Watchmaking - Making Carbon Steel Hairsprings for Watches, Clocks and Other Small Mechanism.

good day Chris here and welcome back to click spring one of the projects that I have underway at the moment is the construction of a dial indicator which as it happens has a need for hairspring to provide a small anti-backlash Force within its gear Trin despite being a standard component of a mechanical indicator it's probably more common to think of a hairspring or balance spring associated with a balance wheel of a watch or clock so not surprisingly it's within the watchmaking textbooks that the detail can be found on how to make them with much Theory and practical advice on the fabrication process so be sure to check out the list of references that I've put together below there are several overlapping generations of technology to consider starting with the non-heat treated approach for an early Verge movement and if you'd like to see a demonstration of that process then be sure to check out the selective Lite here on YouTube you'll find a link below a more modern approach is to use an alloy with specific temperature properties that simplify ifes the temperature compensation for a mechanical watch the process to form the spring is much the same as what I'm about to go through but there's a heat treating process for the alloy that tends to be more complex than we're usually able to reproduce in a home shop and of course the most recent generation of hairspring technology is a step jump entirely using an etched silicon process the predecessor to these modern developments that dominated mechanical watchmaking for a long time was the carbon steel hairspring paired with a bimetallic split balance wheel and it's the formation of this typee of hairspring that I'll investigate in this video for A flat spiral spring the tool used to form the Springs generally looks something like this the small recess within which in this case two Springs are to be wound defines several of the Springs characteristics its inside diameter limits the amount of material that could be drawn into the space the number of openings through which to draw in The Wire defines the spacing between each of the spirals two openings permits two pieces of wire to be wound together and so the space between each spiral equals the thickness of the source wire three openings winds three pieces of wire together and so the spiral spacing becomes twice the thickness and so on this effectively determines the length of the spring for a given recess diameter and wire stock in addition to the material itself and the width and height of the spring cross-section this sets the Spring's performance characteristics which then guides how the spring can be used for example a hairspring can be matched with a balance wheel with a suitable moment of inertia so that together they'll give a desired period of oscillation and otherwise meet the design requirements of a particular watch or a spring can be selected based on its ability to provide a suitable restoring Force within a small gear train like the sort found in a dial indicator the role of the brass winding aror is to catch the inner end of the wire inside the recess to enable the wire to be pulled in as the handle is turned in this case a couple of narrow slots and a closing screw will do the job of gripping the wire with the screw also acting as a bearing for the cap that sits on top during the winding process the carbon steel wire from which the Springs are made is usually formed flat using a Precision Rolling Mill or perhaps drawn through through Diamond D to give the required thickness for the spring I'm most interested in proving out a convenient rolling process suitable for the home shop so that's where I've directed my effort a good source material for the wire is plain music wire either as guitar strings or in the form provided by suppliers like kns with a bit of testing I found that the kns number 499 wire will roll down to the dimensions that I'd like for the indicator spring although as supplied it has a spring temper which is too hard for rolling so it first needs to be annealed by heating to a cherry red color and then being allowed to slowly cool after this the wire is dead soft and ready to be rolled flat now gener wire rolling is a specialized activity but there's a tool that many of us have on hand that if used carefully can be adapted to get a decent result and that's a clamp style nuring tool by replacing the standard nuring Wheels with smooth hardened rollers it can generate the required compression force in a controlled way and by using this tool we also get to leverage the other benefits of the lathe as the platform on which to carry out the job for the rollers I'm using 01 oil hardening steel formed to the size of the knurling wheel that the tool would usually take a MIG welding nozzle held in place with tying wire works well to guide the spring wire stock onto the rolls and the wire stock is most easily managed using spools as it's fed through the rollers so a couple of simple discs grooved to accept the wire will do the job I've made the spools to be interchangeable on a common mandrel so once the wire is fed onto one it can be swapped out and the process repeated the final condition of the rolled wire and in fact the final spring itself depends a