What are the uses for an ultradex?
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  1. #1
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    Default What are the uses for an ultradex?

    i.e., is an ultradex used only for calibration purposes, part checking and optics, or is it intended to be used as a rotary table for machining? Or does the answer depend on the model?

    I have a 5" one (not sure what brand it is, so I am using ultradex in the generic sense for a serrated tooth divider). It is really nice to use, easy to change settings, but I don't think it is intended for machining. More likely it is intended to be used as an inspection stage for an optical comparator, or similar. Here are some photos with the ultradex and a bottom from another:

    img_1120.jpg


    img_1121.jpg


    img_1122.jpg


    What is the purpose of the metal bracket on the side of the ultradex in the photo above?

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    Pretty sure those are extremely high accuracy and intended mainly for reference, set up and inspection- more of a metrology tool than a machining fixture. Probably suitable for light grinding if that level of accuracy is required.

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    The downside is that, unless it's a compound one, you are "limited" to a specific number of very precise divisions, perhaps one each full degree (gear with 360 teeth).

    With a compound one and gear sectors (e.g. Newbould indexer) you could obtain extremely fine and accurate divisions.

    Paolo

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    My guess is that the bracket is a part of a base-rotation mechanism that allows the position of a table-mounted object to be "zeroed" fairly easily before using the Hirth coupling to divide the circle into aliquot parts.

    I would further guess that the base pivot is probably coaxial with the table pivot, and the bracket arm is pushed back-and-forth by 1) opposing tangent screws OR 2) a tanget-screw-and-opposing-spring mechanism that bears against the cylindrical segment at the outer end of bracket.

    Such a devise is built into Brunson Instrument Company's collimator test stand, used to test and adjust surveying and optical tooling instruments.

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    Pardon my ignorance, but where did the term "ultradex" come from? Inspection had a few, they called them Becker plates, perhaps a brand, and they were made to work horizontally or vertically.

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    To the best of my knowledge, Ultradex was the AA Gage tradename for a very precise rotary indexer that used a pair of face gears to divide the circle into aliquot parts. Face-gear couplings have been made in two main flavors; the Hirth coupling uses straight-flank radial teeth, and the Gleason "Curvic" coupling uses radial teeth having convex / concave flanks.

    These face-gear couplings are almost the antithesis of a kinematic coupling, in that they work on the basis of "elastic averaging" in a deliberately-overconstrained, very precise, slightly flexible, interface that can be mated in as many different positions as there are teeth on the mating interface.

    My first experience with an Ultradex table was 40 years ago, and the table itself was decades old at the time. It had a 360-tooth pair of face gears, providing 1-degree +/- 1/2 arcsecond indexing increments. An angle generated by indexing the table to two different positions would therefore have a maximum error magnitude of 1 arcsecond. A later generation Ultradex offered single-position indexing within 1/4 arcsecond magnitude.

    The original Hirth and Curvic couplings required raising the table itself off its base to de-couple the coupling. A non-rising variant was developed later, based on 3 face gears. Two of the face gears are concentric. One is fixed to the inside of the base, surrounding a second that is fixed to the underside of the platen. These two face gears do not contact each other.

    The third face gear is mounted on a rise-and-fall mechanism inside the base so that, when raised, it engages both the inner and outer gears of the concentric pair.

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    Very nice. I could have used one many times in grinding.

    Accurate index for 1,2,3,4,5,6,8,9,10,12,15,18,20,24,30,36.40,45,60,9 0,120, 180,360 spaces/divisions..

    Ultradex Rotary Tables - MK II & III by A. G. Davis - AA Gage in Detroit, Michigan area


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