Thank you so much Dean. Teaching with your large, printed model, and the example you used in part 1 has helped me tremendously. I really appreciate you.
Great 😃👍 video, excellent example of real world assembly for the students to learn from. I really enjoy your videos, thanks for taking the time and teaching us your knowledge.
Thanks so much! I feel like there is very little printed or online information on this topic, I am working on more videos to address the design process.
I have comment about the datums on red part. Based on its fit and function, we could use one of the side surfaces as datum A and control the perpendicularity of threaded holes and the parallelism of the opposing sliding surface within 0.5 or something (I'm metric btw). Datum B can be largest surface with a generous profile tolerance. Datum C could be the top surface to control the orientation of the threaded holes back to all three datums. Although datum C is mating to air, as its controlling the orientation of the hole - it should have profile of 1 for proper hole alignment.
First off, I absolutely love your videos. I am a mechanical design engineer with ~8 years work experience in consumer products, but having always worked with Asian suppliers, I never really learned GD&T. I am working in automotive now and your videos are the best I've seen for understanding the theory of GD&T. Let's see, I'll do my best here. For the custom Thumb screw I would make the running surface as Datum A and keep Datum B the same, but that's just because I don't know enough to make a thread as a Datum. To me that would just be easier to inspect. Then for the Red Part I would say you do favor one side over the other in that the thumb screw squishes one face into the inside of the Yellow Part, so that should be your primary datum. Then maybe the hole for the custom shoulder screw should be the second datum since it's critical that the hole on the other side is concentric with that (maybe change the design so that it's a thru hole that gets tapped on both sides to ensure that that is the case). Then the last datum can be the surface you selected as A, it would be just one point that stops the rotation. From a design perspective one issue I see with this is that you're constraining the micrometer with the end of the thumb screw, which is a small circular surface and is liable to allow the mic to rotate. I think there's a way to keep the same number of parts but make it clamp like the mic holder you showed at the beginning.
Dean, this should be the series intro. It is incredibility enlightening for sapcial learners, and I would argue any type of learner. The video stands on it's own, but if it existed in an edit form with intro level imagery tie-ins and concept phrases it would be a smash. Text book in a minute if you ask me. Might as well download the concepts.
Thank you very much for this example. Do you have a presentation similar to this for using alignment pins on two mating components. Thank you for the GREAT WORK !
Hi Dean, great video I've always avoided using threaded holes as datums due to the difficulty of picking up on them with a CMM, and unfortunately this has often sacrificed the functionality of my GD&T Do you have any videos on using threaded features as datums and inspection for threaded feature positions?
Thanks a lot for your videos! Very well done! I have a question: on the drawing relating to this video on "item 4&5" there is a total runout indication. It relates to datums A and B. Is it datum B really necessary? I remember that in your video "Lesson 5: runout tolerances" you said that only the axis datum is really needed for runout and total runout. Am I wrong? Again thank you for your effort!
Hi, thanks for the great input! You are 100% correct. There is really no need for datum B on that runout callout. It’s a habit for me to put that on a drawing, the notion is that I want the inspector to recognize that it is the same DRF as the position tolerances, but at inspection making one point of contact to datum B to check runout is superfluous.
Dean, I just finished my studies about GD&T application I fell confident in reading an drawing and interpreting it tolerances. I also know how different geometric tolerances controls the permissible errors and how it effects the parts. Although something I don’t fell confident is estimating the tolerance zone values. I know it depends on which function of each part and how it assembles but I don’t know how think in order to estimate a good tolerance value for an part. Do you know any book or references which covers examples on how to estimates this values?
Hello , Thanks for the great way of explaining what sometimes can be very confusing. You have been my best instructor. I have a question: Can you please walk through a 3d Best Fit alignment? I would really appreciate that!
Thanks Dean! Question about thru-holes with counterbores (or csinks). When you select a thru-hole and cbore pattern (or even a single instance) as a datum, how would an inspector build out the Datum Reference Frame for it since they are two different/separate features?
Hi, Great question without an easy answer. Let me think about the long answer a little bit. The short answer is that the inspector will likely take the diameter with the most surface area and base the datum axis on that feature, probably the hole instead of the counterbore. If you have an example, feel free to email it to me and I can take a look.
Hey bud. Thanks for all the hard work. Can you please answer a question for me? Can you have basic dimensions as a datum or do you have to have an actual feature to use as a datum.
Thank you for the video I have a bit of a concern to locate the holes in a contour surface. I.e, the drilled holes in the contour surface must always be perpendicular to the curved surface. Could you please help me in understanding how to define this criteria ? Can the curved surface be a datum ? Is it possible to use an evolutive curved surface as a datum ?
Hi Dean. After watching a bunch of your great videos, I am still a little unclear on how it works when you choose a hole (or hole pattern) as a datum feature. For the blue base part, when you say that you are choosing the two holes as the datum features, does that mean that the center axis of each hole is a datum feature? Or because there are two holes, is it the center plane between the two holes? If it were a hole pattern with multiple holes, would it be the center axis of the pattern?
When choosing two holes as a datum feature, each hole has a datum axis and these axes establish a datum plane. If you have Y14.5 at hand, look at Figure 7-6 (2018 edition). If you have 4 holes for example and make it a datum feature, the 4 holes establis a datum system like in Figure 7-18. A pair of datum axes establishes a datum plane, and these theoretical datum planes have a derived median plane which would be the secondary and tertiary datum reference planes. If you have a cylindrical part and a hole pattern around a circle, the true geometric counterpart would be either an inscribed or circumscribed circle, and the datum axis would be the axis of the true geometric counterpart.
