Hello, all...
I'm about to start my first bushing job on a Hermle grandfather clock movement with a couple of problem areas that need rebushing. I've spent lots of time over the past few months reading everything I can on this forum about hand bushing, watching videos, etc. I've read Bangster's excellent post on hand bushing.
The general opinion seems to be divided between making a worn pivot hole symmetrical with a cutting broach, and making it symmetrical with a needle file. I have a spare Urgos grandfather clock movement I purchased cheaply from Ebay that I intend to practice hand bushing on, and I'm happy to try out both the needle file and cutting broach method (broach approach?).
The winding arbor pivot holes on this movement are particularly bad, one with about 0.7 - 0.8 mm of wear from a 3 mm pivot. I'm thinking that whichever method I end up trying, I need to find either a needle file or cutting broach with a 3 mm diameter somewhere on it for making the pivot symmetrical before broaching/reaming to size. My current plan is to find the 3mm point on the broach/file with my calipers, and mark it so I don't end up going larger than 3 mm when removing material on the unworn side of the hole.
What do you all think about needle file vs. broach, especially for wear from such a large pivot?
I'm about to start my first bushing job on a Hermle grandfather clock movement with a couple of problem areas that need rebushing. I've spent lots of time over the past few months reading everything I can on this forum about hand bushing, watching videos, etc. I've read Bangster's excellent post on hand bushing.
The general opinion seems to be divided between making a worn pivot hole symmetrical with a cutting broach, and making it symmetrical with a needle file. I have a spare Urgos grandfather clock movement I purchased cheaply from Ebay that I intend to practice hand bushing on, and I'm happy to try out both the needle file and cutting broach method (broach approach?).
The winding arbor pivot holes on this movement are particularly bad, one with about 0.7 - 0.8 mm of wear from a 3 mm pivot. I'm thinking that whichever method I end up trying, I need to find either a needle file or cutting broach with a 3 mm diameter somewhere on it for making the pivot symmetrical before broaching/reaming to size. My current plan is to find the 3mm point on the broach/file with my calipers, and mark it so I don't end up going larger than 3 mm when removing material on the unworn side of the hole.
What do you all think about needle file vs. broach, especially for wear from such a large pivot?