Thanks for the replies. The 16mm was turned down from 18mm, and then down to 10 for the spigot, so I am fairly sure they are concentric. They are still on the stock, so I can clock them in the 4 jaw and just check.
The 10mm hole was drilled through the baseplate, and then bored out to 16mm without moving the mill table. My little SX1LP will not drill 16mm in steel, so I had to use the boring head.
Next time I will do as Jason suggests and bore out both holes. I will see if I can get the holes measured with the DTI on the mill, but I will need to centre (one of) the holes as a starting point. I was hoping someone had a neat trick before I start doing that.
It's not actually an issue as the 16mm is the location fit, but I would just like to see where I went wrong – this time!
Thanks again – the finger plate actually seems very useful.
Edited By Peter Cook 6 on 02/07/2023 11:12:04