Edge Margin for Drilling Acrylic

[atoz1to4]

What is a good egde margin to use when drilling a 1-3/4"dia hole (for a 1" bulkhead) in acrylic for either 1/4" or 3/8" thick material?

 

[1234]

If the question is how close to the edge of the acrylic can you drill to- normally I would go no closer than the size of the BH that I'm using. You need room for the flange to seat flush to.

hth