Watchmaking tolerances

[AGIreland]

Hi, can any one tell me or point me in the right direction on where I can find information on allowable tolerances in watchmaking.
Eg. What are the min/max tolerance on watch plate jewel holes, min/max enter distance between a wheel and pinion. Any help on this would be greatly appreciated.

 

[Dave Coatsworth]

I am going to move this post to Watch Repair. I think it might do better there.

 

[DeweyC]

Hi, can any one tell me or point me in the right direction on where I can find information on allowable tolerances in watchmaking.
Eg. What are the min/max tolerance on watch plate jewel holes, min/max enter distance between a wheel and pinion. Any help on this would be greatly appreciated.

INFORMATION....kind a.

Pick a Hamilton watch and ask for the production sheets from the Library. I know they are available for the M21.

Modern day, it depends on the position in the train. escapement parts are held to .05mm endshake. Train wheels can be .10 mm. The tighter the endshakes, the less trouble with shifting parts in timing. Jewels are generally 1 size over the pivot diameter.

But production tolerances? The Ham process drawings are the only source I know. Train hole distances today? I would suspect they are held to 5 microns or so.

 

[Dave Coatsworth]

There was some difference among the American manufacturers regarding balance staff pivots and balance jewels. For the most part, the convention is one hundredeth of a millimeter difference. (e.g., a .12mm balance pivot would require a .13mm balance hole jewel.) Illinois and Hamilton, however, provided jewels in 'half sizes'. Therefore a .12mm balance pivot would require a .125 balance hole jewel.

 

[AGIreland]

Hi,
Thanks for the reply’s and info. The reason I ask is I’m reading daniels watchmaking book. In the book he uses a devoting tool, I was just wondering g how accurate this method of marking out really is and what would the allowable tolerance would be. And how accurate would it be in say laying out a watch movement like a 6497.

 

[AGIreland]

INFORMATION....kind a.

Pick a Hamilton watch and ask for the production sheets from the Library. I know they are available for the M21.

Modern day, it depends on the position in the train. escapement parts are held to .05mm endshake. Train wheels can be .10 mm. The tighter the endshakes, the less trouble with shifting parts in timing. Jewels are generally 1 size over the pivot diameter.

But production tolerances? The Ham process drawings are the only source I know. Train hole distances today? I would suspect they are held to 5 microns or so.

How do I request a production sheet, I tried doing a search in the library

 

[gmorse]

Hi AG,

In the book he uses a devoting tool,

Depthing tool?

A properly constructed depthing tool allows the optimum engagement between a specific wheel and pinion pair to be arrived at, not necessarily something that can be done simply by precise planting of the mobiles by measurements from a drawing.

Regards,

Graham

 

[AGIreland]

Hi AG,

Depthing tool?

A properly constructed depthing tool allows the optimum engagement between a specific wheel and pinion pair to be arrived at, not necessarily something that can be done simply by precise planting of the mobiles by measurements from a drawing.

Regards,

Graham

Sorry yes ment depthing tool. After you scribe the makes with the demoting tool, you then mark for the holes, how accurate would you be marking and then drilling the holes. Just wondering what the allowable tolerance would be when laying out the holes with a depthing tool.

 

[Jerry Kieffer]

Sorry yes ment depthing tool. After you scribe the makes with the demoting tool, you then mark for the holes, how accurate would you be marking and then drilling the holes. Just wondering what the allowable tolerance would be when laying out the holes with a depthing tool.

Proper depthing is based on tooth profiles that can even contain variations using the same cutter depending on how they are setup/utilized. While theoretical depthing measurement may be provided someplace, only actual test mating of a wheel/pinion will provide proven friction free operation as suggested by Graham. In a production movement, an initial prototype movement was perfected often in part through trial and error. From that point, the production movements are copied to a accuracy level that allows interchangeable parts without individual fitting of each part.
The exception may be the most expensive movements where hand work is required to meet exacting requirements.

Personally, when constructing a horological movement or other functional micro assembly, I seldom use a depthing tool for depthing. While I have posted this before, it may be of interest.
The attached photo shows a method I normally use in construction utilizing a milling machine. The wheel is allowed to freely rotate as is the the pinion on a pivot. The Mill slides are then adjusted until proper depthing is achieved.
Once achieved, the slides are locked in place and the mill spindle is utilized produce a pocket for either a jewel or other bearing. This assures retention of the depthing location and has out performed the depthing tool at least by my hand.
While a depthing tool is a simple device, its accuracy depends on the the tools accuracy and the accuracy of other procedures to complete the job. Errors no matter how small are accumulative and have effected overall function at the accuracy levels required for horological watch movements.

