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39 tooth splines?

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  • #31
    Hmmm - this too?


    I was very impressed that analysis in a practical environment that you just posted.

    Your previous very good advise about the increasing accuracy of a dividing plate still holds true as well.

    A couple of additional or supplementary points if I may.

    There is some "clearance/s" in the indexing arm spring-loaded plunger that may add to the problem. I checked the holes in my indexing plates as well as the plunger end/spigot that engages it. The plunger has a locating taper which engages the counter-sinks in the mating plates, so I guess that will help.

    I don't know why it happens, but a lot of people just will not clamp the rotary table after positioning it. There is both back-lash between the worm and the wheel as well as end-play in the worm spindle - all of which "add up" and which will contribute to or cause unnecessary error and so "bite you in the ar$e". "Hobbing" is potentailly fraught with this problem.


    • #32
      Originally posted by oldtiffie
      I guess you mean in "quick indexing" mode. My 8" "Vertex" QI rotary table had that built-in but as I think you suggest, it has a 24-slot "Master" QI plate "built-in" with masking plates which can over-lay it for number divisible into 24.

      I hadn't thought more of it until I read your post. I guess as a concept it might be possible to make and use a 39-slot indexing plate. They are pretty accurate. I would really need to open up the base of the QI and check to see it it was even possible or practical.
      My original question (along those lines) was why the earlier poster said it couldn't be done with a rotab. Which of course, it can, particularly using the Vernier feature to split degrees. Then there is the simple indexing head like my Hartford. Often called a "spacer" (rather than Super Spacer), it has no feature for incremental degree selection but rather is limited strictly to the index plate. Most commonly 24 divisions, but I've also seen 25, 18, and 36 division plates along with many masks for factors. But these, without a correct plate (in this case, strictly requiring a 39 notch plate) simply can not do the job. What you call "quick indexing mode" is the ONLY mode. Then there is the hybrid Super Spacer which incorporates both the rotab worm drive AND direct indexing, often with options for both dividing plates AND even axial angular settings like a Universal Dividing Head. While heavy and bulky, particularly in the axial angle adjusting models, they are surely the most flexible of all, particularly when combined with the dividing plate adapter. Sadly, I don't yet posses one, though I really have found no particular needs beyond my various indexers and rotary tables.

      Not sure how universal these terms are, but they are accurate to the best of my knowledge, at least by US (or regional?) usage...
      Master Floor Sweeper