"Emergency Lathe", concept idea .....

[Endeavor]

Hello All;

In connection with the interesting current balance riveting discussion (https://www.watchrepairtalk.com/topic/28854-new-balance-staff-not-riveting-to-balance/#comment-243895 ), I like to bounce off my "one-off" or "emergency lathe" idea.

I too need to change out a balance staff, this time from a Valjoux 5 chronograph movement.

I've done successfully a balance staff change out before, but on hindsight I wasn't too happy with the way I did it and nearly screwed up the hole in balance-wheel.

Not having a lathe, I could knock the staff out using my staking tool or perhaps use Alum (potassium aluminum sulfate) to de-solve the balance-staff.

While polishing the screw-heads of a nearly finished Le Phare 114CVV chronograph pocket watch, the idea came to me to convert my screw-head polishing tool into a "one-off" or "emergency"-lathe to remove the balance staff rivet-rim.

As some of you may know, I made a variable-speed belt-drive for my Jacot tool;

 

Using the same setup with my screw-head polishing-tool give this;

 

With the handle-bearings well oiled, the motor drives the handle very nicely. The two "runners" in front of the tool can be adjusted in height and would double as a nice support for a cutter.

Now I know, there are some "problems", one of them being is that the handle is laying loose in the bearings and could potentially lift-up when the cutting forces are becoming too high. I discovered that, next to the weight of the handle, proper oiling seems to additionally "suck" the handle into the bearings. Also the positioning / angle of the bit will become critical.

But how much force is developed / needed when cutting a balance staff rivet-rim? Also nobody says that the rim has to be cut within 1/2 minute and of course the cutter has the be sharp.

To me there are another advantages, if this were to work for "light" lathe work.

I do already own the polishing-tool and the tool comes with a nice selection of chucks, suitable for nearly all watch balance-staff dimensions and other small items

and I do have already a nice variable-speed belt-drive for it.

Obviously I like this idea to succeed.

Any of you some suggestion on  how to improve on this idea?

 

 

 

[mikepilk]

Nice idea, but as you say, there are "problems". Being hardened steel, I assume a reasonable amount of force will be required.

How did you do it previously? I too don't have a lathe, and use the K&D tool to punch out staffs. I have never noticed any damage to the holes. As mentioned in the previous discussion, it depends on what the balance is made from. I recently changed the staff on a Longines. After removing the staff I examined the hole under the microscope and could see no marks at all.

But if I had a lathe ....

[Endeavor]

38 minutes ago, mikepilk said:

How did you do it previously?

I don't want to de-rail this thread, but I used my staking set.

38 minutes ago, mikepilk said:

Being hardened steel, I assume a reasonable amount of force will be required.

As said, nobody said that the rivet ring has to be cut within 1/2 minute. I was planning to cut in small increments. Even if I were to manage to weaken the rivet-ring, that would already be an improvement compared to banging the whole thing through the balance-wheel.

Edited March 6 by Endeavor

[RichardHarris123]

If the screw head polishing tool was raised above the drive the belt would be pulling down on the shaft, helping to keep it in place.  A plastic sheet could be cut, lightly greased and held against the shaft with elastic, a temporary crude bearing. 

I read a post where a soldering iron was used to anneal the staff. 

[Endeavor]

26 minutes ago, RichardHarris123 said:

I read a post where a soldering iron was used to anneal the staff. 

All those (small) things may help, thanks for the tip

26 minutes ago, RichardHarris123 said:

If the screw head polishing tool was raised above the drive the belt would be pulling down on the shaft, helping to keep it in place

That is going to be a bit problematic since the driving unit is light in weight and currently free standing. However, the front bearing of the polishing tool has a recess-groove and since the belt is pulling sideways, the rotating handle is a kind of "secured" sideways. Most likely, it's when the upwards force is higher than the "suction-force" of the oil, the weight of the rotating handle and the "locking-force" of the sideways pull in the groove, that the handle may become "unstable". But to my mind, to archive that force, compared to the size of the rivet-rim, the cutter has to really "dig-in"  ......

Edited March 6 by Endeavor

[VWatchie]

2 hours ago, Endeavor said:

Not having a lathe, I could knock the staff out using my staking tool

I think that's a really bad idea, but if that becomes your only option, perhaps several ultra-gentle taps with the hammer could save the day.

[Endeavor]

35 minutes ago, VWatchie said:

perhaps several ultra-gentle taps with the hammer could save the day

Thanks for the tip, and I knew that. As said, using the staking tool wasn't my preferred method, hence I'm seeking to improve upon that with my "emergency lathe" idea.

I don't want this thread to become an exchange of thoughts which way is the best, we have the other thread, referred to above, for that.

Instead I like members to come up with constructive idea's / recommendations / suggestions / tips etc to make my "emergency Lathe" concept work

 

[VWatchie]

43 minutes ago, Endeavor said:

I don't want this thread to become an exchange of thoughts which way is the best, we have the other thread, referred to above, for that.

Absolutely, I will respect that 100 per cent! 

44 minutes ago, Endeavor said:

Instead I like members to come up with constructive idea's / recommendations / suggestions / tips etc to make my "emergency Lathe" concept work

That would be fantastic and an inspiration, and I wish I could contribute.