Jerry Kieffer

 

[DeweyC]

Talk to the librarian. He/She will know what you are looking for. I do have all the process sheets for the M21 so if you get stuck, I can send you a copy of say the staff and a hole jewel.

Daniels is kind of tricky (like most watch making writers). Lots of Easter eggs. Look up Jendristki or Perkins for full stories.

But, using a depthing tool to lay out a custom watch is very effective and accurate. Just depends upon on the condition of the tool and the skill in its use (keeping it perpendicular, etc).

 

[gmorse]

Hi AG,

Just depends upon on the condition of the tool and the skill in its use (keeping it perpendicular, etc).

The runners being exactly parallel across their entire range of movement is crucial. Unfortunately many of the now elderly watch-sized tools you may come across have either been abused and become misaligned, or weren't made properly in the first place.

One advantage of the tool is that you can easily feel how the wheel and pinion are meshing, and apply some resistance to the pinion to emulate the conditions in which it will work. A meshing pair may look as though they're transferring power smoothly, but fingers are a more sensitive tool.

Regards,

Graham

 

[Al J]

I have yet to see a proper engineering drawing (what I, as an engineer, would consider a proper drawing anyway) with complete tolerances for watch parts. Here's one drawing I snapped a photo of in someone's shop while visiting...

Unfortunately there are no real tolerances on the hole positions shown, just some tolerances on the diameters. The holes in the main plate at jewel locations are for fitting the jewels, so not reflective of tolerance is the hole in the jewels for diameter. It's a pretty amateur drawing to be honest, but the person who drew it isn't an engineer, although that certainly hasn't hurt his career.

I'm quite sure in real mass production there is a properly done drawing with geometric tolerancing that shows what the acceptable limits are (maximum material condition, minimum material condition, and all that jazz - quite different from the simple tolerancing systems many are familiar with).

Just keep in mind that manufacturing tolerances are very different from desired clearances like end shake for example - these often get confused.

Cheers, Al

 

[AGIreland]

I have yet to see a proper engineering drawing (what I, as an engineer, would consider a proper drawing anyway) with complete tolerances for watch parts. Here's one drawing I snapped a photo of in someone's shop while visiting...

View attachment 763383

Unfortunately there are no real tolerances on the hole positions shown, just some tolerances on the diameters. The holes in the main plate at jewel locations are for fitting the jewels, so not reflective of tolerance is the hole in the jewels for diameter. It's a pretty amateur drawing to be honest, but the person who drew it isn't an engineer, although that certainly hasn't hurt his career.

I'm quite sure in real mass production there is a properly done drawing with geometric tolerancing that shows what the acceptable limits are (maximum material condition, minimum material condition, and all that jazz - quite different from the simple tolerancing systems many are familiar with).

Just keep in mind that manufacturing tolerances are very different from desired clearances like end shake for example - these often get confused.

Cheers, Al

Thanks AI for the drawing, the reason I’m asking about tolerances is that I have a deckel pantagraph and I was thinking I could lay out the hole positions with the pantagraph using a 5:1 template then bore out the holes on the BCA jig borer. The idea was bore out the hole on the plate then attach the bridge plate and bore out the top plate. Hence the reasons as too what are the tolerances seen as I won’t be using a depthing tool.
This is a different method to what daniels does in his book. Would the lathe and a wobble be a better way to do it. I have a mechanical, electrical background but I wouldn’t have much in a toolmaking background.
How would I contact the librarian to get the drawings.

Thanks
A

 

[John MacArthur]

Hi AG,


The runners being exactly parallel across their entire range of movement is crucial. Unfortunately many of the now elderly watch-sized tools you may come across have either been abused and become misaligned, or weren't made properly in the first place.

One advantage of the tool is that you can easily feel how the wheel and pinion are meshing, and apply some resistance to the pinion to emulate the conditions in which it will work. A meshing pair may look as though they're transferring power smoothly, but fingers are a more sensitive tool.

Regards,

Graham

I agree with Graham that feel is important in adjusting depthing. But scribing two arcs and getting the prick punch at exactly the intersection is likely to introduce some error - I've heard as much as .005". I know I've had trouble getting what I think is adequate precision that way. What I do now is get the wheel-pinion pair running just right in the depthing tool, and then measure the inside and outside distances of the runners, add, and divide by two. This gives the center distance quite accurately. Then, after I do that for the adjacent pair, I can lay out the coordinates in CAD, and set up in the mill or jig bore with good DRO, and drill by the coordinates. I feel like I'm getting nearly an order of magnitude improvement in precision this way. I'm glad I've kept at it long enough to have afforded much better equipment.

Johnny