How to size a spring bar

[Richard1888]

Here is a question that I have been unable to find an answer for online. How do you choose the correct size of spring bar for a watch?

 

I have a box of various size spring bars and I have made the mistake of choosing one for a 20mm watch lug that had a barrel that just fit in.

You can manage to get this in but it just about impossible to get back out and I had to resort to a pair of cutters to get it back out again.

 

So if you have a particular lug width, how much of that should be the barrel of the spring bar and how much should be left for the springy part?

 

Thanks.

[ro63rto]

Measure collar to collar

 

 

 

Little more detail

 

http://blog.esslinger.com/how-to-measure-a-spring-bar-for-a-watch-band/

 

Sent from my Honor 5c

 

 

 

 

[oldhippy]

I used a spring bar gauge which was free with Apollo straps, as I stocked them. 

[Chopin]

If I need 20mm I'll get ones that are a few millimeters longer than that... Did a small test recently on a watch that had its original springbars. They were 3mm longer than the lug width I believe...

[jdm]

You could have a spring bar that when extended is 10mm longer than the lug width. It just depends by the springs being used.

[vinn3]

Richard;  welcome to the forum:  there is a lot TO BE LEARNED, about spring bars.  for example: seiko bracelets have a small diameter spring bar that only they sell.  "a good spring bar can save a watch".  and - a good watch maker can drill out the hole to fit an   after market spring bar.  (my opinion only).  vinn

[jdm]

39 minutes ago, vinn3 said:

for example: seiko bracelets have a small diameter spring bar that only they sell.  "a good spring bar can save a watch".  and - a good watch maker can drill out the hole to fit an   after market spring bar.  (my opinion only).  vinn

It is not so. All Seiko watches except certified diver's have totally standard spring bars. Only diver's have "fat bars", 1.1mm at the ends, 2.5mm at the body.

[oldhippy]

There seems a lot of fuss about spring bars and how to fit the correct size. They are telescopic so they will fit many sizes, it is just common sense on what size to use, but do not expect a 8mm size to fit a 20mm width strap. This is the main type we had in stock.  

[jdm]

Put simply, the intended lug width is on all and any spring bar box. They are not universal, each size and application has its correct spring bar.

 

 

 

 

[vinn3]

it is so.   i have a speed master with the original bracelet.    check it out.  you are right about the watch case,  not the bracelet.  vinn 

[vinn3]

SORRY,   seiko "speed timer"  with original braclet.  vinn

[Poljot]

I do realize that your question is 3-year old now

Length: mm

Bar diameter: Ømm

Pivot diameter: Ømm

Pivot length: Ømm

Shape: Single (Non-Telescopic) or Double shoulder

Single or Double Flange

Material and Coating: Stainless Steel or Gold Plated, etc

I am sure that more variations exist. Often we get lucky to simply confirm Length (between the lugs) and Bar Diameter, but today I learned that some vintage Omegas from 1930s have extra large 1.2mm lug holes, and will require 1.1mm Tip spring bars, not the "regular" 0.75, 0.85, or 0.9mm. But to answer your question, "usually" 20mm (between lugs) spring bar is about 23.00-23.50mm uncompressed. 

[oldhippy]

This is all you need to measure what size lugs you need.  

[familyguy]

If you measure across at say the 20mm mark, is it exactly 20mm or is it 20mm plus a few extra mm ?

[familyguy]

I recently ordered a container of spring bars from Ebay, 8mm thru to 25mm, country of origina unknown but more than likely China. Each has their own compartment marked with the size, I assume that the marked length corresponds to the watch case lug width.

I went through each one and checked the extended and compressed length dimensions with a set of digital calipers - here are my findings, while I have put lengths to the nearest 10th mm this may not be fully accurate as I was not 100% certain that the spring bar was truly at 90deg to the caliper jaws, however the dimensions are a good guide, if you have a collection of unknown spring bars measuring the extended length will give an idea which lug width they will suit.

Length    Compressed    Extended
25mm     24.80mm        27.5mm
24mm    23.78mm        26.8mm
23mm    22.98mm        25.8mm
22mm    22mm        24.83mm
21mm    20.95mm        23.80mm
20mm    19.94mm        22.80mm
19mm    19.05mm        21.75mm
18mm    18.01mm        20.85mm
17mm    16.81mm        19.60mm
16mm    15.71mm        18.75mm
15mm    14.28mm        17.36mm
14mm    13.82mm        16.57mm
13mm    13.02mm        15.52mm
12mm    12.1mm        14.4mm
11mm    11.05mm        13mm
10mm    10.17mm        12.25mm
9mm    9.3mm        11.1mm
8mm    8.5mm        9.45mm