There are a few schools of thought when it comes to the angle you should grind your parting tool. Some people recommend grinding at a bevel angle between 30 and 45 degrees, while others recommend using a shallower angle between 10 and 30 degrees.
Personally, I think the best angle to grind your parting tool depends on what material you're working with. If you're working with softer materials like wood or plastics, then a shallower angle will work just fine. However, if you're working with harder materials like metals, then you'll want to use a steeper angle so that your tool can bite into the material better.
Ultimately, it's up to you to experiment and see what works best for you. Different angles will produce different results, so it's important to find what works best for the material you're working with and the results you want to achieve.