should now be open).
How do you clean metal knitting needles?
To clean the needles use a standard metal polish, work it well over the whole needle and rub off the polish with a soft cloth. You may need to repeat this several times to remove all the dirt, especially if the needles are old or well used.