Seiko 7006 post for reduction wheel with a groove?

[PeterS]

I’ve inspected the movement (Seiko 7006) and found that the post for the reduction wheel, the one with teeth for the pawl leaver has a machined groove in it.
I don’t quite understand the reason behind it and therefore unsure what to lubricate it with. The reduction wheel itself has some grey inside it so I’m guessing it was lubricated with the S4 graphite grease.
Does anyone know the reason why Seiko machined a groove in the post?

 

[jdm]

2 hours ago, PeterS said:

I don’t quite understand the reason behind it and therefore unsure what to lubricate it with. 

The reduction wheel moves slowly and it is not under much pressure, so whatever thick oil (graphite or not) will work fine. 

Some minor design details like this are not very important. You can find that the same manufacturer changes them in between versions or generations and even give different oiling instruction in their various service sheets.

[PeterS]

10 hours ago, jdm said:

The reduction wheel moves slowly and it is not under much pressure, so whatever thick oil (graphite or not) will work fine.

That’s what I thought, the S4, 9501, D5, anything like that should be fine.
It just puzzles me why they machined the groove there. It’s extra cost to the manufacturing so they must have had a good reason for it.
I was thinking whether it’s there as an ‘oil groove’, like an oil sink but that doesn’t make much sense. If not oiled properly and too much D5, or any other suitable oil ends up in the groove, that could potentially leak out and spread where it shouldn’t be. Putting grease in it, that wouldn’t go anywhere so it wouldn’t serve much purpose either.
Perhaps to reduce the friction? I really don’t know, I can’t think of anything rational.
I suppose it’s not that important, it will work just fine if I put some grease on it but if anyone knows the reason behind it, do let me know.

Edited July 3, 2022 by PeterS