I've removed my kitchen tap's aerator and put on this dishwasher adaptor https://www.bunnings.com.au/kinetic-19mm-brass-dishwasher-adaptor_p4920392.
However, now I cannot unscrew it. I have already tried
1. Twisting adaptor both anti-clockwise and clockwise to make it move - neither direction move the adaptor
2. Using a vicegrip to hold the adaptor and twist - vicegrip moves itself, rather than the adaptor
3. Gently warm adaptor up with strong hair dryer
4. Spray some WD40 over the joint between tap and adaptor
Welcome to the Workshop community @junhandy. Many thanks for you question, I'd be happy to advise.
I have just spoken to one of our team members in-store and can confirm the thread is standard and not reversed. When you have the vicegrips locked onto the adaptor you will be moving them to the left to unscrew. The internal threads are quite fine on that fitting and they have potentially cross-threaded causing the issue.
I will make contact with Kinetic on Monday to find out what would be the best solution to this issue and will let you know of their response.
Have you made any progress towards removing the fitting by ensuring you are undoing it in an anti-clockwise direction? I've just spoken to Kinetic and they have advised the fitting is to be installed by hand. They are unsure as to why you would not be able to remove it by hand or with vicegrips as you have mentioned.
Please, let me know how you go and we can continue to advise on a solution.