Nightmare chimney job

[Arnold9801]

I’m looking for some advice regarding my chimney. I took a gas flexi liner out as we want to put a solid fuel burner there’s instead.

The problem I have is that I have to widen the vermiculite/cement mix in the chimney that was around the gas fleximliner to accommodate a new 6 inch liner. It isn’t about as hard as dry clay or a week cement mix, but nevertheless is a swine to cut. I’ve hired a 6 inch core cutter but it was not working. Furthermore the six inch flexi needs a 7 inch hole to allow a smooth decent down the chimney.

I’m going to see if I could adapt a bike sprocket by attaching it Tom a threaded bar and use this as a form of router to see if that will cut a 7 inch housing for the liner. I’m not confident henceforth coming on here for some advice please.

For your info, I have to cut down from the removed clay pot through four foot of chimney. From there down I still the original granite chimney which is large enough for the 7 inch liner.

 

[sunnybob]

Brute force?
club hammer and progressively longer chisels?
It might be easier to build a new wider collar than boring out the old one.

 

[Sheffield Tony]

Brute force and a 6' metal bar might be as easy as anything. A set of those dirt cheap 1m long sds drills, possibly used as a chisel with roto stop on ?

 

[Arnold9801]

I have used various length crow bars with the chisel, spike and claw. The problem I’m having with these is that the neck at the top of the chimney is so narrow that you have to go in almost vertical with each blow resulting in the cutting edge skimming off the sides removing next to nothing.

 

[sunnybob]

remove the clay chimney pot.
Sometimes its much easier to go back a couple steps and start again.

 

[Sheffield Tony]

I had kind of assumed you'd do that, so you can get behind the vermicrete and lever the waste inwards.