This section is from the book "The English And American Mechanic", by B. Frank Van Cleve. Also available from Amazon: The English And American Mechanic.
Fig. 12.
To cut for pitched covers, draw a circle one inch larger than the hoop is in diameter after burring, then draw a line from the centre to the circumference as in the figure, and one inch from the centre and connecting with this line draw two more lines, the ends of which shall be one inch on either side of the line first drawn, and then cut out the piece.
 
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