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  1. AMontembeault

    Tapered Datums

    Derp! Got it, thanks!
  2. AMontembeault

    Tapered Datums

    Y14.5 specifies the use of a conical taper as a datum candidate, arresting 5 degrees of freedom - 3 translational, 2 rotational. It makes me wonder, why couldn't the same apply to a wedge shaped, extruded feature - a dovetail, for example. Such a feature would also constrain 5 degrees of...
  3. AMontembeault

    Profile of contour

    Hm, sort of. I want the depth of my groove to shift with the change in diameter, rather than fixing it to the axis of the cylinder.
  4. AMontembeault

    Profile of contour

    I have a cylinder (actually a "pipe"), from which I establish datum "A" as the axis of the OD of the cylinder, datum B as an end of the cylinder, and datum C from a hole drilled into the side of the cylinder. On the OD of the cylinder, I have to machine a grooved contour, one that presents...
  5. AMontembeault

    Profile on a unit basis

    ASME Y14.5 - 2009 specified in section 8.3.3.2 that profile could be specified on a unit basis (as a note to the section). In the 2018 version of the standard, this reference has been omitted from the comparable section and there is seemingly no reference permitting profile on a unit basis...
  6. AMontembeault

    Multiple Single Segment Positional Tol and Datums

    Got a bit of an oddball question I have a series of different sized features for which it would be beneficial to control via multiple single segment positional tolerances. It has been proposed to turn one of those holes into a datum reference for controlling one or more other holes, also with a...
  7. AMontembeault

    3D PMI What is the future and or are 2d drawings going away like the drafting board?

    Autodesk Inventor, which can be equipped with a 1-D tolerance analysis tool that largely relies on model based definition for WC and RSS outputs, but we mostly use 3DCS Multi-CAD for monte carlo based 3-D analysis.
  8. AMontembeault

    3D PMI What is the future and or are 2d drawings going away like the drafting board?

    I can only speak anecdotally, but the department I work for has had some pretty good success with transitioning to a hybrid of 3D PDF and traditional 2D drawings, with an eye towards eventually going to just 3D PDF's in the future. For us, MBA doesn't take any more time than traditional...
  9. AMontembeault

    Assembly level dimensioning

    Having a bit of a philosophical debate at work, and I was curious what a broader community might think. ASME Y14.5-2018 Section 4.1 (p) states "Dimensions and tolerances apply only at the drawing level where they are specified. A dimension specified for a given feature on one level of drawing...
  10. AMontembeault

    Thin Datum Surfaces

    I should perhaps be more specific. The B datum is the median plane derived from the width of the part.
  11. AMontembeault

    Thin Datum Surfaces

    I have a sheet metal part, which is more or less square, with a bilaterally symmetric, sinusoidal contour cut on one side. I set my primary datum "A" at the large planar surface of the part, secondary datum "B" as the midplane of the part, and tertiary datum "C" as the edge opposite my contour...
  12. AMontembeault

    Datum Translation application

    Here is a simplified sketch: In this design, DIM 2 and DIM 3 are somewhat critical for fit-up. The part is also too massive to be accurately measured with an arm based CMM. In older days, I would have just used limit dimensioning on DIM 2 AND 3, but I'm trying to be consistent with ASME Y14.5...
  13. AMontembeault

    Datum Translation application

    Can a datum translation modifier be used when the datum is a planar surface? I can't see anything in the standard which seems to explicitly prohibit this, but every example out there I can find typically only demonstrates this concept using a datum derived from a feature of size (typically a...
  14. AMontembeault

    Surface Profile and Size

    OK, so expanding on the idea then, if the dimension isn't called out as a diameter, but as a radius instead, and that profile isn't over the entire surface, but on a unit basis (for example, a note saying that the profile applies in any 45 degree segment, should the radius be basic? Can we say...
  15. AMontembeault

    Surface Profile and Size

    I'm looking at a series of prints which detail a round feature of size, controlled by a datum-less surface profile. My question is, should the diameter be basic, or limit toleranced? My inclination is that it should not be basic - that a datum-less surface profile is just a form control (in...
  16. AMontembeault

    Profile without Datum reference

    The old prints I'm working with specify "Any 45 degree segment", which is problematic because there are an infinite number of 45 degree segments.
  17. AMontembeault

    Profile without Datum reference

    Referencing this thread: https://www.eng-tips.com/viewthread.cfm?qid=314750 It was discussed that a surface profile without a datum would essentially just be a form control on a singular surface. However, based on that discussion, I believe, based on the context of those discussions, that's...
  18. AMontembeault

    GD&T for small features/non-features

    I have a number of parts for which vendors supply scribe lines on surfaces, used for the purposes of alignment at the assembly level. These scribe lines are typically called out as having a maximum depth and width, but could be produced with no discernable dimensions (for example, a scribe line...
  19. AMontembeault

    Design Best Practices - Rolled Cylinder

    I have a rolled, right cylinder, approximately a meter in diameter (inside) and 1.5 meters in length,with a wall thickness of about half an inch. The problems with dimensioning this are: 1) its not really rigid in the free state 2) To constrain it adequately, on a mandrel, for example, would...
  20. AMontembeault

    GD&T Interpretation - Perpendicularity and Limits of Size

    I reccently had to check a drawing of a right cylinder, with a length tolerance of +/-1 and a perpendicularity requirement on each flat end of 1.5 with respect to the axis (Datum A). I rejected the drawing, on the basis that if each end has 1.5 perpendicularity at the same time, then rule 1 is...

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