Reply To: Waltham rattle…

[tmac1956]

Bob and all:

Using Bob’s check list and David’s suggestions, I think I have isolated the problem, but I want to describe it as accurately as I can and pass my findings on to those here with more experience.

I took everything apart and examined the balance foot and top jewel pairs again under magnification. They are fine showing no cracks or oval shaped holes. I had already taken them out and examined them, cleaned and oiled them so I am confident that the jewels are intact. Next, I put a stump on my staking set, found the correct flat holed stake and put moderate pressure on foot and top jewels to ensure they were securely seated in the plate and balance cock, putting additional tightening on the screws just to be sure. No slop there.

I put the balance assembly into a truing caliper and examined the balance wheel. It was about as true in the flat and the round as I have seen yet. Additionally, the hairspring appears to be in good shape lying flat on the wheel with the over coil and hairspring stud in the proper location. The safety roller appears to be a replacement and looked to be seated squarely onto the balance cross arm/balance seat and seemed to be installed correctly. The safety jewel seems to be well secured and nicely perpendicular to the safety roller table. I then attached the hairspring back onto the balance cock making sure that the hairspring stud was fully engaged and that the hairspring was seated between the index pins.

So without any other components back in the watch, I replaced the top plate and the mainspring barrel plate (without the barrel) tightening them down securely. Next, I replaced the balance cock guiding the balance wheel/staff into the lower plate receptacle and seating it into the bottom jewel hole. I then seated the top pivot into the balance cock jewel and tightened the cock plate down. Using a camel hair brush I spun the balance wheel and examined the wheel/plate clearance. The wheel is running nicely flat above the plate with adequate clearance between the two. Additionally, the timing screws were free of the balance cock all around the balance wheel rotational arc. However, the balance still rattled.

So, I examined the movement between the plates while the wheel spun and it appeared that either the roller table or the jewel is banging the plate recess which holds the foot jewel. I just kept spinning the balance wheel until it finally locked. I then gently picked it up and visually determined that the safety roller had jammed against the plate with the roller jewel in the back position opposite the pallet fork side. This would be in the position under which the hairspring would be in a wound state.

Since the bottom jewel hole isn’t cracked and its hole is round, I can only assume one or more of the following problems exist:

1) The jewel hole is too big, allowing the balance staff to wobble enough to collide with the bottom plate.
2) Even though it visually appears to be seated correctly, the safety roller isn’t seated properly or is somehow out-of-round and/or off center to the balance staff.
3) The plate receptacle is not round and true, or the jewel seat isn’t perpendicular to the balance staff.

I suppose I should attempt to replace the bottom jewel pair first and if this doesn’t fix the problem, I should replace the safety roller.

OK. I appologize for being so verbose. Am I missing anything?

Thanks!
Tom