Jump to content

Mainspring Sizing

Lawren5

By Lawren5
in Watch Repairs Help & Advice

 Share

Recommended Posts

Lawren5 WRT Addict

Lawren5

Posted
Posted

I need to find a replacement mainspring for a Ball pocket watch which uses the Hamilton 992B movement. The broken mainspring measures 2.82 mm wide, 0.16 mm thick/strength and 23.5 inches long. The closest replacement I can find has all the right specifications except that it is only 20.75 inches long, nearly 3 inches shorter. Would using a short mainspring present any problems?

Link to comment
Share on other sites
Lawren5 WRT Addict

Lawren5

Posted
  • Author
Posted

I don't think the 534B will work because it has a width of 3.0mm whereas the broken mainspring measured 2.82 mm. The 534-718047 with a 2.80mm width is the one I've been considering and should work if the shorter length is not a problem.

Link to comment
Share on other sites
JohnR725 Distinguished Member

JohnR725

Posted
Posted

what was bothering me in the back of my mind is I worked on a ball watch and there were some differences and I just can't remember what they were? then before you remove the mainspring did it seem like there was additional space in the barrel for something wider? It's unlikely that they made a custom mainspring for the watch so it would have to be one of the Hamilton mainsprings. so I'm giving you the complete Hamilton 16 size section so you can see what once was available and what is currently available hopefully.

ham-ms.JPG

ham-mb.JPG

Link to comment
Share on other sites
JohnR725 Distinguished Member

JohnR725

Posted
Posted

usually the thicker part of the barrel lid isn't a problem because if you put the arbor in the lid that corresponds to that diameter.

I have an image from the 1946 Hamilton material catalog. Basically were down to they used the mainspring for the Hamilton 992 not Hamilton 992B. You notice in the catalog here when it came to end style both the 534 and the 534B are for motor barrels. 

so looking at eBay searching for 992 mainspring keeps coming up with 992B mainspring but I did find a couple in 992 and at least one of them is a white spring which typically makes it newer. The older blued spring is depending upon who made them can hold up and be very nice condition or they can be set and occasionally they get rusty not always noticed by the seller.  Of course getting the white spring means that while you have a whole bunch of choices a very long time ago typically on the modern spring they've consolidated all those choices down to 1  maybe 2  if you're lucky.

 

Hamilton 1946 catalog mainspring list.JPG

Link to comment
Share on other sites
 Share
Go to topic listing


  • Recently Browsing

    • No registered users viewing this page.

  • Topics

  • Posts

    • oldhippy
      Movement inserted from crytal side

      By oldhippy · Posted

      Before putting it back in the case I would fit the hands and use a pin vice on the stem to make sure the hands were in line. 
    • Jon
      Introducing myself

      By Jon · Posted

      Hi there  
    • Jon
      Movement inserted from crytal side

      By Jon · Posted

      Put the movement in a movement holder and it will be supported as you push down on the setting lever post to release the winding stem. Make sure the post is over the shoulder of the movement holder so what you are pressing down on is supported. As a general rule, hold the movement and not the movement holder. Replace the hands when the movement isn't in the case and support the centre jewel (if it has one) on a hard surface or staking block when replacing the hands to stop the jewel accidentally moving or even coming out. A dedicated movement holder with a central jewel support is even better, but pricey
    • JohnR725
      Main spring

      By JohnR725 · Posted

      It might help us if we knew which watch like model number.
    • Zedster
      Movement inserted from crytal side

      By Zedster · Posted

      Hi, guys I have a bit of a predicament and hopefully, somebody can advise. I'm working on a Roamer MST 521 where the movement is extracted from the crystal side. I'm now at the final hurdle where I need to replace the movement back into its case but I'm not sure of the correct procedure. I still need to fit the hands but that's where the problem lies. If I insert the winding stem to test the hands for correct alignment I will need to turn the movement over to release the stem again it's the spring-loaded type and needs a small bit of force to push down but with the hands fitted, I don't think I can do this on a cushion without causing some damage to the hands and that's the last thing I want to do, this watch has already been a love-hate relationship and I'm so close to boxing this one off which I'm counting as my first major project.  The other option is to case the movement then fit the hands and hope everything is okay. I've already broken the original winding stem but managed to find a replacement, the last one in stock, so I'm a bit reluctant to keep removing it. Any suggestions would be appreciated. 
×
×
  • Create New...