Cutting a round hole in fiber cement board

[coldsteelva]

Start with the hole saw on the outside IN REVERSE - to score the surface before going in the correct direction. This should prevent the teeth from wandering once it bites into the Hardi. I have this siding and it is really durable, but you have to keep tapcons on hand if you ever want to attach anything to it.

 

[EddieWalker]

Start with the hole saw on the outside IN REVERSE - to score the surface before going in the correct direction. This should prevent the teeth from wandering once it bites into the Hardi. I have this siding and it is really durable, but you have to keep tapcons on hand if you ever want to attach anything to it.

Never tried that. I drill from the inside because I know where I have to be to get everything lined up. Then when I'm well into it, I might go outside to finish the hole. The pilot drill bit allows me to stay in place. I've never had a hole saw wander. I've also never had any issues with destroying the Hardie on the outside when drilling from the inside. The only reason to drill from the outside after I've started on the inside is personal comfort. It can be very awkward laying on rafters and reaching to where I need to drill the hole.