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Need help reporting Taper/foot of a Cone

Hey guys. I am inspecting a part with a tapered bore. The drawing calls out '1.5" PER FOOT TAPER' with a tolerance block tolerance of ±.010. I measured the feature as a cone and my options are to report as an angle or half angle. I know that the half angle should be 3.5763. And to translate that to taper per foot I worked out the following equation: taper/foot = 24*tan(half angle). How can I implement this so that my report shows the measured taper/foot with a nominal of 1.500 ±.010? Currently I am reporting the half angle with a tolerance of ±.0238 which is what I calculated as .010"/foot taper as a half angle. Appreciate the help. 

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  • Respectfully, i feel that note is not a feature of size controlled to the block tolerance.

    No matter how you slice or dice a ~1.5" long axis line... Multiplying or compounding 1/10th of the measured value, to equate to a repeatable result that will discern a ±0.010 tolerance is an impossible ask.  You are multiplying your uncertainty of cone angle to equivalate it to that 1.5" along a 12" ratio.  Cone angle is very difficult to control on a cmm.

    The engineer either needs to change the spec to tolerance it as an angle form centerline as you are doing ± a relevant angular allowance or go back to school.

    Another consideration, the print has that "Bore diameter | Tapered +0.002/-0.000" 
    --Is that the intended "TAPERED" cone tolerance?  

    If so, construct a 1.5" taper along a 12" line angle, at the nominal bore diameter (consider it as a BASIC value).  measure t values from that line.  Tolerance the t-values as +0.001 / -0.000 (radius of the diametrical tol) repeat radially like 4 times about a few spots down the tapered bore

  • It does feel odd applying the block tolerance to a dimension in a note, but I think it is the most reasonable conclusion. I believe that the 'bore Ø tapered +.002/-.000" tolerance applies to the 1.000 dimension at the big end of the taper which is toleranced similarly on the side view. Since the small end of the taper is only reference the tolerance has to be applied to the taper itself. This is simply my conclusion as a new engineer with limited experience.

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  • It does feel odd applying the block tolerance to a dimension in a note, but I think it is the most reasonable conclusion. I believe that the 'bore Ø tapered +.002/-.000" tolerance applies to the 1.000 dimension at the big end of the taper which is toleranced similarly on the side view. Since the small end of the taper is only reference the tolerance has to be applied to the taper itself. This is simply my conclusion as a new engineer with limited experience.

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