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Mainspring barrel inside diameter

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Greetings everyone,

I'm relatively new to this hobby, having been involved for about 1.5 years now, and I'm thoroughly enjoying it. I would greatly appreciate any information you could share with me on the following,Thank you!

Good afternoon,
I'm reaching out with a question regarding the inner diameters of mainspring barrels for Waltham, Hamilton, and Illinois pocket watches in sizes 16-18. I would prefer this information to ensure I order mainspring winders with the correct diameters for these watches. Unfortunately, I've been unable to find this information online, and I'm wondering if anyone can provide it or direct me to a reliable source.
As I'm currently away from home, I don't have access to the barrels to measure them myself.
Best regards, Dave

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1 hour ago, Dsquared said:

I order mainspring winders with the correct diameters for these watches.

Out of curiosity where you going to order these mainspring winders from?

What about the other issue if you purchase modern mainspring winders they may or may not work at least as the handles will have issues. Specifically modern handles are designed for modern Springs and vintage watches seem to have a lot of variations unfortunately it's not that simple usually end up on some occasions you end up having to use multiple sets of handles and/or winders to find something that fits. Then I would probably have to sit down and measure as to whether there actually is sort of a?

This post is a compromise to the question you have I have a picture below. The mainspring winder on the very left-hand salad does exist and I'm not a big fan. The center winder is the standard one that I use 90% of the time so I could get to the diameters of those and that would cover almost everything. At least as far as the diameters go. Then the set on the right-hand side would work if you can afford it because it tends to be pricey unless you're just lucky purchasing it like I was and then there is the handle issue which I brought up the a get you some pictures of that.


For the center set this is what the handle looks like it's interesting in that it actually has two separate books because the center part can move in and out so when it's all the way out like it is now would be for a bigger mainspring and you can push it in for smaller diameter Springs. No notice is just a protruding in all and that's the other little problem a lot of the mainsprings of pocket watches could be left-handed Springs like typically 18 size full plate watches could be left-handed and there are few others it could be. So this is why this set is so nice to go in either direction


Then in the modern set is we will call it on the right-hand side the handles themselves common three configurations basically the image below is the vintage handle this is for all the blued steel Springs or for Springs that are diameters that your handle may not fit as I said this seems you a lot of diameter differences of the center part of the spring and you may not actually have a handle of the modern type which will show what a moment that's going to fit and for blued steel or older Springs this is the Handle which by the way I don't think they sell anymore. It's what the older sets used to have


Then this is what the newer handles look like because of the design of the mainspring and how tight it goes on the arbor and its sizing the book is ground into  the metal and doesn't actually protrude out which is why it's a problem on vintage or odd size Springs.







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I had a few movements apart and maybe this will help with your original question, Elgin 16s inside barrel diameter 16.23mm, Illinois 16s inside dia. 17.06mm, Waltham 16s inside dia. 17.9mm and Hamilton 18s 17.6mm, there are different models in each size and make so there larger or smaller diameters, but as you can see one or two winders might be all you need for most.......just borrow JohnR's haha

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One of the minor catches of knowing the diameter of the barrel is its possibly useless. This is because typically with American pocket watches you need to wind the spring into the winder leave a little bit out put all of that into the barrel. Rotated until usually the protruding T or T brace in a case make sure the protruding tea party is over the opening it has to go in push it in and hold it down with something and then you can inject spring. This means that winder actually has to be smaller than the particular barrel. And yes someone in the group we have pictures of all of this

Then Wally did remember to measure one of my sets I wasn't quite sure about the numbers they seemed a little strange. Then while on another group notice somebody asked a similar question so I went looking to see if I can find an answer and I did get an answer from the link below where we get this Stepping out the important part


Unfortunately it's in inches. I did my measurements in metric. We really need the catalog that's because when I look at the numbers I got for measuring myself that I have it work versus the other set that I have at home that I don't quite like as much but I thought there identical sets I find that some of them are very similar in size and the others have differing sizes.

