Braking grease

[Bonefixer]

Just checking I’m understanding this right. 
 

When servicing an automatic watch I’ve learned to put grease onthe walls of the mainspring barrel. This is to allow the spring to slip a bit and prevent it from overwinding and breaking. Is this right?

Presumably if I were to use a very low viscosity oil, say 9010, this would prevent the mainspring from winding at all - it’d just slip round and round, storing no energy?

Have I got this right?

[Kalanag]

You might read the discussion in this interesting thread:

https://www.watchrepairtalk.com/topic/30176-braking-grease-a-myth

[VWatchie]

9 hours ago, Bonefixer said:

This is to allow the spring to slip a bit and prevent it from overwinding and breaking. Is this right?

Yes! You would think the reverse given the name. That's what I thought for a long time until I realised that the grease was there to facilitate the slipping of the spring. The spring wouldn't break, but other parts in the movement would be damaged, and it would cause re-banking.

Otherwise, I recommend @Kalanag's link and you can also search using this link:

https://www.google.com/search?q=site%3Awatchrepairtalk.com+braking+grease

Edited September 10, 2024 by VWatchie

[Bonefixer]

Thanks for the replies. My understanding now is it's there mainly to prevent wear. No grease and it would still slip, but the friction would damage the spring and barrel. 
 

With a light oil you'd perhaps get less power reserve as it would slip earlier. 
 

I use 8217. But I'm sure it'd be ok to use anything? 9504 for example?

[Kalanag]

1 hour ago, Bonefixer said:

I use 8217. But I'm sure it'd be ok to use anything? 9504 for example?

Based on the SDS the 9504 does not contain MoS2, Graphite or PTFE