Repivoting escape wheel

SuffolkM

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Hi guys

I've got a Japy Freres French clock movement in which stopped, and the reason I've discovered is that the pivot on the escape wheel is broken (a little stub left). The arbor is 1.1mm across before the shoulder, and judging from the stub the pivot might be around 0.4mm.

I can get carbide drill bits this small, and with a micro-chuck I think I can hold them in the tailstock. I'm going to do some tests on a few scraps as I have not worked on anything remotely approaching this level of delicacy before (generally I'm looking at longcase clock parts - giants, by comparison). Can anyone advise on tips, tricks or generally the best way to do this? I'm concerned about concentricity, how to spot the centre of such a small arbor, and how to support the part in the chuck - I imagine even the slightest wobble is going to break the drill bit?

Many thanks,
Michael
 

wow

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Michael, those Frenchies are made of such hard, brittle steel, I find annealing the end first a necessity. Just heat about 1/4 inch red hot and let it air cool. I use a collet holder in my Sherline to hold the arbor and a chuck in the tailstock. A very small graver usually works to make a center dimple. It’s a great idea to practice on a few that size first.
 
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Vernon

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Hi WOW,

Having not done this on a French clock, it seems that solder was used to hold things in place like wheels. Do you think maybe a wet rag covering the wheel and arbor as a heat sink wise?
 

wow

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Hi WOW,

Having not done this on a French clock, it seems that solder was used to hold things in place like wheels. Do you think maybe a wet rag covering the wheel and arbor as a heat sink wise?
I have not encountered solder on them. Pressed and staked joints are usual. It would not hurt anything to keep them cool, though. A good mini torch will allow you to get just the end of the arbor red hot without much heat elsewhere.
 

SuffolkM

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Thanks for the tip, Will - good advice indeed on the annealing. Do you have any suggestions on a suitable turning speed for a job at this small scale? I'm certainly going to do a number of test runs (and will report any disasters back for the benefit of anyone else interested!) but keen not to trash a load of drill bits. I'm slightly concerned about how to support the wheel in the chuck end, too, as it may be gripped from the pinion. Perhaps I am over-thinking this.
 

wow

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Once you mount it and run at a slow speed, you should be able to detect any wobble. That’s why I like using collets rather than a chuck. They give a secure mount every time. The speed is a “your choice” thing. The kind of drill you use and it’s sharpness are determining factors for the speed.
 

shutterbug

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If those wheels are indeed soldered to the arbor, I think it would be wise to send the job out to a pro. There aren't too many like that out there, but if the solder melts you have major issues. Maybe you could post a few pics of the wheels so we can determine what you have before you start on it.
 

SuffolkM

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Thanks Shutterbug. The part I have doesn't have any solder - Vernon's might? Mine is just staked on.
 

Jim DuBois

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On many French clocks, brass wheel collets are held onto the shaft with solder. You will need to heat sink the escape wheel and its brass collet to keep the solder from melting and providing you with real problems. Also, some of the steel used in these clocks will air harden to some extent. So, just annealing it and rapidly removing the heat may not yield as soft of steel as one might want. Repivioting these can be more art than science. They do get easier over time but I would not describe it as an easy job for an inexperienced person. I would rather do a half dozen tower clock repivot jobs than one micro-miniature French clock repivot job. But, folks who have done a lot of them find them much easier, or so I have been told.
 
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R. Croswell

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Be absolutely sure that the hub onto which the wheel is staked isn't in fact soldered to the arbor, as others have suggested. It isn't simply soldered to keep it in place, but to keep it centered. The hole is usually significantly larger than the arbor and filled with solder with everything centered so it isn't a simple matter to just resolder. It can be a real mess..........don't ask how I know this.:whistle:
 

wow

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Shutt, Jim and RC, thanks for letting me know about the solder. I have done only a few of the Frenchies and never encountered any with solder. I’ll definitely watch for it in the future. I haven’t broken a French pivot in years but have had to deal with several that came to me broken. When I first started many years ago, I used those old “ad-on”pivots where you solder them on to the end. Those are a mess. Hardly ever provide a good repair.
Practice practice practice first, Michael.
 

