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  1. #1
    berger is offline Aluminum
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    Default how to measure cone angles

    what is the proper way to measure cone angles male and female,with your basic hand measuring devices. thanks.

  2. #2
    John in CA is offline Hot Rolled
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    For a full male cone, coming to a point, I'd measure the diameter at the base and the length, and trig it out. For a section of a cone ( two flat ends), for a rough check I'd measure the difference between the two diameters and the length, and trig it out. For a finer measurement, I'd set the cone on a sine bar, backed against a couple of stop pins or a fence, and increase the length of the gage block stackup until, when I swept the horizon of the cone at both ends, my .0001" DTI got the same reading. The length of the stackup, multiplied by the center-to-center distance of the rolls on the sine bar, would equal the sine of the included angle of the cone.

    The sine bar procedure would be one way I could think of to get a good, direct quantification of the angle of a female cone. Usually when I need to cut a female cone section, it's a machine taper socket like a Jacobs, and when I do that I don't actually look for direct measurements because I'm fitting it to a known master, using Dykem to get a witness until I have the fit I want. But if I really needed to quantify the angle, another way I could think to do it would be to put the part in a vise on my mill, and a DTI in the spindle. Care would need to be taken to see that the axis of the cone was perpendicular to the table. Then I'd use the DTI to pick up the horizon of the cone at the open end, and move the spindle down ( or the knee up, as the case may be) a known amount, taking note of the movement on the indicator needle. Then I'd have a change in radius and a length that I could use to trig half the included angle.

    Be aware, though that doing it that way contains some sources of error and would probably be frowned upon. For one, the angle of the indicator arm relative to the bore has an effect when taking direct measurements. My Interrapids are set so that an angle of 12* relative to the surface being measured gives a 1:1 reading. Might not be the same for all indicators, though,

    Hope this helps,

    John

    "I'd rather be lucky than good any day. "

  3. #3
    peterve's Avatar
    peterve is online now Titanium
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    If you only need the angle measure at 2 different diameters a known distance apart and do the trig You get the best result when that distance is as big as possible
    For inner cones with a flat and square surface you can use one of these

    http://www.schut.com/catalog/en/en_0213.html

    If you use a short and a long measuring arm you have all what you need quit acurit
    You can also trig/calculate the ID on both the ends of the cone because you have the ID of a known distance from the top
    A very versatile instrument BTW

    Peter from Holland

  4. #4
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    Pazuzu71 is offline Hot Rolled
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    For a Female cone we use 2 ball bearings of different diameters, dropped in the hole.
    Then trig the angle, depth of balls, etc.
    it's pretty simple once you have it all drawn out.

  5. #5
    Troup is offline Titanium
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    I do what Pazuzu said except I use bearing balls, not ball bearings

    and a depth mike .... but the depth rod on a vernier is almost as good

  6. #6
    randyc is online now Stainless
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    Quote Originally Posted by Pazuzu71 View Post
    For a Female cone we use 2 ball bearings of different diameters, dropped in the hole.
    Then trig the angle, depth of balls, etc.
    it's pretty simple once you have it all drawn out.
    that's a neat tip, thanks ---
    randyc

  7. #7
    randyc is online now Stainless
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    Quote Originally Posted by The real Leigh View Post
    Yes, the ball idea sounds good, but there's a subtlety that must be addressed.

    The circle of contact between the ball and the cone is not at the horizontal center line of the ball (assuming the cone is standing on its apex).

    Contact exists on a plane defined by the points of tangency between the two surfaces, which will be below the center line.

    Since determining that location exactly requires knowledge of the angle of the conical surface, and that's the parameter being measured, you have a circular relationship which cannot be simply solved.

    - Leigh
    Yes, you're right. One more piece of information is needed (the major diameter or minor diameter of the cone for example) before we can close the deal.

  8. #8
    Troup is offline Titanium
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    I'm not sure where Leigh's post went, it only appears quoted on my (Firefox) session

    It can simply be solved, if you have access to a parametric CAD package

  9. #9
    9100's Avatar
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    This isn't original with me- someone posted a version of this somewhere back there. Mount a disk on the end of a threaded rod and a larger one with a threaded hub up the rod. Slide the rod into the cone until it seats on the smaller one, then screw the larger one down to seat it. Measure the distance between them. Calculate the angle, or if you are really lazy, draw it in Autocad and read the angle. This eliminates the error with balls.

    What would be really cool would be a long stroke dial indicator with the smaller disk on the rod and the larger one on the body. Just shove it in the cone and read.

    Bill

  10. #10
    randyc is online now Stainless
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    Quote Originally Posted by Troup View Post
    I'm not sure where Leigh's post went, it only appears quoted on my (Firefox) session

    It can simply be solved, if you have access to a parametric CAD package
    Of course, since tangential snaps are so easily performed. It's been my experience, in fact, that a complete graphic solution takes less time for me than just setting up a model to solve by trigonometric means. (And perhaps with less chance of error.) Thanks, AutoCAD !

  11. #11
    9100's Avatar
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    [QUOTE=Troup;1208008]I'm not sure where Leigh's post went, it only appears quoted on my (Firefox) session/QUOTE]
    Is Cuda on line with some new software?

  12. #12
    John in CA is offline Hot Rolled
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    I'll definitely remember the ball trick, because even if it can't be used to directly measure the angle of the bore taper, it still makes a good "yes/no" check. You could trig out the depths that a ball of a given diameter "should" drop, at the high and low limits of the angularity tolerance
    (and, as pointed out, one known diameter and depth) and use the depth mic to verify.

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