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Mainspring question

kd8tzc
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kd8tzc WRT Addict

kd8tzc

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I understand the siz information when I buy a mainspring when the metric system us used, but when I try and buy one from the US, they seem to use a different system.  Can anyone explain how I can convert from the metric measurements to whatever the US side measurements are?

For example, if I am looking for 1.20 x .11 x 240 x 8.5 from the UK (all in Metric) how would I convert that to the other measurement system?  I thought it was just converting from mm to inches, but I'm thinking that is not correct.

Neverenoughwatches Distinguished Member

Neverenoughwatches

Posted
Posted
24 minutes ago, kd8tzc said:

I understand the siz information when I buy a mainspring when the metric system us used, but when I try and buy one from the US, they seem to use a different system.  Can anyone explain how I can convert from the metric measurements to whatever the US side measurements are?

For example, if I am looking for 1.20 x .11 x 240 x 8.5 from the UK (all in Metric) how would I convert that to the other measurement system?  I thought it was just converting from mm to inches, but I'm thinking that is not correct.

Is the Dennison measurement used ? 

Here is a conversion chart of dennison to metric. 

Screenshot_20230415-204258_Drive.jpg

kd8tzc WRT Addict

kd8tzc

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Is Dennison only for strength?  Would all the other numbers then just be inches?  So for my example of 1.2 x .11 x 240 x 8.5 would it mean that it would be in Dennison 3 x 10 x ?? x ??

 

It looks like all the dennison ones I see only have three elements though, so not sure what happened to the the item.

praezis Distinguished Member

praezis

Posted
Posted
46 minutes ago, kd8tzc said:

Is Dennison only for strength?  Would all the other numbers then just be inches?  So for my example of 1.2 x .11 x 240 x 8.5 would it mean that ...

Looks like all your numbers (width, strength, length, diameter) are metric. Width 1.2mm is very unusual but exists.

Frank

Neverenoughwatches Distinguished Member

Neverenoughwatches

Posted
Posted (edited)
1 hour ago, kd8tzc said:

Is Dennison only for strength?  Would all the other numbers then just be inches?  So for my example of 1.2 x .11 x 240 x 8.5 would it mean that it would be in Dennison 3 x 10 x ?? x ??

 

It looks like all the dennison ones I see only have three elements though, so not sure what happened to the the item.

The Dennison width is the metric height ( ignore where it says metric width as in modern mainspring sizing it is known height )The Dennison strength is the metric thickness. In the old sizes the third measurement was given in inched this we can easily convert to mm. The last modern size is the barrel inside diameter in mm, not really needed.

1 hour ago, kd8tzc said:

Is Dennison only for strength?  Would all the other numbers then just be inches?  So for my example of 1.2 x .11 x 240 x 8.5 would it mean that it would be in Dennison 3 x 10 x ?? x ??

 

It looks like all the dennison ones I see only have three elements though, so not sure what happened to the the item.

Do their size specs look like this ? The last size is the length in inches here we can be a little flexible in mm. The fourth size in Uk is barrel inside diameter in millimetres that size is not used in Dennison sizing of the mainspring. I guess the reason to use Dennison for very small  dimensions is ease of quotation compared to 0.00xx"

Screenshot_20230508-165211_Drive.jpg

1 hour ago, RichardHarris123 said:

It proves that the metric system is better, totally illogical. 

America still use imperial measurements far more than we do. 

Edited by Neverenoughwatches
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kerrmbit Member

kerrmbit

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Posted

Came across your post while trying to figure out similar stuff, and yeah, the whole metric-to-imperial thing can get confusing with mainsprings. I had to do some conversions myself, and for your example (1.20 x .11 x 240 x 8.5 mm), you can get close by converting each measurement to inches, but it’s never exact.


The width (1.20 mm) is roughly 0.047 inches, and thickness (.11 mm) comes out to about 0.004 inches. Length is easier – 240 mm is close to 9.45 inches. Sometimes, just to double-check, I’ll pull up https://ruler.onl/ and line things up on my screen.

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