Hi Kirk, One of the main reasons I want to try to generate gears and, particularly, pinions is the great problem I have in trying to make working pinion cutters small enough for the watches I work on. I could get cutters made but, as you have said, a different one is required for each individual pinion or small subset of wheels and, at a cost of 50+UKP ($100) each, any repair using more than one of them would probably become uneconomic. This is compounded by the fact that most of the watches I work on are more than 200 years old and their wheels and pinions were hand cut or made with 'home-made' cutters which do not comply to any current standards. So, if the watch is to run properly, I have to try to match the size and shape of the original teeth exactly and no currently obtainable commercial cutter has exactly the same form as these old wheels and pinions. Consequently, even where I have a cutter which is very close to size, I usually end up having to hand finish the profile of each tooth by filing and polishing - a very tedious and lengthy process. :-(
My wheels and pinions are cycloidal and not involute and have radial flanks to the leaves with a rounded or ogival top so that, in my case, the cutting can be in two stages - the straight radial flanks and the rounded tops. However, I think that the basic process should be the same whatever the tooth profile - maybe mine would just need an additional step to move the cutter a bit in Y before starting the rounded tops to the leaves whereas an involute would need the curve generated from the start. The big problem making a cutter is all down to the size and the difficulty in measuring and working to exact tiny dimensions. The 5-leaf pinion I need to make at the moment has a flat in the bottom of the tooth spaces of just 0.2mm width and a tooth depth of 0.45mm or thereabouts. Have you ever tried to get accurate measurements across sloping faces at this scale?? ;-) I have used my little cnc miller to successfully make cutters but it usually takes a couple of goes at least and it is a problem to get relief on the cutting edges. My idea for generating the pinions - (which are one-offs and not multi productions, therefore the time involved in making them is of no consequence) - is to use tiny grinding disks like the thin cut-off disks they sell for Dremels but thinner ( dentists use ones of 0.2mm thickness ) and grind the blank to shape. I have used this technique to grind small shafts and it works fine provided the speed of the disk is high and the feed is slow. I was actually very surprised how well the disks worked and after half an hour's grinding, the disk was still virtually the same size as when I started. So, if I can just work out the way to compose a G-code file with the multiple loops, I think the idea is well worth a try. Maybe for your purposes, you could consider using a similar idea by finding a supply of larger grinding disks - angle grinder cut-off disks maybe? -- Best wishes, Ian ____________ Ian W. Wright Sheffield UK "The difference between theory and practice is much smaller in theory than in practice..." -- Best wishes, Ian ____________ Ian W. Wright Sheffield UK "The difference between theory and practice is much smaller in theory than in practice..." ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
