They are fun to make, almost addictive. I experimented with different gauges of wire and sizes of mandrels. This is the 3rd try.
Here's a comparison:
The tutorial in the link above has a chart showing the wire gauges and ring's inside diameters (ID).
This reminds me of the pure wool logo.
**** Update. April 17, 2014 ****
I'm very happy to see many of my readers finding this post worthy of their visits. Thank you so much!! If you have any questions, please drop a note or leave a comment here; I'll do my best to help. BTW, I did make all these Danish knots (as well as all the handcrafted pieces on my blog site), and I did take all these photos myself, therefore I do hold the right to these photos and their uses; you're more than welcome to share with back links to my posts; and in the case if you do ask to use my photos with credits, I'd most likely be thrilled and even help you spread the words!! So, I'd appreciate it if you don't just download them and repost them as your own in your translated "tutorials" or web pages. That's just not cool :-(