lot on the initial condition of the raw stock before rolling in particular the wire needs to be completely free of oxide and in a well polished state an initial closing force is set using the nerling tool frame with a small Mark helping to keep track of that setting as the rolling progresses then with the lathe running in Reverse The Wire is pulled through its first part through the rollers and load it onto a spool these small Clips have a leather pad glued inside and work well as a brake to help keep the wire on the spool they also generally help keep the wire manageable as the job progresses while prototyping this process I used a couple of permanent magnets to provide support for the spool as it feeds the wire into the roller tool to get an idea of where the bearing should best be placed before committing to making any supporting parts now that initial idea ended up working well enough that I've kept using it for now but it wouldn't take much to make this Arrangement a little more robust in future if it should need to be [Music] so the wire now travels in a controlled manner through the roller with one of those small brake clips catching on the saddle of the lathe and serving to drag on the spool as it's feeding out providing a light tension to keep things orderly [Music] from here the wire is fed from spool to spool while gradually reducing the gap between the rollers on the way to final [Music] Dimension now depending on the amount of rolling to be done the wire may take on more of a work hardened state that is reasonable to accept in terms of the damage risk to the rollers in which case the wire is simply analed again as before eventually the wire is brought to its final Dimension and I found that making multiple end forend passes at the final roller setting to be a good way to get repeatability in both the dimensions and surface finish from here it's into the winding process securing the wire on the winding Arbor of the tool and then carefully winding it into the recess [Music] [Music] once fully wound the retaining screw can be removed and the spring material securely enclosed for heat [Music] trading naturally would prefer to see the Springs emerge from this process relatively free from scale by far the most effective substance I found for minimizing heat treading scale is powdered boric acid mixed with deed alcohol when generously applied it completely envelopes the workpiece in a molten glaze essentially solving the issue entirely in this case I'm quenching in water so the glaze mostly fractures off if quenching in oil the glaze can be removed by briefly soaking in hot water [Music] once tempered the spring is now set and can be safely removed from the forming [Music] recess [Music] [Music] from here the Springs can be polished or perhaps blued as [Music] required [Music] [Music] okay so that's the basic idea of this sort of carbon spring formation produce the raw stock to the required Dimension form it to shape and then heat treat with the spring size scaling according to wire size the number of strands led into the recess and the recess size itself of course the shape of the spring can be quite different to the standard flat spiral that we've just seen for example this helical shape is the standard for the Marine chronometer so let's have a quick look at that the former for the spring is as you'd expect effect in the shape of the final spring the process to make it is much like single point threading except the cutting tool cuts a flat just slightly wider than the spring stock and the cut depth is around half the spring thickness one thing worth mentioning is that the Fasteners at each end of the helical former are required to be left-hand thread to make sure that the spring material is under a light tension on the former as the Fasteners are closed down from here the process then follows the familiar pattern of heat treatment and here's a closer look at just how brittle the spring material is immediately after the quench tempering transforms that material making it not only set its shape but also changing its metallurgical properties to be what require for a [Music] spring as shown previously from here the spring can be taken to a high polish or perhaps heat blued as required now while we're here there are several other interesting spring shapes to be found in horology the spherical spring being one of my favorites despite its exotic shape the process for making it is mostly the same as the previous examples the wire stock is brought to the required Dimension and then wound around a former that'll Define the shape of the spring once it's set in this case to a spherical shape the heat treat and tempering are the same the any real difference in this case is the former itself it's made from thin sections that are removed through the coils of the spring at the end of the process piece by [Music] piece [Music] I mentioned earlier that carbon steel balance Springs were superseded by alloy Springs long ago and are now almost exclusively found within antique devices but wherever they appear especially when heat blued they're often the standout element of a mechanism thanks for watching I'll see you later [Music] a

Channel: Clickspring

Views: 273,165

Keywords: watchmaking

Id: in6yWrlighI

Length: 19min 13sec (1153 seconds)

Published: Sun Feb 25 2024