I'm trying to take apart my latest addition but am stuck with removal of the ratchet and transmission wheels. Screws are very tight and I wonder if there is a way of telling whether they are left or right hand thread. If LH how do I stop the ratchet wheel from turning the movement?
Any tips and advice, as ever greatly appreciated

Thanks Lindell

I have let down the mainspring as you advise, the screws in question are approx 4mm dia, if LH thread how can stop the mvmnt spinning when trying to undo the screw, expected the transmission wheel to LH but not the ratchet wheel (barrel). Have attached a couple of 'dodgy' photos which I trust help, the watch is not signed anywhere that I've seen and there is no mvmnt No. But it has gold plated plates and screws regulator etc are very well finished
Thanks again for your help

Best wishes

2nd photo

Terry,

To add a little more to what Lindel has mentioned about letting down the spring, I usually crack these screws on Swiss movements Before letting down the spring - and on an almost fully wound watch - it helps keep the wheels locked.
Once cracked loose, then let down the spring, remove the stem and take the movement out of the case.

The ratchet wheel is likely to be RH and the transmission wheel a LH thread, and untightening either will lock the wheel against the click when unfastening.

Tightening both the transmission and ratchet wheels will consequently also start to wind the spring and add a bit of pre-load. I usually find that some pressure from the thumb is sufficient to hold the wheel anyway to nip the screw - avoid the temptation to jam the wheels with a screwdriver!.

Some later Swiss watches (mainly wrist)have a double slot milled into the LH threaded screw as a means of identifying which is which.
These screws on 'pockets' can differ though, so the rule is, try both ways with care!
They are meaty beasts as a rule, so you're more likely to chip a blade than break a screw if you go the wrong way first time!

When you take the movement out of the case, I would also strongly recommend taking off the balance before you do anything else - there's then less likelyhood of busting the staff or bending the balance rim from accidental pressure by a thumb catching it when handling the movement!

John

Many thanks John

Now you have explained it, makes consumate sense, will take your advice but have decided to invest in a 3mm driver as I have already busted a couple of 2.5's so when it arrives I will SLOWLY try and remove the subject screws
It is fantastic to have access to such experience and knowledge
my thanks again to you sir

Any time Terry, we're all here to help.

If you can, do get hold of some drivers that are the full width of the screw head, and make sure they locate well into the slot - those things can be Really tight!
On more than a few occasions, I've had the heads actually split in half getting them off they were so tight - and finding new screws for Swiss watches is not a fun place to be!.

John

Thanks John, I truly appreciate your sound advice, 3mm Bergeon has arrived, both trans and ratchet wheels off (both were LH thread),everything dismantled and currently soaking in napthene

Kind regards

Great news Terry, pleased to hear no screw heads broke off!

Must confess, the double 'left handers' is a new one on me, but not surprising all to be truthful!

You'll have to post some pic's of the finished article for us!

best regards

John