1. Draw the outer circle with a diameter of 120mm (radius 60mm.)
 

2. Draw the inner circle with a diameter of 100mm (radius 50mm.)

3. Draw the two lines from the centre point as shown to give an included angle of 80º.
 
 

4. Top line is at 40º while the bottom line is at 320º (-40º).

5. Draw the centre line as shown opposite. 
 

6. Drop a vertical line from point "P" on the inner circle to the base-line.
 

7. Draw a line from the bottom of the R60 circle to point "P" and extend it to the outer circle.

8. Draw a horizontal line 45mm from the base line.
 

9. Draw three more horizontal lines each 10mm apart as shown opposite.

10. Draw the parallel line 16mm from the circle as shown.

12. Draw another parallel line as shown.

13.Tidy up the image as shown.

14. Apply appropriate shading (yellow) if desired.