Precision hole locating in watchmaking

[karlmansson]

This thread is a budding off of another thread in the Horological Tools forum.

I'd like to bring another issue to the table on the subject of precision drilling: precision hole locating for watchmaking sized applications. Center punching accurately? Using centering scopes in milling machines? Loupes or wobble sticks in lathes? Going from sketch or layout to actual hole is a process vastly greater than having a drilling setup that allows for it. I’d like to both discuss the centering of existing hole and the marking out and drilling/milling of new holes. I haven't really figured it out myself yet and I'd like to hear your best methods, if you'd care to share them.

Best regards
Karl

 

[DeweyC]

Karl,

This is a great topic. Hole location can go from the use of buttons to using a lathe with a vertical slide as a pointing machine or even a vertical mill. There is a lot in the literature and I will dig up some references.

If you go to my web page you will see how I use a microscope for milling and drilling on the small machines. I do use a centering scope in my 102 but you have to make sure it can be collimated (made coaxial to the spindle).

This area could also cover the use of a dial test indicator for centering work. But I use a wobble stick and physics for centering things like a jewel setting that needs a new jewel. (Brass faceplate and shellac method).

I may have some photos; will look through my LR library (love keywords!).

It would be helpful if you looked through my photoseries and let me know if I am missing something. Dushan and Jerry I am sure have material on these topics. And others we have not heard from probably have methods we have not thought about.

This is dear to my heart because as I said earlier when I first started out the best descriptions for precision setups came from Tubal Cain and the Argus Publications series for model makers. And before Archie's and Malcolm's books, the next step up was/were the two table top machining books.

FWIW, the Malcolm Wild book goes into detail on centering work in the lathe. This is critical for pinions. And there are very low tech ways to get this done.

We should all remember, Breguet and Frodsham were doing these things long before we came along. None of this is beyond the ability of the aspiring machinist. At one time, virtually any white male teen in the USA was exposed to this stuff. Today, it is almost mystical to most young people.

Pick one and let us know. Also, should this be a seperate thread?

Here is a simple method for centering a cutter from Wild (second photo):

Making a Clock Pinion

I did have to make the collet mounted micrometer head holder. There is a pin of a known OD (say 10mm) mounted in the center of the holder with a close fit. Set the micrometer drum at 5mm (radius from center of the 10mm pin) and adjust the micrometer body until it touches the OD of the pin. Now you have it adjusted to 5mm from center. Zero will be on center of the spindle axis. Measure the width of your cutter, adjust the micrometer to 1/2 the width and bring the cutter to the micrometer spindle until it touches. This will put you where you can now make a pinion in brass and see if the leaves are correct. No matter which procedure you use, always make the first pinion in brass to save the cutter.

I now do my wheel cutting in the 102 and center with the scope. But there is also a procedure where you can take a cut, turn the stock 180 degrees, take another cut and then use the slide rest to measure the distance between the two cuts and correct.

These and others are well described in Wild.

Here is information I have on use of microscopes:

Microscopes In Watchmaking

And here is information I have on basic measurement:

Measurement in Watchmaking

 

[DeweyC]

Karl,

Since you are early in your career as a watchmaker, here is another section that may be of interest. Will get you the references on hole location (both new and existing) later today.

Notes to Young Watchmakers

 

[karlmansson]

Thank you Dewey!

I'll have to revisit that cutter centering technique again to really understand it I think.

Looking forward to those references! I know how to layout and mark and punch holes for larger items but when we are dealing with very small tolerances I think the use of a free hand centering punch and scribe lines won't suffice. Of course, this is where the jig borers come into play. But for laying out a gear train from depthing, I'm trying to figure out how that would be done using coordinates. Or maybe the best approach is to scribe with a depthing tool and then use a centering scope in the milling machine?

For making new bridges or reaming out worn bushings, using a face plate and wobble stick for centering and assuring uprightness seems like a pretty failsafe method. It's when there are no previous holes to reference off of that I feel I'm not on soid ground any longer.

Regards
Karl

 

[Dushan Grujich]

I'd like to bring another issue to the table on the subject of precision drilling: precision hole locating for watchmaking sized applications.

G'Day Karl!

Perhaps it will be useful to You to download book "Technology of Watch Production". I have posted a link for download in one of our earlier discussions on use of rounding up tools, click here. In this book, one can find a number of useful techniques applicable by a watchmaker in a moderately equipped workshop. You shall also find answers to a question of precision drilling and location of holes including required tolerances for wrist and pocket watches.

Cheers, Dushan

 

[DeweyC]

Karl,

The book Dusan has is great. Forgot all about it.

As for how to lay out a one-off train, you are correct. Depthing tool helps to avoid built-up errors. You may be surprised just how "sloppy" a watch train really is. In absolute terms the limits are quite small. In relative terms they are pretty large.

