Hello Troy and Jack,

Thanks for posting that up Troy. I wasn't very clear with my answer, sorry. It's like a leather strop for a razor. A back lap will take away all the tiny imperfections, but you will still have to grind eventually. Sorry if I muddied the waters! And the bloke is deadset right about the bedknife buddies. Cheap and awesome from Reel Solutions in QLD.

And to belatedly answer your question, 120-180 should suffice. Most of the people I know who regularly back lap seem to use 120. You can use valve grinding paste in a pinch, but beware the clean up. It's not water based! Don't really recommend but it is an option if you're truly stuck.

Jack, where do you stand on relief grinding a domestic cylinder?

I don't collect mowers. I just require Multiple Mowing Solutions™.