Hi Dave, I haven't checked the wheel for accuracy but I would think that this method of generation actually is less prone to errors than methods which cut each tooth separately. Once the teeth are established as to number and you infeed the wheel onto the tap, there are always at least 3 cutting teeth (threads) in contact with the wheel at any one time and this should even out the effects of any minor errors in the tap pitch. I also usually feed the worm along the tap a little each way as I cut which will again reduce errors by using different parts of the tap. I don't know whether there would be any benefit in reducing cyclic errors by producing only wheels with an odd number of teeth like 91 instead of 90 - I did work out what the error would be if I could only make a 91 tooth one and set EMC2 up to suit it and, from what I remember, the error was infinitessimal. The great beauty of this method is that you can make a wheel from scratch in just a few minutes. I simply set up a post with the same diameter as the bore of the blank on my miller's bed ( actually made as a tube sleeve over a bolt ), slipped a spacer onto it ( a second wheel blank) and then the wheel blank I wanted to cut and capped it off with a nut and washer to stop the blank lifting during cutting. The cutter was a normal 10mm x 1mm tap and, with the blank initially set to centre height of the cutter, I wound the blank into the cutter so as to take a fairly hefty cut as I found that this was the easiest way to establish a set of even teeth ( i.e. not 90 1/2!). Then I just left the thing running merrily along as I slowly wound the blank further in until I thought that the teeth in the wheel were deep enough - i.e. not quite full depth on the tap so that I didn't get 'bottoming' when using the finished worm. Once this stage was reached I decided that I wanted the teeth to be 'flat' across the wheel so that I could remove it from the rotary without having to disturb the worm ( don't know why but it just seemed like a good idea at the time...) and so I then wound the knee of the machine up and down slowly as the work was still spinning away. On other wheels I have made (which I made on the lathe) I didn't do this and so the worm and wheel make contact for maybe 1/3 of the worm's diameter - this may be better - I don't know. Anyway, the whole cutting job and subsequent cleaning up took only about 5 minutes per wheel. The other thing I did was to mount the wheel on an eccentric in the rotary table so that I can easily adjust backlash if necessary to compensate for wear - that hasn't been necessary yet..
Why not make one and try out this way - it costs nothing except a bit of scrap material and maybe half an hour.... Best wishes, Ian ______________________ Ian W. Wright Sheffield UK Dave Caroline wrote: > Looks nice Ian but I would love to measure the wheel for errors in > tooth to tooth distance. We had trouble directly attributable to the > worm and wheel in a bought dividing head, we made some 144 tooth > wheels for a project at the BHI and they were rightly rejected, for > normal clock work the error did not show or was withing tolerance but > for a high count the error becomes pronounced. > > The easy check I use to test dividing now is get your digital > calipers, measure over n teeth, zero caliper , rinse repeat but only > zero if less than a previous measurement. you then see a large > percentage change in places around the wheel if you have a dividing > error its due to worm/wheel form error giving a sawtooth error to the > dividing. > > Dave Caroline > > ------------------------------------------------------------------------------ > Download Intel® Parallel Studio Eval > Try the new software tools for yourself. Speed compiling, find bugs > proactively, and fine-tune applications for parallel performance. > See why Intel Parallel Studio got high marks during beta. > http://p.sf.net/sfu/intel-sw-dev > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.733 / Virus Database: 271.1.1/2725 - Release Date: 03/05/10 > 19:34:00 > > ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
