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<\/a><\/figure>\n\n\n\nI also made an arbour to hold my gear blanks. I made this primarily because the largest brass bar that I have which is 19mm diameter and is just the right size for a 36-tooth Mod 0.5 gear. I only had approx. 200mm\/8 inches, so I wanted as little waste as I could get away with to make best use of it.<\/p>\n\n\n\n
The arbor has a short section at 3\/16 and then the end is threaded M4 for a locking nut.<\/p>\n\n\n\n With it made I then cut a 36-tooth gear.<\/p>\n\n\n\n After some off line discussion with a fellow member of Western Thunder and much grinding of my cutting tool, I finally managed to get a 20 degrees tool with sufficient support underneath the point and was able to cut a \u2018proper\u2019 worm to suit my mod 0.5 gear. On Susie\u2019s advice I wound the lathe over by hand rather than under power to cut the worm. Now I don\u2019t have any kind of \u2018handle\u2019 to allow me to turn the lathe over smoothly (I have seen other machinists who make an expanding arbor for their lathe spindle to allow smooth hand cranking) so my effort using the holes in the collet chuck and a tommy bar were quite laborious but I got it done.<\/p>\n\n\n\n I also had another go at making a gear but with a slight angle to the teeth to better mesh with the worm.<\/p>\n\n\n\n My method of creating an angle on the teeth is very unscientific, I started off by adding a length of 0.7mm nickel rod under the front end of the spin indexer to raise it up and it did work albeit not enough and I also forgot to raise the cutter height so I ended up with slightly lopsided teeth and the angle wasn\u2019t quite enough.<\/p>\n\n\n\n Undeterred, I increased the rod size to 1mm and tried again. It was at this point that my learning experience went into overdrive. According to the charts that I have been using* the cutting depth for Mod 0.5 is 1mm thinking I was being clever I increased that by 0.1mm. As soon as I made the first pass, I realised that something was wrong. The cutter had not only cut the tooth but it had also created a much wider channel in the blank which you can see on the right-hand side of my hacked about blank below.<\/p>\n\n\n\n The rest of the teeth on the damaged blank were created by my testing of various cutting depths to determine the point where the cutter cut the tooth without removing any from what would become the adjacent tooth and thus reducing the overall diameter of the gear. After a few test cuts, I determined that for my cutters 0.8mm was the maximum depth before it effectively reduced the height of the adjacent tooth.<\/p>\n\n\n\n *Bob did point out earlier in the discussion that the charts were actually for the cutting of worms rather than gears but we determined that in the absence of any other data that they were near enough for both.<\/p>\n\n\n\n For the Mod 0.3 the data from the chart worked fine and now that I know I can refine my own version based on what I have determined. No doubt that if I do buy a set of Mod 0.4 cutters in the future, I will have to do some tests to refine the Mod 0.4 data to suit the practical application with my set up.<\/p>\n\n\n\n Once I had made that discovery, I cut another gear and although it was successful, it still wasn\u2019t angled enough so I will do further experiments on my duff blank to see how a 1.6mm lift works, before committing to another full gear cut.<\/p>\n\n\n\n Finally, to round off this war and peace update I also cut another worm with the 20 degrees tool in a piece of free cutting mild steel (the others were cut in recycled printer bars) under power and I think that it\u2019s a much nicer worm albeit that there isn\u2019t much visible difference from the \u2018hand powered\u2019 example.<\/p>\n\n\n\n This week has been very much about more learning. First of all, although I reground the 20 degrees cutting tool, I had still left too much of an undercut and the point snapped off again after about five passes. I … Continue reading <\/a><\/figure>\n\n\n\n<\/a><\/figure>\n\n\n\n<\/a><\/a><\/figure>\n\n\n\n<\/a><\/figure>\n\n\n\n<\/a><\/a><\/figure>\n\n\n\n<\/a><\/figure>\n","protected":false},"excerpt":{"rendered":"