I prefer this sort of edge finder, although I must admit I've not tried the "wobbler" sort jamesgates1000 mentions. I'm starting to sound like a shill for Arc Euro but Cromwell don't seem to sell them and this came to hand. https://www.arceurotrade.co.uk/Catal...l-Edge-Finders

Forget where I got mine but it's 10mm shank and 4mmm tip, looking like their "Type C".

Have to admit I didn't know how to use it until I found one of these dummy guides on YT. Then it started to make sense and I realised how sensitive some of these tools can be.