Enlarging a bulkhead hole in acrylic

[ReefDreamz]

My acrylic sump has a hole drilled for a 1" bulkhead but I need to enlarge the hole to fit a 1.5" bulkhead. Obviously if I use a hole saw with a centering bit there is already a hole so nothing for the bit to drill into. The hole saw will jump around and create a mess. Is there a secret method for this situation? I was thinking maybe make a template out of wood with the larger hole in it and clamp it to the top of the sump then drill the sump through the wood template to stop the hole saw from moving.

 

[RichReef]

The best way is the way you suggested.

Drill a hole in a piece of wood. Lightly clamp it to the acrylic or get another person to hold it or both. Use water to cool. Once you get it started you are golden. Drill baby drill. The only thing to watch for is whether or not your bit is tapered. If it is at some point the wood will become obsolete and a steady hand is needed. Spin slow.

 

[albano]

The best way is the way you suggested.

+1… done it a few times!

 

[RichReef]

You could also clamp 2 pieces of acrylic on each side of the hole so your guide bit can be used.

 

[A_Blind_Reefer]

Depending on your holesaw setup, if your running a mandrel with interchangeable bits, you can install the larger holesaw on the mandrel and the smaller holesaw (the same size as the original hole) inside the larger holesaw. I do this all the time with Lenox, Milwaukee, and dewalt mandrels.

 

[b2smoov]

+1 for above reply.