at the front view, holding SHIFT to make a circle from the centre of the coordinate

click the hollow red square, hold OPTION to duplicate and hold SHIFT to scale proportionally

file>setting>grip snap>snaping space > 0.1

move the big circle upwards a bit

at the right
view, ellipse from centre, make a line, get the arc by trimming

command:arc>start point

i am trying to fillet two curves, yet somehow it does not work. it takes a long time to trouble shooting and detect the problem.

I finally found out these two curves lines are not on the same plane, and thus i creat the arc line again with planar bottum on.

if the fillet radius is too big, filleting may also not function. the left is made by radius 1, and the right one is radius 0.01, base on the unit that I chose is 1 centermetre

go to front view, which is much easier to click all the line. press shift to proportionally scale it.

transform>rotate> enable copy, setting the point as 0, holding shift while rotating

command:scale1D
streach it to the verge of the circle, then mirror it by rotating, point 0, shift

group the comb-like graphic, activate HISTORY, command:sweep2, click all the component

PLUS WEEK

click "close the ring"

MAKING A RING BY RHINO

drag the half part, and twist