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  1. supergee

    Is there a preferred true position standard?

    I COMPLETELY agree with you! I have relagated the teaching of symbology to youtube video so I can concentrate my class on THINKING. My student told be yesterday that GD&T is fun ?!?! because they need to think a lot. they need to fill a form for each fearures to explain why they selected the...
  2. supergee

    Is there a preferred true position standard?

    Thanks... I am ambiguous about the use of AI... As an educator I "should" be agaisnt it because we don't know the sources, the answers are sometime wrong, and.... I am trying to create NI (Natural Intelligence) in those students... I don't want to jump out of an airplane if I learn it was...
  3. supergee

    Is there a preferred true position standard?

    Thanks for the comment. I do teach them that there are generally 4 general risks when selecting position tolerance : 1- Will it run out of material? 2- If not, will it collide or be misalign? 3- If not, can the manufacturing process anticipated allow this position? (though we don't design FOR...
  4. supergee

    Is there a preferred true position standard?

    So one of my students gave a .005 inch true position tolerance on a hole used to attach a P-clip that will hold a loose electrical wire. I asked why and he said because the position is not important. I had to tell him that .005 is a rather tight tolerance concidering the use of positioning a...
  5. supergee

    composite tolerance at lmc : is it nonsense?

    The reason I asked to disregard that the hole are threaded is that this picture is from a student homework in my gd&t class. I asked the studends to create a series of geometries on a part that would require different gd&t concepts: LMC, composite tolerances, multi-segments tolerances, profile...
  6. supergee

    composite tolerance at lmc : is it nonsense?

    There is no composite in this drawing because I couldn't figure out a logical use for it, hence the question.
  7. supergee

    composite tolerance at lmc : is it nonsense?

    I was trying to think of a practical use of LMC when I realised that, though it is not forbiden in ASME y14.5 2018... it doesn't seem to make sense... at least with a patter of holes. The LMC enable one to have bonus tolerancing when material departs from LMC. one cannot increase that bonus...
  8. supergee

    Specifying ASME versions on drawings

    The year is mandatory. The example I give my students is dictionnaries. There is a dictionnary I had in high school back in the early 90's. Wi-Fi, Internet, youtuber were not in that dictionnay. The definition of cellular was there, but it didn't have anything to do with phones. Definition...
  9. supergee

    threaded hole depth feature of size?

    Theoretically, you are right. I winder, practically, how would one screw a threaded inserts while keeping true position? especially with a pattern...
  10. supergee

    threaded hole depth feature of size?

    Thank you all for the replies! @3DDave, I was preparing an example in what a good GD&T drawing should look for my students and, like @Bunrunduk said, I didn't want to overkill my dimensions but i don't like leaving things ambiguous: I first learned GD&T from experimenting with bad parts made...
  11. supergee

    threaded hole depth feature of size?

    Hi, IF I OVER SIMPLIFY There are two approches to dimensioning : one for feature of size and the other on for the rest. Feature of size are feature with two opposed surfaces. hole depth, in that sence are not feature of size. direct tolerancing on the dimension is used on FOS dimensions...
  12. supergee

    Unilateral tolerances-why?

    I am trying to reply to the essence of your question, which is WHY people model their parts at MMC. I can't say I completely agree with it, but here are the arguments. The reason I got from designers that use that approach is simple: to be able to locate interferences. When drawing at nominal...
  13. supergee

    Datuming drafted injection molded parts

    Suds, What I teach my student is You can't do real GD&T on a part without it's assembly, because it depends on the situation. in your case you show the mating part in red I beleive so good. Ideally, when practical, your datum should be in contact with another part. A surface that touches...
  14. supergee

    Total Runout - Long Shaft

    Cup909 Technically speaking, you should inspect the part per drawing. What I worder is if engineering selected either the datum correctly of the tolerances correctly. I came across long shaft (aerospace engine shaft) that needed precise runout. usually, the Datum should, when ever possible...
  15. supergee

    Recommanded tolerance for datum features

    Thank you all for your replies. Honestly, they're all quality answers. 3DDave, as usual, you demonstrate excellent comprehension of the standard. mfgenggear, jassco, and, well, everyone else, I don't remember reading replies from you before, but you make very valid points, and I thank you...
  16. supergee

    Recommanded tolerance for datum features

    Thanks for your input, mfgenggear. As a teacher, my job is to take existing experiences and summarize them so that students don't start from scratch. My predecessors used to teach GD&T symbols and their meanings. I try to teach them the effect of GD&T on practical cases: I don't want them to...
  17. supergee

    Datum ref frame B & C were both center plane, is that correct?

    I agree with Burunduk. Don't forget that Datum are mathematical models. The way I can explain it is with cad. imagine scaning a very crooket part and importing it in your favorite cad. lets assume that the order of precedence is A then B and then C. For datum A You would create a plane (P1)...
  18. supergee

    Recommanded tolerance for datum features

    Hello all, As some of you might know, I am teaching GD&T at the college level. I was wondering if there was a rule of thumb about the value to give for datum tolerances. I got a tip about that a few years ago from someone in the aerospace industry. The rule of thumb was to make the datum 10...
  19. supergee

    Measuring runout on a shaft relative to two datum surfaces... part 2

    Burunduk, 3DDave, Thank you for your answers! It confirms my original theory. I am trying to mix GD&T Design theory and Metrology in the same course in order for future designers to understand how the GD&T work and will be inspected and make the subject more "real". As I said, I understand...
  20. supergee

    Datum as plane tangent to two cylindrical surfaces

    Hi tw, Here is what the result might look like. I've inserted two example from ASME Gee

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