Sourcing Replacement Hairspring.

[nad]

Watched Marks video on hairspring repair again today in prep to trying it myself on a scrap movement. Needless to say, for a first attempt it didn't go totally to plan. Twist reduced but now have a few "waves" in the outer coil.

Replacement would be the answer but being a vintage movement spares could be difficult to source, e.g. obsolete part number.

In a similar way to Marks explanation on mainsprings, are there any standards for hairsprings to aid sourcing at a materials house? Or is it by reference to movement calibre only?

Thanks.

[Geo]

In a similar way to Marks explanation on mainsprings, are there any standards for hairsprings to aid sourcing at a materials house? Or is it by reference to movement calibre only?

Thanks.

I'm sure it it will be by make and calibre.

[clockboy]

Getting the correct hairspring is very difficult. You need to know its length, strength and also you need the correct t centre stud. 

I have accumulated lots of hairsprings over the years from eBay but it's amazing I never seem to have the correct replacement when needed. Here is a good explanation I copied from the web a few years ago

 

First is the diameter of the hairspring. It should be roughly half the diameter of the balance wheel.

Next is number of coils. 

The correct hairspring mating to the balance wheel should hang approx. 1/2 inch.

So, you take the tail end of hairspring and make a small hook and hold up hairspring by centre coil and gauge the distance of how far down the hairspring stretches when the balance is hooked on.

Considering all of the above, you might be able to order the correct spring if you still have the old one. You could compare the diameter and number of coils.

Once you pass the 1/2 hanging test, you then cut out small section of inner coil so to bend in to fit the hairspring collet. Try to make cut and bend place collet in centre.

Then you vibrate the hairspring by holding it up at locations of the end coil till you get the balance to turn back and forth pretty close to a similar watch balance. There are a few different methods and tools to vibrate hairsprings and you don't have to spend big money.

The point on the hairspring where you hold it, that makes the balance turn in same speed, is the spot where the spring will be at the regulator. So you don't cut there, you leave some slack so you can stake it. 

 

The vibrating part I just use a watch with a second hand and count the vibs.

Below is the only company I have found that sells new springs BUT they are incredibly slow. The majority of springs sold are without the centre collet.

 

http://www.britishprecisionsprings.co.uk/index.html

[nad]

Thanks Clockboy, not that straight forward then but thought I'd ask a question