Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.
We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.
We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
After removing the knock-out, the rough edges should be filed down with a coarse metal, half-round file or gently with a small grinder until the adapter fits snugly but easily. I used a file to take down the high points on ours and the adapter was fitting in about 15 minutes.
If I remember right, some ridge was left, but don't hold me to that. It was several years ago when I did this. Put the adapter inline with the knockout hole and then take a pencil or ink marker and draw a line around the edge of the adapter. That will guide you. The cast iron is fairly soft and filed pretty quickly once I got into it. A grinder or Dremel tool should also work, but don't get too aggressive.