If you mean the border, the inside line is created by riding the scriber around the bead, the other two lines can be marked with dividers with one point in the cut but I just draw them by hand.
Thank you for letting us see this wonderful action packed design at the early stages! It never fails to be a treat when we get to see you take the cylinder head off and allow us a look at how your 'engine' works.
Its been a while since I saw Rolf Harris, a creative Aussie with a big paint brush and huge canvas, as well as a fine entertainer. He really did make it big on the UK telly. I knew him in the old days in Vancouver. I worked the Inquisition club and he worked the Arctic Club. We sometimes had lunch together, I found him to be a very decent human being who did not ration his funny side only for the stage, could not stop laughing long enough to eat my fish and chips. Wonder what he is doing these days?
Didn't Rolf paint a controversial portrait of Liz the 2nd???
I'll never forget Rolf's version of Stairway To Heaven while he's playing the wobble board. That was something else!!!!. And what can you say about Jake The Peg after a rousing rendition of Tie Me Kangaroo Down Sport..................classic