grazing muzzles-enlarging hole

[mtj]

Please can someone advise on how to do this without producing sharp edges. Thanks

 

[teasle]

File cut edges with a nail file.

 

[milliepops]

^^ yep, I've also used a leather hole punch in the past if I don't have a knife that is sharp enough to get it started You can make lots of small adjustments then without the risk of chopping your arm off!

 

[mtj]

Thanks for the suggestions.

Would never have thought of a hole punch, and also do not trust myself with a proper blade.