What thread

Hi all

i have to make some small screws , a friend has measured one of his screws for me but the thread is odd , he said the thread I 1.2X0.3 but I can’t find that , a 13BA is

1.2X 0.25 and a metric M1.2 is 0.25 exactly the same so it’s possible that he has the pitch wrong ( possible with such a small screw ) or I haven’t been able to find it, so I thought I would ask the learned people on here, my BA set only goes to 12 BA but my small metric set goes from 1mm to 2.5mm so I tried a M1.2X0.25 in the threaded clock plate and the tap screws in although it’s very slightly loose.

Dell

Can the item in which the screw is to be inserted give any clues? Do you know where and when it was made? Are there any other fasteners on it that can be removed and measured?

Have you considered M1.4 x 0.3 as a long shot? With something that small, you should ask how he has arrived at those dimensions (e.g. thread gauge and loupe for pitch, micrometer for major dia.) and use the answer to assess which of the two offers opportunity for error or confusion.

I would also favor M1.4 x 0.3, it is common for the actual threads to mic undersize slightly which can be misleading.

Dell

According to the incredible thread list produced by Andy Pugh :-

No 12 Progress is 1.2 mm Ø by 0.3 mm pitch.

Not a thread series I knew of or have encountered but a quick Google this link which includes a tabulation of sizes :- **LINK**

https://www.sizes.com/tools/thread_progress.htm

"A thread series used in watchmaking in Switzerland, 19ᵗʰ – 20ᵗʰ centuries. According to de Carle, “the most popular modern Swiss screw thread.” As is obvious from the table below, the size number is the diameter in tenths of a millimeter. Thread angle, 50 degrees; depth of thread, 0.8 pitch. Depth of rounding, 0.093 × pitch; radius, 0.0732 × pitch.

The company sold ready-made screws, and issued a screw plate as a means of checking sizes. Much of the use of the series occurred when makers found it convenient to thread their own screws using the screwplate as a die."

Clearly legit but possibly old enough to be obsolete and, presumably, screws may be unobtanium off the shelf.

Clive

Edited By Clive Foster on 23/09/2022 20:12:27

Lowenherz Ø1.2 has a pitch of 0.25mm and a thread angle of 53°08" with flats on both root and crest. Since there are a lot of similar threads around this size it needs careful measurement to figure out the correct thread. What it is for and its origin may also help. I have had to make replacement Ø7 Lowenherz thread screws for a continental music box.

Martin C

Should also add, Lowenherz Ø1.4 has a pitch of 0.3mm.

Martin C

Edited By Martin Connelly on 23/09/2022 20:46:40

Thanks for all the replies because the clock is 1904 I think it’s probably the progress thread , I had heard of that thread before but forgot about it ( comes with age ) I first thought it was Thury thread ( again Swiss ) anyway my 1.2X0.25mm tap screws into the frontplate albeit very slightly loose so that’s what I have used , there is no real force needed they just hold the crown on top of the frontplate.

Thanks Dell

Hi alI,

hope that I'm not jijacking this thread, forgive me if I am. I need to know what threads are in the various bushes on a Stuart Turner 504 boiler. I'm not sure if the modern Stuart version has the same threads as the older ST one, perhaps someone could enlighten me?

Best regards

TerryD