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Are Doubler Roller Jewels shorter than Single Roller Jewels? "Click" to Login or Register 
posted
Recieved a Bunn 16s SN 5132293 21j 60HR Type 3.
The lower balance staff pivot was bent and the roller jewel was laying inside the pallet area.

During the repair I managed to loose the one jewel and feeler gauged it to a tight 54. The guage was tight enough that it was stuck and I had to wriggle it out. I located a 52 and put it in.

I think it is hitting the impulse pin. And everytime I reinstall the balance it is over banked when I pull it to inspect. I find the balance wheel turns in one direction and since it becomes over banked the opposite direction is just locked.

I am going to take a guess that the watch had another too long jewel which lead to the frustration I am having with it.

I looked at another roller table and SURE ENOUGH that jewel (DR Bunn Special) is SHORT!!!.

My question then is can I reheat the longer’s shellac and simply PUSH the jewel up through the top? Would that be a common practice whenever the shorter one is unavailable?

Is this DR roller jewel necessarily shorter than a single roller because of the additional space taken on the staff by the safety roller? This is quite unnerving.

This all sounds like it fits where the impulse pin gets shoved because the longer jewel is PROTRUDING through the pallet horn or perhaps the jewel does never enter the horn since it figures that the pallet RUNS AWAY after the slightest contact between the pin and jewel.

I think I will use the longer pin but make it effectively ‘shorter’, as a workaround. Am I committing Bunn Hari Kari and going to be tossed in the lake of FIRE if I do this ?

My Lamp!
 
Posts: 136 | Location: New York in the USA | Registered: September 23, 2018
posted
James it is fine to use a longer roller jewel as you mentioned and just slide it up far enough so that the safety table gets clearance and also make sure the roller jewel is going into the pallet slot to impulse. You can't block the crescent in the safety table with the roller jewel.

Rob
www.pocketwatchrepairs.net
 
Posts: 580 | Location: Kingsport, Tennessee in the USA | Registered: November 26, 2002
posted
Rob, Yepper. Safety intrusion! Oooops. Now I know what those short jewels are meant to do. I wonder if I tried to use a file or a dremel and shortened it? Or reheat and reposition. If it is tight it can be ground down and checked for being loose. I don’t have a clue how hard it is.

 
Posts: 136 | Location: New York in the USA | Registered: September 23, 2018
posted
Done City. I used the dremel tool and cleared the cresent in the safety table. ThankYou for the Help Sir.

 
Posts: 136 | Location: New York in the USA | Registered: September 23, 2018
posted
James,

If you used shellac for the roller jewel it is easy to reheat and reposition the roller jewel. I remove the hairspring before I put heat to the balance.

Rob
 
Posts: 580 | Location: Kingsport, Tennessee in the USA | Registered: November 26, 2002
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