As someone with practical experience of trying to use cnc to make watch parts in my capacity as restorer and repairer of antique chronometers and complicated watches I can say that its usefulness is very limited. I built a small cnc mill with the express purpose of using it to help me make some of the parts I need to replace in the antique watches I work on but it has really seen comparatively little use for this purpose. I trained myself over the years to use the methods and tricks of the old time watchmakers from the time before electricity and modern materials and I honestly find these methods much quicker than trying to use cnc for one-off parts.
I have cut (gear) wheels down to less than 1/8" diameter with up to 20 teeth on the cnc machine (see album at https://picasaweb.google.com/114833214086356299537/WatchParts?authuser=0&authkey=Gv1sRgCJLN-tn5hPeEzwE&feat=directlink - these wheels are sitting on a British 5 pence coin which is a little over 1/2 inch diameter) but, while the machine did the automatic dividing and cutting, I still had to make the means of holding the wheel blanks and the cutters etc. which took as long as if I had just cut them on the watch lathe with a simple division plate (2nd photo). I originally thought that cnc would be an easy way of making some of the flat parts for the striking and repeating work on the watches but that proved to be a failure. Whilst I can draw or design the missing or broken parts in a CAD program - in Rhino, for example, I can use a photograph of the watch mechanism suitably scaled as a background and actually draw the new part as if it were in the watch (3rd photo), translating that into metal on the cnc machine is often impossible. Much of the 'flatwork' needs sharp internal corners such as in racks (several of the other photos) and this is impossible to produce with rotary tools such as endmills. The sizes involved are just too small to be able to find or make a small enough endmill which is also robust enough to cut tool steel (say 8 or 10 thou diameter). Consequently, any attempt to mill out the perimeter of such a part would end up as just a series of blunt indentations which would not even be good enough to give the accurate location of the working edges. The other big problem is in holding the work. The last 3 pictures show various staffs which I have had to make for watches. The little one which is less than the width of the pinhead (normal dressmaking pin) was for a wheel in the striking work of a small dress pocket watch from about 1728 - how would you hold that to machine it in a cnc machine? The next is a couple of cylinder watch balance staffs which are polished steel tubes with end plugs for the pivots and about 3/4 of the tube wall cut away at the opening. The last picture is rather a rarity, thank goodness, and is the balance staff from a very high class, French, 'ruby' cylinder watch dated about 1730 although this 'ruby' is actually pale sapphire. The end pivots on this were badly bent and couldn't be repaired and so I had to make a complete new staff - it took many attempts over about 3 weeks before I got a good one!!! The staff is a hollow steel tube which is used as a cage to hold the 'working part' near the wheel which is a cylinder of sapphire about 1mm diameter and 0.7mm bore with almost half its diameter cut away and the cut edges polished to a defined profile. The original was cracked and it took a lot of thought, trial and error before I managed to find a way to make and polish a new one!! The bottom part of the staff is also cut away for about 80% of its diameter. So come on Jon, how would you make these on your Bridgeport ;-) Having said that, if you are prepared to put in the hours necessary to design the parts, make the wheel cutters and the jigs necessary to hold the parts while they are being machined, you probably could make 70% of the parts for a very basic watch by cnc - they would still need hours of fitting and finishing and there would be parts that you just couldn't make but it would provide a lengthy distraction from other things and you would be able to make hundreds of the same parts. For myself, I'll just carry on making the parts simply, by hand methods as, for one-offs, I know it is the quickest way.. In the watch industry now, most of the parts other than the main plates are made by wire erosion or by photo etching and the design of parts has been adjusted to suit these methods. Best wishes, Ian _____________________ Ian W. Wright Sheffield UK ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.1872 / Virus Database: 2092/4621 - Release Date: 11/16/11 ------------------------------------------------------------------------------ All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