Jerry Kieffer

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Hi guys

I've got a Japy Freres French clock movement in which stopped, and the reason I've discovered is that the pivot on the escape wheel is broken (a little stub left). The arbor is 1.1mm across before the shoulder, and judging from the stub the pivot might be around 0.4mm.

I can get carbide drill bits this small, and with a micro-chuck I think I can hold them in the tailstock. I'm going to do some tests on a few scraps as I have not worked on anything remotely approaching this level of delicacy before (generally I'm looking at longcase clock parts - giants, by comparison). Can anyone advise on tips, tricks or generally the best way to do this? I'm concerned about concentricity, how to spot the centre of such a small arbor, and how to support the part in the chuck - I imagine even the slightest wobble is going to break the drill bit?

Many thanks,
Michael
Michael
As others have mentioned, it is almost certain you will need to anneal the section of arbor to be drilled. My personal copper devise for doing this is shown in the first attached photo. In the photo a watch wheel is shown with only the arbor section to be drilled making contact with the devise at the blue arrow. The leg of the devise is heated from the bottom red arrow to the top red arrow and then over the top until the drilled section is red hot. It is then left for about ten minutes to slowly cool allowing the arbor to anneal. Heat is applied using a Micro A/O torch on the surface per the black arrow. This procedure can be used with soldered wheels as the heat is contained to the area that makes contact with the devise and the wheels rarely go much higher than room temperature.

While I can make suggestions for accurately drilling for repivoting, I would need to know what Lathe and accessories you have as each machine requires slightly different manipulation. My one suggestion in general, would be to avoid the use of carbide circuit board drills. While they are certainly capable of cutting steel, they are not designed for steel and risk of breakage is much greater than drills designed for this specific type of application.

Jerry Kieffer fullsizeoutput_791.jpeg
 

SuffolkM

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Thank you Jerry, and others, for being so exceptionally helpful towards me with this repair problem. Heaven only knows what I would do without you!

I've attached a few more photos, including some captures from the digital microscope, which I think actually *do* show the wheel has been floated onto solder - so the tips about how to avoid heading the escape wheel and collet are all noted.

Jerry, my lathe is a mini-lathe (SC2-300, the usual affair). I think my first gap here is a 4-jaw chuck for the headstock. I have the basic accessories, a 3-jaw chuck, a travelling steady, a fixed steady, and a micro-drill (which fits to the MT2 tailstock), a small variety of gravers, plus a burnishing stick. I am not averse to taking my time and getting any helpful tools in for this job. I don't think I can use collets on the headstock due to the pinion, but it's been suggested that you can clamp onto the collet on the pinion side, potentially after turning it to true for the arbor, which seems pretty smart. That would mean the escape wheel is right up against the chuck.

I've got plenty of small carbide drill bits and have been thinking perhaps they could be run very close to the jaws of the drill to reduce play. My big worry is that if this set up is not concentric, there will not be a second chance.

Michael

Screenshot 2020-12-14 at 19.04.56.png IMG_7609.jpeg Screenshot 2020-12-14 at 19.04.27.png
 

Jim DuBois

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I can't say every French clock has the collets soldered on the arbors, but I will say the majority that I have observed have been. And, if you melt the solder there is a pretty good likelihood it will cool and run off-center. As RC commented above, don't ask me how I know that. There are a couple of possible techniques to hold your escape wheel well and keep it protected while also running the operation on center. One method is to turn a larger than your escape wheel diameter block of wood or aluminum in your lathe and drill a through-hole for the pinion and wheel collet to slip through. Then bore a recess the diameter of the escape wheel and as deep as the thickness of the wheel. The escape wheel can then be superglued in the recess, and the work can then be done to repivot, gently. When the arbor is drilled and a new pivot fitted the escape wheel can be treated with acetone or like solvent to free it from the block, or if you select an aluminum holder, a bit of heat will free it from the superglue. This can all be done in less time than it takes me to write about it.

