*NEED HELP FAST* 8" Thimble How Big a Hole?

 
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beatle78
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Post by beatle78 » Mon. Dec. 22, 2008 2:01 pm

I am chimney retarded.

I just bought an 8" thimble with an O.D. of 10".

I can either have a 10" or a 12" hole cut.

Do I cut the 12" hole and mason in the thimble?
or
Do I cut a 10" hole for a nice tight fit.

Thanks!!!
Jeremy


 
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beatle78
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Post by beatle78 » Mon. Dec. 22, 2008 2:01 pm

p.s. Sorry, I posted to the wrong sub-forum.

Please move to Chimney forum!

 
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Post by CapeCoaler » Mon. Dec. 22, 2008 2:21 pm

12" hole.
If you do a 10" hole you will not have any room for mortar.

 
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Post by beatle78 » Mon. Dec. 22, 2008 3:32 pm

ok, thanks. I just ordered the 12" hole!

This is LOOOONG overdue! Hopefully I'll be on coal before the new year!!!!

 
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Post by coaledsweat » Mon. Dec. 22, 2008 5:13 pm

Make sure it is going uphill.

 
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Post by beatle78 » Tue. Dec. 23, 2008 11:24 am

coaledsweat wrote:Make sure it is going uphill.
The thimble needs to go uphill?

The thimble on my other flue goes straight through. I assumed the draft takes care of the rest. Yes/No?

 
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Post by CapeCoaler » Tue. Dec. 23, 2008 11:42 am

12" hole.
Slight pitch to the pipe.
That is what the extra 1" is for, mortar and adjustment to pitch!


 
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Post by beatle78 » Thu. Dec. 25, 2008 11:43 am

ahhhh... ok so they can drill a straight 12" hole and I pitch it with the mortar! Got it!!!

Concrete cutting tomorrow!!!! WHOHOOOOOOO!!!!!

And not a moment too soon! My oil tank is running on fumes! :shock:

 
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Post by Dann757 » Thu. Dec. 25, 2008 3:05 pm

I traced around the thimble onto the chimney block with a sharpie while holding it in place centered. Then drilled 1/4" holes all around into the block, outside the trace line. Carefully chiseled the block. The old mortar was much harder than the old block. When I got to the flue I carefully drilled shallow holes all around and nibbled it larger with an adjustable wrench. I was careful not to hit it for fear of cracking it. The hole was big enough to position the thimble, which I cut down to 8" long. I buttered the flue and thimble end with refractory cement, and set the thimble on a trowel full of mortar while mating it to the flue. Supported it with a 2x2 just to be sure.
Then I packed in mortar with a small trowel and a piece of cove molding. With the baro so close I can check the refractory cement joint any time.

Attachments

Picture 040.jpg
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thimble front.jpg
.JPG | 21.3KB | thimble front.jpg

 
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Post by beatle78 » Thu. Dec. 25, 2008 9:15 pm

Dann757,

Thanks for the pics!!

OK, I have some questions.

1. What did you use to cut the thimble?
2. how did you marry the thimble to the clay liner? *Did you just get it close and fill the joint with cement?
3. What is refractory cement? (is that a special kind of cement that I need to use?)

Thanks!
Jeremy

 
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Post by Dann757 » Thu. Dec. 25, 2008 11:16 pm

Jeremy,

I have a Plasplugs tile saw that I've had for years. I got it at Home Depot. It is a wet saw, I took the blade guard off and the blade is just high enough off the table to cut all the way through the thimble. Inexpensive tile saw, it's been very durable. With the fence on it, it cut the thimble perfectly. I also cut my firebricks with it that way. Both these materials can take a lot of heat, but they're not hard to cut. You could also use a masonry blade in a circular saw, or a diamond blade. Refractory cement is very high temperature cement, that isn't water soluble. It cures like cement. Mason supplies or stoneyards have it. I buttered the flue and thimble pieces with a nice thick amount of refractory cement, and pushed them together to form a complete mating seal. Then smoothed out the cement. The thimble was under $20, the refractory cement was around $20. I'm another one of these guys that has to do everything himself.

 
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Post by CapeCoaler » Thu. Dec. 25, 2008 11:31 pm

The thimble should have gone past the liner outer shell.
If the refactory fails....

 
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Post by Dann757 » Fri. Dec. 26, 2008 9:27 am

CapeCoaler,

I wish I could have put the thimble past the liner. I wanted to match the diameter of the stove breach, 8". The chimney liner is nominal 8", the thimble nominal 8". I didn't want to drop to 6" thimble and therefore 6" stovepipe. I check the joint daily, it's intact now, will be continue to be intact unless there's an earthquake. The seal between the thimble and liner is solid, and the thimble is totally retained by being mortared in place. What I intended was to run the 8" stove pipe through and splay it out into the liner. The first thimble I got had a factory hairline crack on the outside so I got another one off the pallet at the stoneyard. The first one was 8-1/8" ID, the second one was 8" ID, I think due to quality control. So I couldn't direct fit the stovepipe through the flue without modifying it. I should do that just for extra safety. I have two thermometers on the T and thimble. It hasn't gone over 200* f.

 
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Post by beatle78 » Fri. Dec. 26, 2008 11:29 am

ok, so ideally we want to put the thimble past the liner and cement around the outside of the thimble?

Nice idea about the tile saw. I'll have to go get mine and use that... BRILLIANT!

2 hours and oucnting until the chimney gets cut.

 
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Post by CapeCoaler » Fri. Dec. 26, 2008 12:53 pm

Yes in a perfect world the thimble would be flush with the inside face of the chimney flue tile.
You want a smooth transition and no restrictions for the flue gasses.
Slight pitch up towards chimney is nice but not necessary if it is just a short section.
1/4" in 10' like a drain pipe.


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