Bonus for External Thread........

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Bonus for External Thread........

    so far, i read lot of threads in this forum on calculating bonus for Threaded Profiles either it can be internal or external, and many suggestions were to consider that as RFS.
    Butt today i got a Drawing with a true Position callout for M5 External Thread ( 0.00 LMC | A LMC |).
    i need some suggestions to settle this........

    Thanks in Advance....................

  • #2
    TP of 0 is impossible. Had that same problem. Every hole was bad because of the ridiculous call-out.
    Darroll
    2018R2

    Comment


    • #3
      This callout is legit & totally possible. You just need LMC or MMC called out to give you bonus tolerance.

      If the OD thread is supposed to be Ø1.000±0.005 and measures 1.004, then you'd have 0.009 of bonus tolerance (because you're OD is 0.009 higher than low limit). This 0.009 becomes your new overall T.P. allowance for that feature. With this example, due to the diameter size I used, if we were doing a standard diametric T.P., your position could deviate as much as 0.00318" in both axes and you'd still comply with the 0.000 T.P.


      *Please note I just gave you the "usual" explanation of T.P. and how most engineers/inspectors interpret it when doing plate layout. If your print says Y14.5M you should be using XACT measure so it calculates datum shift and all of that jazz properly...if not my method worked fine for the past 50 years for the guys who taught me and can be done with the legacy dimensioning

      **When you measure the thread make sure you use the "pitch" option!
      Last edited by DAN_M; 07-25-2019, 07:14 AM.
      Beep beep beep..

      Comment


      • #4
        We use bonus a lot on most of our threads ID and OD. Most of our thread are standard threads so i look up the TOL for Major or Minor threads. Instead of chasing the threads with a spiral scan. I use a cylinder line scan make sure the lines are opposing each other and i use max inscribed or circumscribed depending on ID/OD. Had decent results with this method.

        Comment


        • thomas pilc
          thomas pilc commented
          Editing a comment
          i agree in the aerospace industry we get .000 TP MMC all the time and i have just come to measure all threads with cylinder line scans with max inscribed or min circumscribed filters to get your bonus and location all in one. and if you are gonna use the LMB on your datum u have to use xact mesure but in my opinion if you can check it with out datum shift and it passes do that the use of datum shif makes the report much harder for operators to move features the way they need to

      • #5
        Originally posted by DAN_M View Post
        This callout is legit & totally possible. You just need LMC or MMC called out to give you bonus tolerance.

        If the OD thread is supposed to be Ø1.000±0.005 and measures 1.004, then you'd have 0.009 of bonus tolerance (because you're OD is 0.009 higher than low limit). This 0.009 becomes your new overall T.P. allowance for that feature. With this example, due to the diameter size I used, if we were doing a standard diametric T.P., your position could deviate as much as 0.00318" in both axes and you'd still comply with the 0.000 T.P.


        *Please note I just gave you the "usual" explanation of T.P. and how most engineers/inspectors interpret it when doing plate layout. If your print says Y14.5M you should be using XACT measure so it calculates datum shift and all of that jazz properly...if not my method worked fine for the past 50 years for the guys who taught me and can be done with the legacy dimensioning

        **When you measure the thread make sure you use the "pitch" option!
        1.000+/-0.005 (M) and measure 1.004 gives 0.001 of bonus tolerance, 1.000+/-0.005 (L) and measures 1.004 gives you 0.009 bonus tolerance (all for an O.D., for I.D it is flipped)
        sigpic
        Originally posted by AndersI
        I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

        Comment


        • #6
          the bonus tolerance comes from the pitch diameter not the OD

          Comment


          • DAN_M
            DAN_M commented
            Editing a comment
            The bonus comes from the feature being called out by the DRF. Could be the major, minor, PD...whatever the print calls out.

          • Schlag
            Schlag commented
            Editing a comment
            Dan M is correct. If its not called out it is the pitch by default. Stupid thing is, in what scenario on a threaded "fit" of 2 parts is the MAJOR ( or minor ) Ø the mating surface ?

          • Mikeg
            Mikeg commented
            Editing a comment
            Most of our prints callout to the minor

        • #7
          Finally got response from customer , as DAN_M said, they ask me to consider the major Dia for Lmc.........

          Capture.PNG

          thanks for all..........

          Comment


          • #8
            How are you going to measure that on the CMM ? Or are you going to use it as a keyed in variable ?

            Comment


            • Schlag
              Schlag commented
              Editing a comment
              Yep, I got that part ..Just tying to look down someone elses rabbit hole when it comes to bonus on threads..... Is that wrong ?

            • Thiyagu_Raj
              Thiyagu_Raj commented
              Editing a comment
              How are you going to measure that on the CMM ? Or are you going to use it as a keyed in variable ?

              Using auto-circle feature with pitch
              Last edited by Thiyagu_Raj; 07-29-2019, 10:40 AM.

            • Schlag
              Schlag commented
              Editing a comment
              That doesn't actually measure the pitch Ø it just follows it. How do you apply the LMC ? And to what size ?

          • #9
            That doesn't actually measure the pitch Ø it just follows it. How do you apply the LMC ? And to what size ?
            ​​​​​​Or else need to measure the major Dia with micrometer and keyin the value....

            Comment


            • #10
              I've suggested this method a few times now on here:
              -Measure a line of points along the edge of the threads, parallel with threaded cyl axis, at least 1.5 pitches long.
              -Equally space the points rather densely (like ten points per pitch or more)
              -Extract the max point using an assign
              -Origin your Z to the max point (high point/MAJOR DIA of thread)
              -THEN measure a circle/cylinder with the pitch angle defined, from zero origin point you just aligned.
              --Probe will make contact with the max dia of your threads all the way down the part.

              If you want to take it to another level:
              -Sample more hits to extract two or three high points, with higher precision (a slow scan would work well here if capable).
              -Calculate actual pitch of the threads (extract the 2 or 3 pitches/highest points, average the z distance between them).
              -Define actual pitch as your cir/cyl pitch value!
              --Origin and measure from zero point of first pitch high point, with your assigned actual measured pitch.
              --Probe will make contact with the max dia of your threads all the way down the part along the actual measured pitch of the threads.
              Last edited by louisd; 07-29-2019, 12:20 PM.

              Comment


              • Schlag
                Schlag commented
                Editing a comment
                Nice. I went back to the beginning of the post and note it was EXTRNAL thread.

            • #11
              louisd could you post some code for sample

              Comment


              • louisd
                louisd commented
                Editing a comment
                honestly, I don't have the time to make it this week. follow the pseudocode.

            • #12
              Finally, I learned something today... Thanks all for your valuable inputs

              Comment

              Related Topics

              Collapse

              Working...
              X