Following the last post about this, it didn’t turn out to be as easy as I thought it would be to drill through the enamel flu pipe! I had the right metal drill bits but they just made no impression in the metal surface. It didn’t help that I was drilling from the side and couldn’t get a lot of force behind the drill but there was no way I could get the holes in it.
So, thanks to living in an area with mixed uses and a variety of services, I managed to get the holes drilled by the metal fabricator and railing manufacturer just up the road. I cycled up there thinking i”d also have to then go to a different place but the guys there were very helpful and said it was no problem to do two quick holes. It literally took him 3 minutes and no charge.
It was fairly easy to then get the damper fitted into the pipe then fit the pipe back into the liner, screw the register plate back up then fire cement the pipe back in.
The damper has made a real difference to how quickly the wood burns and also to the amount of heat coming out. The burn rate isn’t quite as low as i’d hoped but much better than before. A damper with fewer holes could be an idea and I’m thinking about fixing stove fire rope to the damper to further limit the air flow but so far it’s done the job.