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  1. #101
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    Quote Originally Posted by SeymourDumore View Post
    ....
    Nowadays you're expected to quote and work from a solid model instead of a B/P.
    Confused here as to tolerances.
    If you quote a solid model at .005 tolerances and then the end print comes though at 5-10 millionths?????
    Think a simple gauge pin. Basic cylinder but how does the model tell me the needed info.
    Is the tolerance and finish in the model file without a print. If not +/-.005 gauge pins are so much cheaper to make
    Bob

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    Quote Originally Posted by CarbideBob View Post
    Confused here as to tolerances.
    If you quote a solid model at .005 tolerances and then the end print comes though at 5-10 millionths?????
    Think a simple gauge pin. Basic cylinder but how does the model tell me the needed info.
    Is the tolerance and finish in the model file without a print. If not +/-.005 gauge pins are so much cheaper to make
    Bob
    Some CAD systems are capable of including tolerances within the model, provided you're reading the native model in the requisite software. It's generally a lot more work for the manufacturer and a greater chance of tolerances being overlooked, but CAD jockeys and MBA's love it because it saves them having to make a print.

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    Quote Originally Posted by JCByrd24 View Post
    I just realized work has a copy of ASME Y14.5 2009 Dimensioning and Tolerancing, some further definition from that document:

    1.3.56 Size, nominal: the designation used for purposes of general identification.

    1.6 TYPES OF DIMENSIONING
    Decimal dimensioning shall be used on drawings except where certain commercial commodities are identified by standardized nominal size designations, such
    as pipe and lumber sizes.
    I can remember SAE heavy equipment builders moving those remaining fraction details to decimal inch on ALL prints… The good news was that at that time you could get really good chrome clad 10’ tape measures for 10 bucks (these were GOOD tapes with razor sharp markings). I haven’t seen one of those for a very long time…

    BTW the new details did say 4.25” for 4¼ but it was easy to estimate between the .1” lines.

    Good luck,
    Matt

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    Quote Originally Posted by mhajicek View Post
    Some CAD systems are capable of including tolerances within the model, provided you're reading the native model in the requisite software. It's generally a lot more work for the manufacturer and a greater chance of tolerances being overlooked, but CAD jockeys and MBA's love it because it saves them having to make a print.
    Not only that, but there are some places IME that are actively trying to go paperless for the environment and whatnot...

    Judging (and I don't know you obviously) from some of your responses, I am guessing you are not an "engineer friendly" guy, IE you don't seem to like them. I've worked with bad and good ones, and when they are good, it's great! When they are bad...

    I had one guy (and I had just moved out of state for this job) tell me "the last guy never had a problem with this". It was like an SAE port detail, but nothing standard and I was questioning if we had a tool for it or if I needed to have one made. Well I ended up finding the old program and saw he had 3d surfaced the oddball angles - problem solved. BUT that asshole had to be a jerk about it and offer nothing (I assume he had no clue how it was made, not necessarily his fault) in the way of help and laid everything at my feet. Jerk-off!

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  7. #105
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    Quote Originally Posted by Mike1974 View Post
    Judging (and I don't know you obviously) from some of your responses, I am guessing you are not an "engineer friendly" guy, IE you don't seem to like them.
    I like them fine, it just takes a while to get each new engineer trained in!

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  9. #106
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    Quote Originally Posted by JCByrd24 View Post
    Real versus nominal value - Wikipedia

    Here's the link for the third time. The word size appears 25 times on the page and you're saying it doesn't refer to size....I don't think it's me who's stuck in my own world.
    I'll just give up there. If you believe "Nominal Value" refers only and exclusively to size, then there ain't more to talk about.

    Quote Originally Posted by JCByrd24 View Post
    So for your second example of .3145-.3130 (should be .3130-.3145)
    Again, Why should it be that way?

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    I’m getting trolled right?? I never said it’s exclusive to size. I used voltage as an example. You insisted that size was not mentioned in the article. It was, a lot.

    ASME Y14.5 and common sense say the small limit should be before the large when shown on one line. You don’t say I’ll arrive to work between 7 and 6:45 do you?

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    Quote Originally Posted by JCByrd24 View Post
    I’m getting trolled right?? I never said it’s exclusive to size.
    Really?
    Post#71

    Quote Originally Posted by JCByrd24 View Post
    I don’t see what point you’re trying to make. It doesn’t say the word nominal may be standard or proprietary, it specifically says sizes. You seem to think the word can mean anything


    Quote Originally Posted by JCByrd24 View Post

    ASME Y14.5 and common sense say the small limit should be before the large when shown on one line.
    If ASME says anything about what should be before what, I don't know.
    But!
    In 23 years of looking at aerospace prints, I don't recall ever seeing a single limit definition where lower was before upper.
    That is for PW, Boeing, Lockheed, Sikorsky, Hamilton, and a few others.
    At the same time, commercial prints come in any variety of limit definitions, which is why I thought there was no such criteria.

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    That quote was in response to you saying basically “nominal is what I say it is” because the article said “it” can be standard or proprietary so I can make it whatever. I was pointing out that in that case the “it” was a size, not a the word nominal. I was in no way saying nominal is always referring to size.

