Hopefully you’ve never had to worry about a watch spring bar. If one fails, it can be a bad situation – such as a watch hitting the sidewalk. This could result in permanent cosmetic damage and/or a crystal shattering.
Preventative maintenance is something I recommend, given my experience with a Milanese band. (The one pictured on my dress mod had previously been on another watch.) The friction between the band and a thinner spring bar (1.5mm) almost wore through it, like sanding down a toothpick.
Whether you need to replace a spring bar or two, or just want to make just you’re taking care of your watch(es), there are a few things to consider that might not be obvious at first.
Watch Spring Bar Length
Its not to hard to see that different watches require straps/bracelets of different widths. This width is dictated by the space between the parts of the watch called lugs. The width of this space defines the spring bar length.
The correct length spring bar is critical.
Watch Spring Bar Pin
The pin is the thinnest part that fits into the watch lugs. There are actually different dimensions for the pin depth and diameter, with the diameter being especially important. A pin with a diameter that is too big simply will not fit. A spring bar with a diameter that is small may or may not fit, but can move inside the lug hole enlarging it. This could open the hole enough for the bar to come loose – and cause serious damage. I am not aware if an enlarged lug hole could be repaired, but it wouldn’t be cheap and for some watches, i.e. a $250 Seiko SKX007, not practical from a cost perspective
Make sure the your watch has the correct spring bar pin diameter.
Watch Spring Bar Thickness
Spring bar thickness is a matter of durability and strap/bracelet compatibility. My dress mod was built using a Seiko SXK007 that came with the “Far” bar pictured above. This pin is a standard of strength and durability, but it’s is too thick to accommodate the bracelet I wanted to use. I am using ToxicNatos SlimFat bars in order to both fit the pin diameter of the watch and the barrel on the bracelet through which the spring bar is fitted.
For a pull-through strap (i.e. NATO/RAF), I always use the thickest, most durable spring bars possible. In the picture above, a fat (2.5mm) bar that fits the smaller pin diameter is shown. I like using these when appropriate. They are available from Seiko – great quality.
A 1.8mm certainly isn’t bad, but a 1.5mm thick (or smaller) spring bar isn’t all that robust. A thinner spring bar is best for a low-stress situation like a dress watch.
Shouldered vs. Shoulder-less vs. Flanged Watch Spring Bars
This is a bit more esoteric and matters mostly if you want to change your strap/bracelet easily or frequently.
The Seiko fat bar is the only one pictured that is does not have flanges. Flanges make a strap/bracelet easier to change, since they give a tool (especially a spring bar tool) something to grab onto. The Seiko fat bar came with a polyurethane dive strap. It was easy enough to remove the spring bars using a utility knife. I do not know if these same bars are used on the watch with bracelet, nor how easy/difficult it would be to access/remove a flangeless spring bar with a bracelet or thicker (leather, fabric, etc.) strap.
There is another type of spring bar that is not shown here: shoulder-less. A shoulder less bar is ONLY used with lugs that are drilled through. This means that the hole for the spring bar is drilled all the way through the lug and visible from the outside of the lugs. The ONLY practical way to remove these spring bars is by compressing them by pushing a tool through the hole from the outside. This is very easy and very popular with owners who like frequent strap/bracelet changes. However, if this type of spring bar was installed on a watch without drilled lugs, they’d have to be cut out with a Dremel or similar tool, potentially ruining a nice bracelet or strap. These spring bars are rarer, so this mistake would be unlikely. However, it’s the kind of mistake I might make in my quest to ensure durability.
Personally, a good spring bar is my preference over the other two types of attachment: screw tubes and fixed bars. That is a topic for another post, though!