A bore/center scope through the spindle (like on a Hauser) would be terrific. But, as you can imagine, there are ways this is done that worked long before these were available.

But, you can also mark the hole with a good center punch or drill a small starter under a microscope at the lathe/mill. Then I would verify each location with the depthing tool before final drilling.

I would center the sinks off my finished holes.

Think about how to use hardened steel jigs for filing guides. I even make them for drilling guides when I need to replace a post milled into a sink.

For bridges, look at Archie's books. It really is not hard to set up for radiused bridges. There are a number of ways to locate/drill steady pins/holes and screw holes. You probably want reamers for the steady pin holes though. On the early years, Hamilton actually used sleeves on the bridge to locate the plate screw holes; acted like a steady pin.

I never made a watch and never will now. I look forward to your progress. What are you going to do about the pallet fork? There are recipes for making pallets and escape wheels. Jewels have also been done; but ....

And remember, Daniels got his balance springs from Hamilton (992b balance springs). Sourcing parts is not a sin. When people make tourbillions, they often use an existing escapement (often a ladies Omega).

Very few people who completed a watch actually made everything. There are far too many subskills to learn and master in a lifetime. It would be like trying to master eye surgery, cardiology and urology in one lifetime.

 

[karlmansson]

G'Day Karl!

Perhaps it will be useful to You to download book "Technology of Watch Production". I have posted a link for download in one of our earlier discussions on use of rounding up tools, click here. In this book, one can find a number of useful techniques applicable by a watchmaker in a moderately equipped workshop. You shall also find answers to a question of precision drilling and location of holes including required tolerances for wrist and pocket watches.

Cheers, Dushan

Thank you Dushan, that's fantastic! I must have missed that one the last time you gave me the link, can't remember seeing it before.

I'll delve into it more in detail in a little while. So far though, the section on laying out holes states "center punching" as a part of the process. Not much on how that is done. How do you usually do it? In the staking set? In some sort of accessory to a milling or drilling machine? I remember seeing some type of center punching jig a while back with a magnifier with cross hair that was replaced with a center punch of the same diameter. Made lining the punch up with layout lines a little more precise. I think it may have been Adam Savage that used it in one of his builds... He loves his gadets.

Regards
Karl

 

[karlmansson]

Karl,

The book Dusan has is great. Forgot all about it.

As for how to lay out a one-off train, you are correct. Depthing tool helps to avoid built-up errors. You may be surprised just how "sloppy" a watch train really is. In absolute terms the limits are quite small. In relative terms they are pretty large.

A bore/center scope through the spindle (like on a Hauser) would be terrific. But, as you can imagine, there are ways this is done that worked long before these were available.

But, you can also mark the hole with a good center punch or drill a small starter under a microscope at the lathe/mill. Then I would verify each location with the depthing tool before final drilling.

I would center the sinks off my finished holes.

Think about how to use hardened steel jigs for filing guides. I even make them for drilling guides when I need to replace a post milled into a sink.

For bridges, look at Archie's books. It really is not hard to set up for radiused bridges. There are a number of ways to locate/drill steady pins/holes and screw holes. You probably want reamers for the steady pin holes though. On the early years, Hamilton actually used sleeves on the bridge to locate the plate screw holes; acted like a steady pin.

I never made a watch and never will now. I look forward to your progress. What are you going to do about the pallet fork? There are recipes for making pallets and escape wheels. Jewels have also been done; but ....

And remember, Daniels got his balance springs from Hamilton (992b balance springs). Sourcing parts is not a sin. When people make tourbillions, they often use an existing escapement (often a ladies Omega).

Very few people who completed a watch actually made everything. There are far too many subskills to learn and master in a lifetime. It would be like trying to master eye surgery, cardiology and urology in one lifetime.

Thanks Dewey, sound advice. I was thinking I would make jewels as well but I've reconsidered. I'm going to get commercially available ones. The pallet fork I thought I'd make myself. The entire escapement for that matter. Seems like on of the more rewarding (and so also potentially frustrating) challenges in making a watch.

I'll have to experiment a bit with the techniques you mention! I just got a small milling machine and I'm thinking about either finding or building a centering scope that can be collimated.

Regards
Karl

 

[gmorse]

Hi Karl,

I remember seeing some type of center punching jig a while back with a magnifier with cross hair that was replaced with a center punch of the same diameter. Made lining the punch up with layout lines a little more precise.

I have one of these optical centre punches and it is very useful, once you've established the position for the centre. Mine is a Dankroy, and I don't know if they still make them, but they are available from other manufacturers.

Regards,

Graham

 

[Dushan Grujich]

So far though, the section on laying out holes states "center punching" as a part of the process.

G'Day Karl!

It of course is not the only way, look at the page 255.

Cheers, Dushan

 

[DeweyC]

Karl,

Just to cover bases, there are two holes you locate without any reference to coordinates. The center wheel holes.

These are used as datum for later positions. You may have figured this out; but there it is.