    I find it very hard to believe you’ve never seen a properly dimensioned drawing in 23 years, but you surprise me with every post. Edit: maybe all the drawings you’ve seen are proper in the upper limit being above the lower vice on the same line.

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    Quote Originally Posted by JCByrd24 View Post
    That quote was ...
    I'm done with this.
    Please, have a nice day!

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    Quote Originally Posted by Matt_Maguire View Post
    A “basic circle” (B.C.) on a detail is a description, it has no size, no tolerance. It’s a PERFECT circle, I’ve never made one and will never know anyone that has. All the other crap called out on the detail regarding the basic circle we have done. Patterns on a specified angle of rotation, concentricity, sizes, ovality, all of it imaginary.
    Did you have to bring pitch diameters into this ?

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    Quote Originally Posted by mhajicek View Post
    I like them fine, it just takes a while to get each new engineer trained in!
    Wut? You train them?
    And there's me thinking you *beat them into shape*...

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    I don't think I have previously had any major disagreements with Seymour, but he seems pretty damn adamant on this "the model should be perfect" and now "nominal means blah blah blah..??"

    I didn't quote bob on this, but he makes a good point on quoting to a model. It would be rare, IMO, to have the exact same software to import said model and pull tolerances off of it. Again, why I say the model doesn't matter too much. Sure, complex 3d surfacing, you need the model correct and to the mean - basic shapes with floors, walls, bores, not so much, but that is just one man's opinion...

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    Quote Originally Posted by Mike1974 View Post
    Sure, complex 3d surfacing, you need the model correct and to the mean - basic shapes with floors, walls, bores, not so much, but that is just one man's opinion...
    My issue here...is that unless you check the model to all the print dims (and it could be a lot of dims to check...) when you 'gram a model you pick geometry and away you go.
    The issue is then when a floor is modelled on bottom so your first part comes off the machine 5 microns in tolerance...just....in....limit....
    You could pull the tool up with length/wear comp but that isn't right for the next time the prog runs...

    So you then realize and go DOH! and go back to the CAM to lift up the surface or plus up the cutter on your stock to leave and then re-post etc and then have to re-verify etc etc etc.
    Same as sidewalls...if you'd programmed with comp active you could edit the radial offset value etc.
    So to me it matters big time.

    What isn't so important though () are small hole sizes that will be drilled/reamed. If they're say 5.05/5.00 and modelled on 5.00 then i'll live with that.
    But surfaces and walls and floors and bores - get it right and do your job!

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  20. #115
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    Quote Originally Posted by Mike1974 View Post
    but he seems pretty damn adamant on this "the model should be perfect"

    I didn't quote bob on this, but he makes a good point on quoting to a model. It would be rare, IMO, to have the exact same software to import said model and pull tolerances off of it. Again, why I say the model doesn't matter too much. Sure, complex 3d surfacing, you need the model correct and to the mean - basic shapes with floors, walls, bores, not so much, but that is just one man's opinion...

    Mike

    If you read Barbter's response above, you'll see that if your solid model is not to median ( or perfect ), then the options for the machinists ( us ) is as follows:
    1: You do nothing to the solid, program off of it and hope for the best. Adjust offsets ( if possible ) to get next part w/in tolerance.

    2: You interrogate all critical features and either:
    a: edit the model to "perfect" or preferred dimension
    b: edit the toolpath in CAM to get the individual feature to target

    In either case, if the supplied model was already perfect, none of these would be necessary on the machining end, AND!!! it would harm you nothing
    on the designing end except a few minutes extra time.

    Like Chris said, Median form will never hurt, but extreme can.

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  22. #116
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    Discussions like this are good for the thought processes and in my opinion show us where, we as a group need to improve.

    I don't really care, everything is just a number. If you give me a print, I'll do my best.

    Now if you want me to read your mind to figure out exactly what your thought process is on the damn print. You can go away....

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    Quote Originally Posted by SeymourDumore View Post
    Mike

    If you read Barbter's response above, you'll see that if your solid model is not to median ( or perfect ), then the options for the machinists ( us ) is as follows:
    1: You do nothing to the solid, program off of it and hope for the best. Adjust offsets ( if possible ) to get next part w/in tolerance.

    2: You interrogate all critical features and either:
    a: edit the model to "perfect" or preferred dimension
    b: edit the toolpath in CAM to get the individual feature to target

    In either case, if the supplied model was already perfect, none of these would be necessary on the machining end, AND!!! it would harm you nothing
    on the designing end except a few minutes extra time.

    Like Chris said, Median form will never hurt, but extreme can.
    As simple as this!

    I don't understand why it needs to be discussed.

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    Quote Originally Posted by sinha View Post
    As simple as this!

    I don't understand why it needs to be discussed.
    Because you understand!

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    I am of new-ish school camp on models/prints. Prints are generated from model now days (if modeled). The model is datum, the print gives information about tolerances, general layout, material, and notes. If the model is not right, the print wont be right, and I see more fubared dimensions in prints now than 5 years ago because lazy cad jockeys pulling dimension lines from seeming random work points in space.
    That said, model to what you want in the end- easier for everyone.

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    Quote Originally Posted by SeymourDumore View Post
    a: edit the model to "perfect" or preferred dimension
    Well, if ya wanna get technical, you can't. Computers operate in binary while us yumans use decimal and frequently the twain don't meet exactly


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