On 2/11/2024 at 1:18 AM, Dsquared said:

sizes 16-18

Fortunately were only concentrating on two sizes and we seem to have some variations. It may be the difference in the various micrometers I used so the work set 16.2 mm which corresponds to 0.631 inches and the set at home at 16.27 mm. Then the next one down in size is 15.2 versus home of 15.08 which corresponds to 0.594 inches. I have a feeling they're not exactly an exact thing. Because more than likely the different size watch company barrels very and they might conceivably very because they have mainspring variations. Should probably check that out to see what variations we get for mainspring sizes for the various watch companies

Then as I suspected I did track down A catalog page


You'll notice not a lot of information other than 18 size and down

You can find the catalog page here Along with a whole bunch of other catalog pages and the whole website covers mainly staking cents but it looks like the price lists covered everything


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I wanted to express my gratitude for your comprehensive response. It's packed with valuable information that will greatly assist me in my search for a mainspring winder. I apologize for the delay in getting back to you; I'm currently abroad from the UK and going through a hectic period.

Initially, I was eyeing the K&D Robbins 126 on eBay. However, the high shipping costs and VAT made it less feasible for me. I also considered purchasing only the Bergeon sizes I needed from Cousins, that would be over £200 but then I realized I would be limited to just those sizes. That being said, I'll definitely keep Bergeon in mind and explore the possibility of acquiring a set similar to the one you mentioned in your description, perhaps like the K&D center one.

I think this is the way forward for me I am looking on EBAY daily.

Once again thank-you.

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Thank you for your introduction and welcome to this friendly forum.

We all look forward to your contributions and continued involvement. 

If you are fitting a new mainspring you do not need mainspring winders. They are packaged in such a way they are press fit.  

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Hello Oldhippy.


Thanks for the welcome.

Not your real name I guess😀

I understand what you are saying and have bought from UK suppliers, yep work great I have also done a few by hand which is interesting but me being me I would love a set of winders, so still looking.

Thanks for the help and info.

Regards Dave.

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4 minutes ago, oldhippy said:

If you are fitting a new mainspring you do not need mainspring winders. They are packaged in such a way they are press fit.

Normally that answer would be 100% correct except let me quote something.

On 2/11/2024 at 1:18 AM, Dsquared said:

Waltham, Hamilton, and Illinois pocket watches in sizes 16-18. I

American pocket watches specifically 16 and 18 size. The problem is The end of the Springs do not really lend themselves to being pushed out and staying where there supposed to be there is a procedure. Which we've covered before somewhere in the group in other words the end has to go into whatever it goes into and then the spring can be pushed out.

Because as curious about something and were only having Waltham Hamilton in Illinois what happened the Elgin? But okay we don't need Elgin so here's an example of the problem with the mainsprings. Oh and this isn't 100% because I know in the case of Elgin they had some earlier springs that were discontinued and I'm pretty sure when there were discontinued they actually had upgrade mainspring barrels but that was like 100 years ago is there are some vintage Springs that don't actually exist anymore.


Then for Waltham they do love a few with hole ends Which if they weren't original spring you could push out. Providing yes there's always complications a lot of the original American Springs came in rings that were physically bigger than the barrels because I think they didn't want the Springs to set prematurely. Then the hole itself is misleading as it needs to have a special shape the modern Springs don't you have to modify it so you can try pushing it out and if you're really really really like he may be on hold which is a really nice thought because those Springs are a pain in the something.


Oh and minor misleading things again typically the Illinois T end the protruding part has been machine to be around in diameter whereas the modern Springs are just stamped and they will be square. So either you have to open up the whole just a hair to get them in or you have to round your end.


11 minutes ago, Dsquared said:

Hello Oldhippy.


Thanks for the welcome.

Not your real name I guess

What is interesting in discussion groups are how people identify themselves and of course the really clever people usually have an icon or picture to represent themselves. Versus us lazy people where I just never got around to having an icon or a picture. Occasionally has crossed my mind I can't think of anything and just to make things more fun in one of the other groups I use my real name.

This then becomes interesting when people post questions on multiple discussion groups and then if I answer the question on multiple groups they don't realize that it's the same person.

Then since I've never actually measure the inside diameter of mainspring barrels if you look at all the numbers up above I'm guessing in real life there probably variations between the various barrel diameters especially when there can be differences of mainspring lengths.



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Thanks for all the helpfull info guys very much appreciated there is a wealth of knowledge on here it is amazing.

My mission now will be to purchase a K&D set more than likely a 126,and take it from there.

Regards Dave.

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Would you mind winding it in by hand? That's what I do when the bridle is T-shaped. It takes quite a bit of practice, especially for small wristwatch size movements (fiddly) and I've never tried it with a pocket watch (the only pocket watch I've had apart was the Unitas 6497) so perhaps in that case the spring would be too hard to wind by hand, no?!

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