Depending on your lathe, its size, and if you have collets, the pinion can be grasped in a collet and the front portion of the arbor can be supported in a steady rest to drill and repivot. If you only have a 3 jaw then you can do about the same thing by placing a piece of aluminum or brass in the chuck, drill a hole in the material the same size as the diameter of the pinion, slip it in, and super glue it. Then support the outer end with a steady rest as before. Face off the arbor, center a small v in the face, drill it, place in the new pivot. Jerry K's use of a tiny boring bit is a great way to center the v in the arbor, but difficult to execute in something as small as your arbor. But these approaches do work, I have used them on multiple occasions, and they are not as cumbersome as they may sound.

Jerry K has also recommended if you do use a carbide circuit board drill that you break it off the shaft and only use the twist portion grasp in a collet to drill. I have found once again his advice to work extremely well. I prefer not to have a carbide tip broken off in an arbor I am trying to repivot, and Jerry's method has helped me considerably.

And for those who think we should never use superglue in our work, you can substitute hot shellac for it. We have 200-year-old repair papers that recommend that. Superglue is just easier and holds better.

By the way, nice photo details!
 
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JimmyOz

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Here is a thread that I had input into and caught a bit of flack for the way I did it on a French fly and therefore went about doing it the 'right' way on a junk pile French escapment wheel. Not to say it is the right way, however it worked well.
 

Jerry Kieffer

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Thank you Jerry, and others, for being so exceptionally helpful towards me with this repair problem. Heaven only knows what I would do without you!

I've attached a few more photos, including some captures from the digital microscope, which I think actually *do* show the wheel has been floated onto solder - so the tips about how to avoid heading the escape wheel and collet are all noted.

Jerry, my lathe is a mini-lathe (SC2-300, the usual affair). I think my first gap here is a 4-jaw chuck for the headstock. I have the basic accessories, a 3-jaw chuck, a travelling steady, a fixed steady, and a micro-drill (which fits to the MT2 tailstock), a small variety of gravers, plus a burnishing stick. I am not averse to taking my time and getting any helpful tools in for this job. I don't think I can use collets on the headstock due to the pinion, but it's been suggested that you can clamp onto the collet on the pinion side, potentially after turning it to true for the arbor, which seems pretty smart. That would mean the escape wheel is right up against the chuck.

I've got plenty of small carbide drill bits and have been thinking perhaps they could be run very close to the jaws of the drill to reduce play. My big worry is that if this set up is not concentric, there will not be a second chance.

Michael

View attachment 627276 View attachment 627277 View attachment 627278

Micheal

By Mini Lathe SC2 I am making the assumption we are speaking of the Chinese 7 X 10-12-14 or 16 lathe.
The first attached photo is of my current and the latest version of this Lathe that replaced my last one of about 10 years. As a note of interest to some, I have been told that the quality had improved in recent years. However, it has not been the case with this Lathe.

Unfortunately, this Lathe and its accessories has not been designed to do the size and type of work required for your project. I can bore you with the details, but I will make a very long story short. If I were forced to do this job on my Lathe in the photo, It would take at least a week to make major modifications in accurate work holding capabilities, alignment and drilling sensitivity. In the end, I may or may not have a shot at success.

If this is your only option, I would suggest that you farm this out and save yourself a lot of grief and heartache. It will be far less expensive and in the mean time you can explore options for this type of work in the future.

Jerry Kieffer



fullsizeoutput_792.jpeg
 

howtorepairpendulumclocks

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Hi guys

I've got a Japy Freres French clock movement in which stopped, and the reason I've discovered is that the pivot on the escape wheel is broken (a little stub left). The arbor is 1.1mm across before the shoulder, and judging from the stub the pivot might be around 0.4mm.

I can get carbide drill bits this small, and with a micro-chuck I think I can hold them in the tailstock. I'm going to do some tests on a few scraps as I have not worked on anything remotely approaching this level of delicacy before (generally I'm looking at longcase clock parts - giants, by comparison). Can anyone advise on tips, tricks or generally the best way to do this? I'm concerned about concentricity, how to spot the centre of such a small arbor, and how to support the part in the chuck - I imagine even the slightest wobble is going to break the drill bit?

Many thanks,
Michael

Sorry to jump in when the thread is well developed.

