Cutting holes without a punch...especially large diameter ones...see the picture below...
I use a circle template...(a mechanical drawing/drafting tool from the last century)...a pushpin and sharp xacto knife...
Hold or tape the template securely in position...
Keep the pin tip in contact with the template...and punch a series of very, very closely spaced holes around the perimeter...
Remove the template...
These pin holes actually per-cut the cardboard...and if you cut slowly...just a short distance at a time...in multiple passes...the tip of a sharp knife will follow the location of the pin holes...
After cutting...and between coats of primer and paint I..."burnish" the inside edge of the opening to smooth it out if I notice any glaring irregularities...
This method works for me...with it I can cut any hole or radius needed...but I still use round punches for most holes up to about 1-inch or so...
Hope this all makes sense...
My very best regards...Howard...



























