How to remove this c1921 Bulova balance from its cock?

[mbwatch]

On 12/28/2024 at 3:08 AM, GPrideaux said:

Thank you, yes the spring is pinned to the stud. I'm optimistic I won't have to unpin/repin it. The stud is friction fit to the cock and I have been able to push it out using my staking set.

@GPrideaux I remembered your thread as I am also faced with a pressed in hairspring stud on a very low quality Desa 420 pin lever. Do you remember what stump you used on the staking set to support the balance cock for this? I can't work out the geometry of holding it up without pinching the hairspring underneath. I have a few different slotted stumps which were originally for roller tables I think, and one with a deep V shaped slot. But I can't figure out where the balance wheel and hairspring will dangle while the cock is positioned over a stump.

On mine, it feels very firmly pressed in and I am hesitant to go through with removing it knowing it's going to be hard to put back in. But I do want an opportunity to clean the pivot and oil this properly even if it's a 1 jewel junk movement.

[SwissSeiko]

9 minutes ago, mbwatch said:

@GPrideaux I remembered your thread as I am also faced with a pressed in hairspring stud on a very low quality Desa 420 pin lever. Do you remember what stump you used on the staking set to support the balance cock for this? I can't work out the geometry of holding it up without pinching the hairspring underneath. I have a few different slotted stumps which were originally for roller tables I think, and one with a deep V shaped slot. But I can't figure out where the balance wheel and hairspring will dangle while the cock is positioned over a stump.

On mine, it feels very firmly pressed in and I am hesitant to go through with removing it knowing it's going to be hard to put back in. But I do want an opportunity to clean the pivot and oil this properly even if it's a 1 jewel junk movement.

I would place the balance complete on a balance tack, and remove the balance wheel. Is the hairspring not held on the stud with a taper pin? Id try to leave this stud in, as setting it back to its original height might prove difficult.

[graemeW]

I've removed the taper pin to release the hair spring on the watch in working on maybe 10 times in the last week or so. Been using the same pin to re fit.

First time was a bit nerve wracking, but it's super easy now. I'd rather do that than mess with the stud. I use one pair of tweezers to press down on the cock to stabilise it, then just press it out a little and then pull from the wide end. No need for anything other than normal tweezers in my opinion.

[mbwatch]

6 hours ago, SwissSeiko said:

s the hairspring not held on the stud with a taper pin? Id try to leave this stud in, as setting it back to its original height might prove difficult.

Hahaha nope. It is glued into the stud!

[GPrideaux]

From memory I positioned an ordinary round stump off centre so that the punch came down beside it, then rested the edge of the stud carrier on the stump, holding the rest of the cock level and with the balance resting on the table of the staking tool while I brought the stake down and pushed out the pin. It was a bit of a juggle and a third hand would have been useful, but it came out really quite easily and similarly went back in without difficulty. (I know others prefer to remove the pin ... I haven't done that as yet.)

[mbwatch]

2 minutes ago, GPrideaux said:

but it came out really quite easily

Okay thanks. I did some pushing on mine last night and it is very firmly friction fit. I am afraid I might even need to use my jeweling press.

[mbwatch]

On 1/30/2025 at 4:55 PM, mbwatch said:

Hahaha nope. It is glued into the stud!

Ultimately I pushed out that stud. The watch was assembled and running at 300° even with an improperly oiled upper balance jewel, but with terrible beat error >5.0. I had to remove the stud to fix the hairspring I messed up trying to turn the collet from a balance tack.

I rigged it up in a V groove stump and was able to push it out with a balance staff removal punch. It was really firmly pressed in. I ran a smoothing broach through to make it easier to reinstall, pushed it back in and got it into beat. Now running again but not at 300 anymore since I didn't get the hairspring perfect.

One star review for the Desa 420 caliber with 1 jewel, no movable stud carrier, hairspring glued into a friction fit stud