Vivien LEGER wrote:

i was expecting to plow ‘from both side’

My inclination is to always work from a single reference surface or edge whenever possible. There is almost always a small discrepancy between the “parallel” faces and always a slight amount of error in getting on center. So, it takes a great deal of fiddling about to get these things perfect. If you must, you must, but in this case a chisel solves the problem and saves a great deal of time. This is an example of what I call, “don’t waste time by using machine methods with hand tools.” Take advantage of their speed. You see, even though it takes a great deal of effort to land exactly on center so that you can come from both sides, it takes very little effort to get close enough to center that the eye _sees_ the detail as being on center. You may not even have to measure at all. On the other hand, if you flip around and come from the other side, the two grooves give a reference for each other and make discrepancies stand out. “Oh, I’ll just reset my grooving plane fence….” Yes, you could do that, but it is, again, another step and you want the grooves to match up all the way around. So, it is best to leave it set and work off of a common surface all the way around.

You mentioned making a transition to hand tools, so I’m offering this bit of philosophy in case it helps. In my opinion, hand tools require a different way of thinking in order to really reap their benefits.