Shop furnace flue

[danl]

I need to cut a 9" round hole in a 12" culvert to use for a flue in my shop.

The old one lasted about 8 years, I didn't have a cleanout on it and my fault it rusted out.

I had a hard time cutting the hole the right size in it last time and was hoping someone had some pointers on how to do it.

I had tried cutting a paper template 9"round, but that didn't work.. I figured that out the hard way.

Thanks
Dan

 

[KsWoodsMan]

Butt a long 9" piece up to the 12" where you want the hole. Put a flashlight centered inside the 9" tube pointing to the 12" culvert. Use a marking pencil, soapstone or permanent marker to mark the opening where you want the hole. Cut out the hole.

If you want a tighter fit cut the hole 1/2" smaller than the marks. Make 1/4" cuts radiusing out from the middle to the first mark you made and bend these 'tabs' in or out depending on how you intend to attatch the 9" collar.

It should be pretty close.

 

[danl]

Thanks, I'll give that a try. I never would have thought of that.

On the first pipe I went to lot of trouble to tape the template on the culvert and marked it carefully and couldn't imagine why it didn't fit.

I guess wrapping the template around the culvert was my mistake.

 

[KsWoodsMan]

after the first hole was in there and too narrow on the sides you could lay the templace in the hole and mark out where you needed it bigger. It would give you 2 cresent shaped pieces when you were done.

Lots of ways to get there, someone else might have an idea or method of dooing this that blows mine out of the water.

I'm not sure how you are going to seal that up , I figured you had that part covered.

I have seen a couple of hose clamps around the 9" flue and a piece of plumbers strap around the 12" with the ends folded back over the clamps keep something similar from falling out. The adjusters on the clamps were at the top and bottom to hold it against the 'culvert' to keep it from going in too deep. Worked good for holding it if the strap was just a bit short. Didnt do much to seal it though.

YMMV , good luck with the project.