American Watch Threads

[chris mabbott]

Last night while going through some boxed stuff and I found that I had some small sets of taps, ranging from 0.20mm – 2mm, yeah, I know…cUUute 😆 these little turds are precioso. But it started me wondering what was the standard thread model that American watch manufacturers used for their fasteners? I realized that I had no flamin idea.
These are American vintage taps, for watches, and they’re metric.

Did they all use metric or imperial type thread, or was each company using their own specialized type, ya know, to protect their parts from being used in other watches.
Did they use a standard metric fit to make it easier for export to Europe ?

When you look in the old catalogs you can see, in the supplement section, that various tools are offered by the manufacturer. Taps for the various screws being one of the items. Thing is, they do not mention thread type, rather a set of taps for 18s watches.
Even the screws they provide are not by type/size, rather for where they belong, I.e. plate screw, balance screw, jewel setting screw etc..

Just curious if anyone knows or if someone has a micro thread gauge and has measured?

[namonllor1953]

Hi Chris,
I didn’t think Imperial threads ran that small but truth be told. a bolt size of 0000 is 160 TPI.; compred to a metric .2 is 114TPI or something like that;
I always asuumed that they were metric but, maybe…….who knows..

[chris mabbott]

Hey Ren,

good point buddy, I”m not sure either if imperial goes that small.
I was kinda curious because the countries with the closest ties to the UK are still on the imperial system, and according to the way it is still going, these countries will continue to stay that way. So I wondered, if, way back then, the watch groups had adopted metric or some morphed version of both?

Maybe I’ll dig out an old movement and try the taps to see…

[david pierce]

Chris,
Unified threads are designated by the number of them you can cram into one inch. Metric threads are simply measured from peak to peak or valley to valley. Since you probably do not have an optical comparator or a Unitron measuring microscope, you can still measure them by rigging something up on your milling machine or lathe. For the lathe, stick a blob of Rodico to a spot on the lathe chuck (power off) and stick the head of the screw into the Rodico. Mount a small sewing needle (with Rodico) to the cross slide and attach an accurate metric dial indicator to measure the movement of the cross slide. Then using some form of magnification (a loupe) move the sewing needle (and carrage) from thread peak to thread peak and check the amount of travel on the dial indicator. As far as I know the entire watch industry switched over to metric many years ago and I would guess that every watch screw you are going to come across will be metric.
david

[chris mabbott]

Thanks David, and yes, it makes perfect sense that they would use metric, I just wasn’t certain as even today, the battle goes on to standardize and bring in the metric system to the US & the UK, in full that is.. So really, when you think about it, it is kinda amazing that 120 years ago the watch industry tooled up for the european system. This is the conundrum that caused a mental traffic jam in me noggin

[gerene]

That is indeed amazing but I am happy about it. Being brought up in a pure metric world I still have difficulty using the imperial system. I was first confronted with it when I lived to the US in the late eighties and had to go shopping buying ounces, pounds, fluid ounces etc. It’s all a matter of getting used to, but adding mm or decimal fractions for me comes more natural than using a system with 1/2, 1/4; 15/16 etc. My mind can’t cope very well with that

Jan

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