FEF 380 Mainspring

[mcoulton]

Hello

I've never had to order a mainspring before and I'm look for one for the FEF 380 movement with a measurement of 1.45 x 9.5 x 0.105 x 300mm. I've tried looking for one on Cousins and Otto Frei with the latter using terms of Dennison Width (Barrel Diameter?) and Dennison Strength - don't know what this is.

Would someone be kind enough to:

A.) tell me what the Dennison Width and Dennison Strength refer to 

B.) where can I find a mainspring with these dimensions? I couldn't find it on either Cousins or Otto Frei - though my searching skills may not be that great.

Thanks in advance for any help that can be provided.

Michael

[JohnR725]

Watchmakers are creative people we like to have different measurements. Somewhere out there I know there's a PDF that explains how and why Dennison for mainsprings came into existence conveniently I don't remember where it is. But I do have the cross reference chart below. Typically in this country you'll find mainsprings marked in metric and Dennison and of course the length in inches occasionally they'll use the Swiss and have length in millimeters. Then yes in addition to the nifty Dennison there was a Measuring tool to go with it for measuring your mainsprings.

Oh and then the diameter that supposed to correspond the diameter of your barrel so you can push the spring in a you don't have to use a mainspring winder.

Then the link below cross reference all your parts. You can click on the mainspring looks like it goes into a heck of a lot of watches. But the get a mainspring number they go to the homepage of this company's website and see if they have it? Looks like it's in stock

http://cgi.julesborel.com/cgi-bin/matcgi2?ref=FEF_380

http://www.julesborel.com/s.nl/it.A/id.28656/.f

 

Mainspring - DennisonChart.pdf

[mikepilk]

Another way to look up mainsprings is in the GR database.

If you do a search on Cousins documents for "GR mainsprings"  you will get a list of the GR mainspring catalogue pages.

It's worth downloading them.

Pages 1-10 list by manufacturer. In your case FEF refers you to pages 87-88,  which gives 

The number in the second column is the GR reference. You can then search on Cousins for "GR3969"

 

[JohnR725]

8 hours ago, mikepilk said:

GR database

What is interesting is if you go to the first link I had above click on mainsprings in addition the best fit number you get the Size and a confusion? I'll paste the numbers below they usually do give the GR number but they're giving us a different number?

Looking up the mainspring below in the mainspring catalog it does agree with the mainspring size they have listed below. Which is almost identical to the listing above sizes are off by a fraction of a millimeter for both the width and the strength. Which suggests that the material house of this came from probably doesn't stock the fractional size mainsprings. But I don't think that's enough of a size difference the matter.

MS-510M
 MAINSPRING 1.40-.11-320 9,5
 GR 3699

 

 

[mcoulton]

Thank you both very much for your help and the links provided. I will look into both Jules Borel and Cousins.

 

Regards

Michael