# Whats the best way to cut a hole in a clay flue liner.



## Seasoned Oak (Dec 19, 2012)

Im trying to install a clay thimble in a brick flue lined chimney.Removing the brick was easy. Clay liner is about 3/4 " thick. Sure i can bust through with a hammer drill but ill crack the liner to pieces.Im trying to make a nice clean 7" hole without cracking the liner .So far i tried a carbide hole saw(liner too hard) A oscillating tool with a diamond blade(too slow) a small diamond tip hole saw(frayed out the saw edges).


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## laynes69 (Dec 19, 2012)

I'm not sure how much room you have to work with, but when I cut our thimble I used a diamond blade on an angle grinder. I tried just about everything prior and nothing would dent it. The diamond wheel made quick work of the cut. I couldn't believe how hard that stuff is. Be careful, the edges can be brutal.


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## jrendfrey (Dec 19, 2012)

the guys who did my chimney cut the top piece of like with a skill saw and masonry blade worked great but the was straight cutting. i would first try the angle grinder and diamond blade if not enough room get really good masonry drill bits and drill holes around in a circle about quarter in apart and very gently tap the hole pie out. if the clay thimble doesnt fit perfect you could use refractory cement to make things pretty. i dont know if this will work but its what i would try


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## jrendfrey (Dec 19, 2012)

ps dont use a hammer drill


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## Seasoned Oak (Dec 20, 2012)

Masonry bits dont work unless i can find a diamond masonry bit.


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## Corey (Dec 20, 2012)

When I had to cut through 8" of solid concrete plus a cinder block wall for the gas flue in the basement, I rented a 7" coring saw and drill.  Made quick and very neat work of the hole.   Might be overkill for just the 3/4" liner, but if you want it done neat and fast...

http://www.dexpan.com/core-bit-diamond-core-drill-bit-tb700.aspx


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## Seasoned Oak (Dec 20, 2012)

jrendfrey said:


> ps dont use a hammer drill


As i said a hammer drill will work but cause a lot of damage to the liner. Im looking for a nice clean cut.


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## Seasoned Oak (Dec 20, 2012)

Corey said:


> When I had to cut through 8" of solid concrete plus a cinder block wall for the gas flue in the basement, I rented a 7" coring saw and drill. Made quick and very neat work of the hole. Might be overkill for just the 3/4" liner, but if you want it done neat and fast...
> 
> http://www.dexpan.com/core-bit-diamond-core-drill-bit-tb700.aspx


You gave me an idea ,i have a 2" diamond tipped hole saw i use in plaster for drilling insulation holes ill try that. May be able to drill a series of smaller holes. I know a grinder with a  4"  diamond blade will work as well.


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## Adios Pantalones (Dec 20, 2012)

Diamond blade on an angle grinder. I use a diamond blade on a skil saw to cut bricks, but you'll probably need the angle for this one


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## Seasoned Oak (Dec 21, 2012)

Adios Pantalones said:


> Diamond blade on an angle grinder. I use a diamond blade on a skil saw to cut bricks, but you'll probably need the angle for this one


Those can be hard to control.I have both a 4 and a 7" angle Grinder. A few months ago i cut a nasty gash in my hand with the 7"  trying to cut a cast iron pipe in half when it jammed.


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## Seasoned Oak (Dec 21, 2012)

Regular masonary products do not work. Need diamond tipped tools for granite,marble ,quartz type stone ect.


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## raybonz (Dec 21, 2012)

How about carbide grit jigsaw blades?


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## Ralphie Boy (Dec 22, 2012)

This works well for puttings holes in most anything




I took this picture in Mons, Belgium during their 2010 Tanks in Town celebration. Its an event that takes place every year to celebrate the town's liberation by American forces in WWII
(U.S. M 10 tank destroyer)


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## Seasoned Oak (Dec 22, 2012)

raybonz said:


> How about carbide grit jigsaw blades?


I have all kinds of carbide tools ,this stuff is too hard for carbide,like granite or quartz you need diamond tools for it


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## Seasoned Oak (Dec 22, 2012)

Update: Well the 4" diamond blade on an angle grinder did the trick .Like a hot knife thru butter. You got to be very careful though,those angle grinders are hard to control and i did get hurt with one a few  months ago. Probably the very best way would be to rent a 7" diamond hole saw bit and put a clean hole thru both the brick and the liner.


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## Ralphie Boy (Dec 22, 2012)

Seasoned Oak said:


> Update: Well the 4" diamond blade on an angle grinder did the trick .Like a hot knife thru butter. You got to be very careful though,those angle grinders are hard to control and i did get hurt with one a few months ago. Probably the very best way would be to rent a 7" diamond hole saw bit and put a clean hole thru both the brick and the liner.


Nice work. I'm glad it worked out so well for you. The M-10 would have been more fun though!


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## ScotO (Dec 22, 2012)

Glad the diamond blade worked out for you, Randy.  I used one for around 7 hours last week when I cut all the pieces of stone to make stone registers for my fireplace chase.  Rotozip also makes a diamond burr bit that works fantastic for cutting stone, tile, quartz, marble, etc......I have one of those too.  They are pricey (I think the bit was 30-some bucks), but they are awesome for when you need to make an odd cut in masonry.  I may only use it a couple times in my life, but it's there when I need it.


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