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  • Print Reading Help

    I am building a stirling engine from a kit and need a little help in deciphering some of the symbols on the print. This page is a cross section of the flywheel.



    What does the triangle thing with the 1.6 represent?

    Are the boxes with the "A" and the 0.05 and 0.10 tolerances? Why does one box have slashes and the other the upside down T symbol.

    As you can tell I'm somewhat new to the hobby and any help would be appreciated.

    Also what kind of thread is a M3-7H. I get the 3mm part but what does 7H mean?

  • #2
    Try to answer in order
    1. surface finish its in metric so i`m not familarwith the1.6.

    2. // parallel to datum up side down T square to 90؛ perpendicular to datum

    3. class of thread 7H
    Hope this helps
    Last edited by lane; 03-22-2007, 09:27 PM.
    Every Mans Work Is A Portrait of Him Self
    http://sites.google.com/site/machinistsite/TWO-BUDDIES
    http://s178.photobucket.com/user/lan...?sort=3&page=1

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    • #3





      .
      .

      Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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      • #4
        Thank you for your reply. If I could get some clarification on the tolerances. I'm assuming the upside down T at .05 means that the hole has to be square to the datum by the .05...ie the hole is not crooked. It's not referring to the diameter of the hole itself, correct?

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        • #5
          Thank you John, I searched google for and hour looking for a list of symbols like that.

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          • #6
            Originally posted by Wess
            Thank you for your reply. If I could get some clarification on the tolerances. I'm assuming the upside down T at .05 means that the hole has to be square to the datum by the .05...ie the hole is not crooked. It's not referring to the diameter of the hole itself, correct?
            The hole should be prependicular to the bore within .05mm as I see it.

            IMHO from experience,people who draw things and insist on using symbols and DON'T provide a symbol legend with the drawing should be shot.
            I just need one more tool,just one!

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            • #7
              Heck, it's "just" a flywheel. You want the hole for the shaft to be in the middle and everything pretty much around it and not too much off center or balance. If you want it pretty polish it up but for the most part small engine flywheels are small engine flywheels and all follow pretty basic principles.

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              • #8
                [QUOTE=
                IMHO from experience,people who draw things and insist on using symbols and DON'T provide a symbol legend with the drawing should be shot.[/QUOTE]

                Aint it the truth!!!
                If everything seems to be going well, you have obviously overlooked something........

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                • #9
                  Passed a class on this once

                  I once passed my class that included Geometric Dimensioning and Tolerancing but have now forgotten almost 100% of it. Fortunately, I do have the reference book and am now taking the chance to relearn.

                  From my perusal of Geo-Metrics III describing the ANSI Y14.5-1994 Geometric Dimensioning and Tolerancing rules,I cannot find the triangle symbol like that. This print appears to use symbols that are not in the 1994 version of the ANSI/ISO standard.

                  Enough of this is standard I can explain some of this based on what I know:

                  The rectangles divided into three parts is called a feature control frame. It is basically an imperative sentence of the form "What", "How Much", "Measured with Respect to".

                  The FCF in the upper right of the print reads that the top of the flywheel is parallel to datum A (the bottom of the flywheel) such that two imaginary planes constructed .05 above and .05 below the top of the flywheel will not intersect the top of the flywheel.

                  The Octagon with an A in it describes the plane of the bottom of the flywheel as "datum A" as near as I can tell.

                  The FCF at the bottom left hand side of the print says that the hole drilled in the center of the flywheel will be perpendicular to datum A (the bottom of the flywheel) such that two imaginary planes drawn vertically on the print .025 to the left and .025 to the right of the correct hole location will not intersect the line drawn between the center of the hole on the top of the flywheel and the cneter of the hole on Datum A (The bottom of the flywheel).

                  The only other thing I can do since I can't locate a reference about triangle symbols is ask if they reference notes at the bottom of the drawing or on another sheet.

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                  • #10
                    Non Standard Symbols. Shame on them

                    Having seen the other replies that came in as I wrote mine, I have to say that legends are unnecessary. I have a 350 page book on my desk that describes what each symbol means, how it is supposed to be used and how you can measure that the part meets the spec. The symbols are very precisely defined and sometimes the precise definition is rather complicated.

                    For the computer programmers among us, it's just like a visual version of perl

                    Now, for those who use non-standard symbols and worse don't define them, your torture in hell should be confined to reading the prints of one of your buddies who uses non-standard symbols different from yours.

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                    • #11
                      Just make every thing dead nuts and you dont have to worry about those symbols
                      Every Mans Work Is A Portrait of Him Self
                      http://sites.google.com/site/machinistsite/TWO-BUDDIES
                      http://s178.photobucket.com/user/lan...?sort=3&page=1

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                      • #12
                        But what if your dead nuts are being done with half dead nuts

                        Or, how about dead half-nuts?

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                        • #13
                          Thanks for all the replies. Between all of them I now understand all the symbols. It's actually kind of obvious now that I know what they mean. I realize it's only a little flywheel , but I wanted to learn what they all meant.

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                          • #14
                            machinery's handbook also has a few pages on the subject.
                            tin
                            I know this only helps if you have a fairly recent copy
                            Ad maiorem dei gloriam - Ad vitam paramus

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                            • #15
                              Originally posted by ckelloug
                              Having seen the other replies that came in as I wrote mine, I have to say that legends are unnecessary. I have a 350 page book on my desk that describes what each symbol means, how it is supposed to be used and how you can measure that the part meets the spec. The symbols are very precisely defined and sometimes the precise definition is rather complicated.

                              Now, for those who use non-standard symbols and worse don't define them, your torture in hell should be confined to reading the prints of one of your buddies who uses non-standard symbols different from yours.
                              You must work for NasaThey without a doubt are the single greatest offender of non-standard symbols use.

                              The afore mentioned symbol is a surface finish symbol in ISO,but it notes a micro-inch finish spec of 1.6 .That would equate to .0016"/rev lathe finish,or in laymans terms "machined so you can your ugly teeth in it"

                              For insight in the surface finish symbol mess look here,it's truly pathetic-

                              http://www.qualitydigest.com/june01/html/surface.html

                              Furthermore CAD programs have only increased the number of glaring and not so glaring mistakes being made in drawings.I typically find mistakes in 60% or better of the CAD drawings I recieve at work.It costs me time and money and I have begun charging for editing.

                              I was working with a EE the otherday who said it was a shame CAD programs didn't have a symbol for smoke when someone draws a dead short
                              I just need one more tool,just one!

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