Gear post knarled after broken screw removed

[tdfguy]

Hi All,

I am either trying to repair this pivot or obtain a new main plate.  I have not been able to find a main plate.  The movement is a Monpilier 60.  My question is, what is the name of the cutter that makes these holes?  I drill/reamer for the center hole?  Can I silver solder the hole and recut things the way I need it to be?

Thanks,

Don

[watchweasol]

Hi Don  I think the best approach is to re bush the hole and then droach it for the center vwheel shaft.  Carefully drill or brach the worn hole and press in a bush, either a blank bush or better still one with a hole slightly smaller than the diameter of the shaft to allow a tailored fit.

[nickelsilver]

This is a very tricky repair; typically the issue is wear on the outer diameter, are you dealing with that or stripped threads from the screw? Since this is over the hole for the stem pivot, there is very little material around it.

 

Once approach would be to bore it out, and press in a new threaded piece the correct outer diameter. It would require re-drilling the hole for the stem pivot, and careful fitting so that it doesn't budge when screwing in the screw. A solution is making a stepped tube, and an appropriate recess for the step on the movement side of the plate (just a little step, 0.1mm is enough). It's fiddly work.

 

My preferred method if there is wear on the outside, and if there is enough material between the inner and outer diameters of the post, is: in a faceplate, turn the outer diameter of the post down, leaving enough material that it can take a sleeve. Make sleeve from steel, harden, temper, install with Loctite 648. Often this is a solid post, no hole or thread, so it's less of a challenge.

Edited June 20, 2022 by nickelsilver

[tdfguy]

Hi All who responded,

How are these pivots made when the plates are being manufactured?  What type of tool bit is used?

[LittleWatchShop]

The real experts have responded with ideas, but I have yet another idea that might work.

Leave the current post in place and make a bushing to insert inside of it.  Tap that bushing with a smaller hole and make the appropriate screw.  Then make a tool with a hole of the correct outside diameter and use it to burnish the outside so that it is a smooth round post.  You will still need to drill a hole for the stem but you will have a guide.

This is a serious repair requiring a lathe and some skill.  Even though I am an amateur, I would try it since the plate, as is, is useless.

I would be interested to know of @nickelsilveror @watchweasolthinks this could work.

[watchweasol]

I think its possible, but the various ways this can be done require, the tools and the skills. But as mentioned as the plate is its scrap so its a case of choosing the method which suits your level and proceeding with caution.

[nickelsilver]

I know this doesn't help the OP, but I had to sleeve one of these externally yesterday so I snapped some pics. You can see the post is super worn, and it made setting very hard. I turned the post down in a faceplate, turned up the sleeve in beryllium copper, pressed it on, and bingo!

 

 

[watchweasol]

A very neat job from the professional with thr right tools and skill.  may one ask how long it took to complete.  a brilliant job.

[nickelsilver]

1 hour ago, watchweasol said:

A very neat job from the professional with thr right tools and skill.  may one ask how long it took to complete.  a brilliant job.

Thanks WW. Probably about 20 minutes start to finish- but I have a dedicated lathe for faceplate work with optical centering, and the (tiny) cutting tool I used there was ready to go. My small lathe is always ready to go, haha,  as I use it every day, usually multiple times, so the sleeve took no time. Probably spent as much time measuring as cutting/ installing.

 

This is for a maker that starts with a big R, and apparently this is such an issue that they supply some of their repair centers with a special setup for recutting the post and sleeves ready to fit. You'd think they'd just fit a hard steel sleeve there or something to begin with...

Edited June 23, 2022 by nickelsilver

[ifibrin]

15 minutes ago, nickelsilver said:

Thanks WW. Probably about 20 minutes start to finish- but I have a dedicated lathe for faceplate work with optical centering, and the (tiny) cutting tool I used there was ready to go. My small lathe is always ready to go, haha,  as I use it every day, usually multiple times, so the sleeve took no time. Probably spent as much time measuring as cutting/ installing.

 

This is for a maker that starts with a big R, and apparently this is such an issue that they supply some of their repair centers with a special setup for recutting the post and sleeves ready to fit. You'd think they'd just fit a hard steel sleeve there or something to begin with...

Wouldn’t it be easier to drill out the post on a lathe, then reinsert a new steel post into the hole? I assume that is how some of the posts on main plates are made anyway.

[nickelsilver]

2 minutes ago, ifibrin said:

Wouldn’t it be easier to drill out the post on a lathe, then reinsert a new steel post into the hole? I assume that is how some of the posts on main plates are made anyway.

On this one the material is too thin to reliably hold a new pressed in post.

[ifibrin]

Just now, nickelsilver said:

On this one the material is too thin to reliably hold a new pressed in post.

Oh you mean that the original post was originally machined out of the same brass block as the main plate? Meaning that the post was not inserted in, but is actually part of the entire main plate?

[JohnR725]

the title implies the damage was done when the screw was being removed?

just a reminder for people that are new here. If you break a steel screw off in a brass plate. Providing there is no other steel components in other words you have to remove everything. The steel screw can be dissolved out. Versus attempting to remove it other methods which can be destructive. I find often times people forget or don't realize there are other ways of getting screws out and dissolving works really really nicely.

 

 

3 minutes ago, ifibrin said:

Oh you mean that the original post was originally machined out of the same brass block as the main plate? Meaning that the post was not inserted in, but is actually part of the entire main plate?

yes all machined out of one piece of brass. Good for manufacturing point of view very bad from a repair point of view

[nickelsilver]

4 minutes ago, ifibrin said:

Oh you mean that the original post was originally machined out of the same brass block as the main plate? Meaning that the post was not inserted in, but is actually part of the entire main plate?

Yes, which is often (usually) the case.

[ifibrin]

4 minutes ago, JohnR725 said:

the title implies the damage was done when the screw was being removed?

just a reminder for people that are new here. If you break a steel screw off in a brass plate. Providing there is no other steel components in other words you have to remove everything. The steel screw can be dissolved out. Versus attempting to remove it other methods which can be destructive. I find often times people forget or don't realize there are other ways of getting screws out and dissolving works really really nicely.

 

 

Do mainplates generally have a number of steel posts, especially in the motion work or the keyless work? Wouldn’t this dissolve those steel posts as well?

[JohnR725]

12 minutes ago, ifibrin said:

Do mainplates generally have a number of steel posts, especially in the motion work or the keyless work? Wouldn’t this dissolve those steel posts as well?

generally the plates are made out of brass all brass.  everything that resembles a post is just machined in typically.