I just completed my first staff replacement on a Hamilton 910. With only the pallet and balance installed and gentle hand motion the roller jumps out of the fork. It takes a few seconds for this to happen but it will not stay in place. Any suggestions? Thanks..Paul

One of the first things that you might want to check is the end play of the staff. I am assuming that you have the movement stripped and only the balance wheel and balance cock installed for the end play to be checked. Very simply take hold of the balance wheel with 3c or 5 tweezers and try moving it in between the pivots. There should only be a small movement anything in excess of very small will allow the roller to become sloppy in the forks particularly in the face up position.Hamilton 910's had a variety of different balance staff's and finding the right one can sometimes be a problem. I hope I haven't confused you with the explanation it is much easier to perform than to explain.
Good luck, Regards, John

Paul, There are three possible reasons I know of that would cause this;
1. The roller jewel "loosened" and has pushed up too far through the roller.
2. The Roller Jewel is broken.
3. There is a pivot issue (broke or bent) with the Pallet allowing the pallet fork to sometimes "miss" the jewel.

As I recall the 910 movement is a double roller which makes it very hard for the third option to happen.

John: Everything to my eye seemed ok with the shaking. I believe i have found the problem.

Dave: You hit it. This is a double roller with the safety roller missing. And i felt great just getting the staff in without breaking or bending anything. Back to the bench for more teardown.

Thanks to all. Paul

any tutorials on replacing a staff? I already have a good tutorial on removal, but is replacing the staff a difficult process? I have several 18 s Elgins of good quality, and the "only" problem with each is a broken pivot at the ends of staffs.

The best way is some hands-on help from a cooperative watchmaker, patience and a good staking set.

You might also wish to check out two books on watchrepairing. "Practical Watch Repairing" by Donald deCarle and "The Watchrepairer's Manual" by Henry B. Fried. These books not only will guide you through staff replacement but cover a whole range of topics on watch repair and will provide you with a reference for the "next" time you have a broken staff. It is very difficult to find a watchmaker these days let alone one who is willing to take on an apprentice.
Regards, John

There is one person in my area that donated a wonderfull book. Joseph A Bulova, School of Watchmaking. Training units. Very comprehensive detailed explanation on all aspects of balance wheel, staff work, hairspring work. Great book.

Paul

Thank you all! I am looking forward to getting more and more experience in the area.