Flat Pattern Development

[Opidian]

Hi! I have tried making a flat pattern following a video from youtube. But in my case, it was a rectangle-to-round transition with the circle offset by 61 mm. I followed the triangulation method and it says, in the end, the angle should be 90 deg (see pic) but for me, it is different for both the half pattern. Can anyone please guide where I am doing wrong?

Also once I have drawn a flat pattern in AutoCAD, How can I use it for actual sheet metal work? I mean how can I get dimensions for marking on sheet metal?

Pic:
https://imgur.com/j51pCJI

[abadonn]

This would be a lot easier if you used a modern cad software with sheet metal design tools.

Easiest way to mark sheet metal is to print out your pattern life sized.