Yes the collets are soft-soldered. You do not need to heat the arbor to red, especially if using carbide. You may actually find it easier if the steel is hard as it will not grab as much. Yes, temper to blue with a spirit lamp and protect the collet with damp rag or jeweller's cool paste. Lubricate the drill with spit. As always, work-holding is the most difficult thing. You really ned a Jacot plate (plate with a chamfered hole in it) to hold the end of the arbor being drilled. The best way to find the centre is with a very sharp graver or better, the shank of a broken tungsten drill shank ground to a triangular point. Yes, do not start drilling until you are certain to have found the centre. If the worst comes to the worst and the hole isn't quite concentric, you can alway fit an oversized stepped pivot and turn to diameter but much 'easier' to get the centre in the first place. One of the biggest problems drilling with tungsten is the lack of control on a lathe with an electric motor. By the time the drill grabs, it is broken. If you can find/borrow one, a watchmakers lathe with hand-wheel is the way to go. Also, you might try with a spade drill (steel). There's a link here to making one
and "Watchmaking" by Daniels has lots on this subject. Basically with hardened steels, you need to drill dead slow and lubricate with spit. Experiment first on a piece of blued pivot steel that has been let down.
 
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SuffolkM

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Hi gents,

I've been doing some tests, starting with larger pivots and moving down in size. The drilling is not a problem, but concentricity is the blocker. After turning the collet on the pinion side true, I've been able to drill central holes, but not down to these sizes. Basically, as has been suggested, the tolerance is too fine for my setup (a microdrill with a feed-in spring, which is a few too many items in the tailstock after adapting to MT2). I'm still staying well away from the actual piece, but have not given up yet! It's interesting exploring the world of miniature, and I am now looking into how to get the drill bit held better. I suspect this is still not going to work, but hey, it's the weekend...worth a little venturing...!

Michael
 

howtorepairpendulumclocks

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:=) Probably best hold the drill by hand. Either in a small piece of wooden dowel or if TC, just hold the shank. When you buy a new TC bit, it usually has a piece of plastic pipe protecting the drill. Reverse this so it is on the shank end... makes a good holder.
 

SuffolkM

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Success! I completed a few test pieces (right down to 0.2mm holes) using just the keyless chuck instead of the microdrill, feeding in from the tailstock. I then decided it was time to be brave and go for it. I started by turning the collet true, so I could turn the escape wheel without any wobble.

I then tempered the pivot end after placing the piece under water, using a micro gas torch. I blued it, cooled slowly, and checked everything else was untouched. To hold the piece in the water I bent a hook out of a long brass taper pin.

On the lathe, I put the drill bit in with a tiny amount protruding from the chuck - probably less than a millimetre. This eliminated all the wobbles, and allowed me to press into the arbor tip to get a centre I could believe in. Edit: I tried this approach to make a centre, as I found I could not spot one with a graver accurately enough (needed to prep a graver with a very sharp point for this and I used the drill more or less to form a crater - not ideal). After that I broke it, and swapped to a new bit. This time I found I didn't need to be so careful, having obtained a centre, and just treated it more or less as a 'standard' job. You can imagine my relief to see some chips coming out. I took it really, really slowly (lots of clearing off the part and checking) but found I got best results running the lathe at a pretty normal speed, not slow. I used oil to keep the cut going properly.

As a I test I fitted the entire length of blued pivot wire, which bound with the hole perfectly - nice. So I shortened it, burnished and then rebushed the front plate of the clock to match.

I'm not taking a victory lap yet, because I have yet to reassemble the clock, but the repivoting at least is done. I will admit, this feels like a rite of passage. Once again thank you so much for helping me out. You can imagine that the annealing, if I'd thought of it, would definitely have melted the solder had it not been pointed out at a very early stage on this thread...;)

Cheers all!

Michael

IMG_7616.jpeg IMG_7617.jpeg IMG_7619.jpeg IMG_7621.jpeg
 
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wow

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Great job, Michael. I have learned a lot in this thread. I like your water/annealing idea. I also learned about the soldered French wheels. I will remember that the next time I repivot one.
Will
 
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