Looking for a Mainspring

[jdrichard]

I just picked up a Hamilton 974 and am looking for a Mainspring. Hunter and could not find the dimensions. I was successful with replacing a mainspring for an old german watch using a Cousinsuk generic one...want to do the same for this one

From Canada

[jdrichard]

From Canada

[jdrichard]

I just picked up a Hamilton 974 and am looking for a Mainspring. Hunted and could not find the dimensions. I was successful with replacing a mainspring for an old german watch using a Cousinsuk generic one...want to do the same for this one

From Canada

From Canada

[oldhippy]

Try here.

http://www.ofrei.com/page299.html

[jdrichard]

Try here.

http://www.ofrei.com/page299.html

Used there site to size it and bought a generic from cousinsuk, better price with cheaper shipping.

From Canada

[JohnR725]

I've uploaded image with the specifications for your mainspring. Just remember when you're looking for a generic spring it has to have the right end to fit American pocket watch. Then typically the modern White Springs for the same thickness are stronger than the original ones. Personally I always like to remove the old spring and measure that just to verify it does actually meet the specifications that you find the reference books because occasionally there's variations.

[jdrichard]

Thank you very much. I will get better at this with experience and a few (I hope) failures. I will measure the spring and see if I ordered the right one.

From Canada

[jdrichard]

My order was a 2.80 vs a 2.83. I hope this is not a significant issue. I matched it to generic spring available at cousins UK.

From Canada

[jdrichard]

Where did you find the reference information

From Canada

[syfre]

http://www.jewelerssupplies.com/mainspring-size-charts.html

[JohnR725]

The width of the spring was fine I looked at the cousins website before I posted my last message to see what they had.

All the dimensions in real life are critical but almost lucky to get what you can get now. So slightly narrower isn't an issue there tends to be some variation depending upon who manufactured the spring anyway. Length usually isn't an issue unless you go extremely long or short. Too short you lose running time too long it gets to be hard to get into the barrel and if you fill the barrel up you have no running time. The thickness or strength of the spring is the problem today. The white Springs are stronger than the blue for the same size.

Availability is an interesting issue. I'm attaching an image for an example. So originally you might have had several different sizes of spring for the same part number. Usually the thickness was the difference. This would correspond to the heaviest one would go in a 7 jewel watch the lightest In a 21-25 jewel watch. Today if you're lucky to get one the spring possibly to light for a seven jewel and often too heavy for a high jewel watch.

Then the reference I was using is this book "The E & J Swigart Co., Illustrated Manual of American Watch Movements" Which you can get is a physical book and as a PDF. So besides the parts listed for various pocket watches there's a section on mainsprings. Depending upon which company the mainsprings are listed by the model of watch it goes in other times it's by the part number.

[syfre]

The most important is the termination, modern mainspring don't used T-End style; don't think you can find that on cousins uk. Hamilton #318 mainspring are easy to find on ebay us.