trainguy

So I've got this renovation project...

I need to cut 4 holes through the exterior wall for two new bathroom vent fans, one new kitchen exhaust hood and one new kitchen intake, all of which will be for 6 inch sheet metal duct. Exterior wall construction is 3/4" grooved "board" (which I am reluctant to call plywood as it does not look like modern plywood) covered in a traditional stucco finish (the house is over 100 years old). From my experience, there is no underlying metal/diamond lathe except where small repairs were done.

Here are my questions:

1. I am assuming that I will need to cut 6-1/4" holes for a nominal 6" diameter rigid SM duct.

2. I figured that a hole saw would make the cleanest hole and I assumed that a diamond grit would be appropriate for stucco (understanding that it is similar to masonry). The problem is that I am having a hard time locating a 6-1/4" hole saw that I can chuck in a drill motor (with or without a mandrel) that has a diamond grit (the diamond grit hole saws that I am finding are for concrete coring applications). I have read that I can use carbide but they wont last as long and the holes will take much longer to cut.

3. If I use a carbide or diamond grit hole saw, once I get through the stucco and reach the wood underlayment, then what? Do I need to change to a different type of hole saw (or saw type/blade)?

4. Is there a better alternative to the hole saw approach, i.e. recip, oscillating tool, rotary cutout, etc.?

Thanks in advance, all!
Jimmy

ClarenceBauer

You can find a masonry hole saw 6.29 Dia. that will fit most heavy duty drills. Look for Bosch Concrete ,porcelain & Marble drill bits. Once you get through the Stucco & lath you will need to switch to wood cutting bits or blades.

trainguy

Clarence-

Thanks! I went to the Bosch website but I was not able to find such a product in the size that I need.

Jim

ClarenceBauer

https://www.amazon.com/Agile-shop-Di.../dp/B077H33S6H

trainguy

Thanks, Clarence! Not a Bosch product but the correct size and type nonetheless!

Jimmah!

Nealtw

His link goes to 160 mm, that is 6.29 inches????


https://www.rapidtables.com/convert/...m-to-inch.html




You may want to finish the hole with a jig saw.

__________________
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trainguy

Neal, you are absolutely correct. The diameter is fine, I just mentioned that it wasn't a Bosch product, that's all. The one that Clarence linked to is $19. Considering that these four holes will probably be the only four that I cut through stucco in my house, if that sucker makes it, it was worth every penny less than what the Bosch version would have cost!

Thanks all!