Cutting a round hole in fiber cement board

[Oldoak]

I used a 4" (Milwalkee) bimetal hole saw on thin stainless. Messed up that saw in a hurry. Much regretted. Thought with plenty of SS cutting oil it might be OK. It won't cut nothin now!

When using a hole saw or band saw on stainless steel, very slow RPMs or slow band saw blade speed along with a cutting lubricant and steady light even pressure gets it done without a problem. More often than not teeth are ruined by too high of drill or sawblade speed.

Although a 4" hole being cut with a hand held drill in thin SS sheet metal can be a little difficult. Not a problem using a drill press.

 

[spitter]

Score Durarock with Durarock knife or utility knife punch out hole with hammer . That's the fastest easiest way . Or if you have a sheetrock router buy a carbide bit . Scoreing and hammering is the fastest easiest way done miles of it in restraunts , hospitals and schools.:thumbsup::drink:

 

[Lineman North Florida]

Score Durarock with Durarock knife or utility knife punch out hole with hammer . That's the fastest easiest way . Or if you have a sheetrock router buy a carbide bit . Scoreing and hammering is the fastest easiest way done miles of it in restraunts , hospitals and schools.:thumbsup::drink:

This is Hardie board exterior siding so I'm not sure if scoring it would work but it might,I'm basically cutting through 1/2 sheetrock then 7/16 OSB and finally the hardie board exterior siding. Thanks for all the replies from everyone.

 

[wagne223]

This is Hardie board exterior siding so I'm not sure if scoring it would work but it might,I'm basically cutting through 1/2 sheetrock then 7/16 OSB and finally the hardie board exterior siding. Thanks for all the replies from everyone.

When you said fiber cement board, I as well as others obviously, assumed you meant durock or some brand of concrete backer board.

With hardie board, use a holesaw designed for concrete, brick, and tile.

 

[Lineman North Florida]

When you said fiber cement board, I as well as others obviously, assumed you meant durock or some brand of concrete backer board.

With hardie board, use a holesaw designed for concrete, brick, and tile.

Yeah I should have said siding instead of board, sorry if I made it confusing to anyone.

 

[cycle_gator]

Whatever cutting tool you decide to use, I would start the hole on the Hardi-Board side, you will get a much smoother cut. For me, I would use the bi-metal and just accept that I shortened its life. However there are some good carbide tipped hole saws that will handle that well. Like Eddie said, watch out for the grab.

 

[EddieWalker]

This is Hardie board exterior siding so I'm not sure if scoring it would work but it might,I'm basically cutting through 1/2 sheetrock then 7/16 OSB and finally the hardie board exterior siding. Thanks for all the replies from everyone.

Next week, I have to drill three 4 inch holes through OSB and Hardie Lap siding. One for a shower vent, one for a toilet vent and one for a laundry room dryer vent. My 4 inch hole saw is a Bosch, and I've used it on Hardie at least a dozen times. I've also used it on sheetrock more times then I can remember. This is my second one. I doubt the three holes that I will drill next week will ruin it, but if it does, I'll replace it and keep using it until it wears out again.

My drill is an 18 volt Makita cordless with an attachable handle. I use it at the slow setting, and kind of rock the bit from side to side, up and down, while drilling to clean out the teeth.

To seal up the hole when installing the vents, I will use Leak Stopper from Lowes. Henry has a good one too that's sold at Home Depot, but I like Leak Stopper the best. It's in the roof flashing area of the store. It goes on white, and dries clear. Then it holds paint great, but what's best about it is how well it holds everything together. In a year, try taking it off and you'll understand why I like it so much.

https://www.lowes.com/pd/LEAK-STOPPER-10-1-fl-oz-Waterproofer-Cement-Roof-Sealant/3013307

 

[Diggin It]

Whatever cutting tool you decide to use, I would start the hole on the Hardi-Board side, you will get a much smoother cut. For me, I would use the bi-metal and just accept that I shortened its life. However there are some good carbide tipped hole saws that will handle that well. Like Eddie said, watch out for the grab.

I'd do it from the inside out ... partially. Use the regular hole saw from the inside to get through the softer materials. Go just far enough for the pilot bit to cut through the outer material. Then go outside with the carbide hole saw and use the pilot hole as a guide. You end up with smooth holes and no breakout on both sides.

 

[hawkeye08]

I bought some holesaws from Amazon for our bathroom tiling project.. we were pleased with results. We put the tile in a paint pan with water but a spray bottle will work also.
https://smile.amazon.com/Diamond-Countertop-Porcelain-Bathroom-Installation/dp/B07481K6DG/ref=pd_day0_hl_469_5?_encoding=UTF8&pd_rd_i=B07481K6DG&pd_rd_r=e1971e4f-2635-11e9-8d89-2156212e8c69&pd_rd_w=J8gr5&pd_rd_wg=HL2bC&pf_rd_p=ad07871c-e646-4161-82c7-5ed0d4c85b07&pf_rd_r=NGQZM9BPNKH7P9JNCEG1&psc=1&refRID=NGQZM9BPNKH7P9JNCEG1

When I cut the hole in the hardi board I used a rotorzip with circle attachment.. doubt that would work for your project.. The Drilax link above does not have a pilot bit, so care must be taken to get it started right.. like Eddie says rocking it while cutting works, to start though, angle it a bit so one side starts cutting, otherwise it walks all over the place with no pilot... For your project, I would likely use a bimetal holesaw, get the easy stuff first, do the hardi board last. Heat is the enemy of holesaws, try not to overheat whichever way you go..

 

[oosik]

Hey, man up. 12 gage at about three feet. No - I've used a metal cutting blade in my cordless reciprocating saw. I consider the blade a goner after about three feet of cutting. Cement board is tough on blades.