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  • Metric Thread help needed.

    Trying to repair my rolling walker which has a thread stripped out in the leg. The thread on wheel is steel and is good so I need to make a new bushing.

    The male threads measure 0.459 major dia. and 0.397 minor dia. My metric thread gauge will screw onto the 12mm thread shaft in both the 1.5 and 1.75 holes. Looking at the tool catalogs it would appear that the 1.75 is the more common size. I would like to confirm that before ordering a tap.

    My Nardini lathe has a 15 tpi capability which computes to a lead that comes out between the 1.5 and 1.75 metric lead. The plan is to make a new bushing using the 15 tpi setting. Any thoughts?
    Byron Boucher
    Burnet, TX

  • #2
    Originally posted by Boucher
    Trying to repair my rolling walker which has a thread stripped out in the leg. The thread on wheel is steel and is good so I need to make a new bushing.

    The male threads measure 0.459 major dia. and 0.397 minor dia. My metric thread gauge will screw onto the 12mm thread shaft in both the 1.5 and 1.75 holes. Looking at the tool catalogs it would appear that the 1.75 is the more common size. I would like to confirm that before ordering a tap.

    My Nardini lathe has a 15 tpi capability which computes to a lead that comes out between the 1.5 and 1.75 metric lead. The plan is to make a new bushing using the 15 tpi setting. Any thoughts?
    1.75mm pitch is the standard ISO M12 Coarse pitch, so a good bet.

    1.75mm pitch is 14.51tpi so probably close enough or get a tap.

    Steve Larner

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    • #3
      Metric threads are almost always the standard sizes. Unfortunately many suppliers make it look confusing by simply lumping all metric threads in one big list. As Steve says, your fastener is almost certainly a standard M12 which is 1.75 pitch. Whether 15 tpi is close enough will depend on how long the thread is. However is it necessary to replace this with a metric bush? Can you replace both with another fastener that you do have the appropriate tap for?

      Comment


      • #4
        tanto you are right on. The beauty of metric threads is that 99% are standard, meaning they are the coarsest thread for a given metric size. You never list the pitch unless for some reason you must use a fine thread. The stupidity of some people listing the pitch regardless, forces one to look up a table to see if there is not another coarser thread available.
        Using only standard (coarse) threads allows a shop to greatly reduce the inventory on screws and nuts. ANSI screwed this up real good.

        Comment


        • #5
          What's stupid about giving full details about a thread. Assuming that it is a standard pitch because the pitch is not identified can lead to dissapointment.

          Phil

          Originally posted by Juergenwt
          The stupidity of some people listing the pitch regardless, forces one to look up a table to see if there is not another coarser thread available.

          Comment


          • #6
            I'm having a similar problem in that a piece of threaded rod I have measures 6.35 Dia. but am unsure whether the thread is 0.0385" or 0.05" pitch ?

            Regards Ian.
            You might not like what I say,but that doesn't mean I'm wrong.

            Comment


            • #7
              I don't understand, are you saying you can't tell if it is 20 or 26 threads per inch. Measure an inch and count them!!!

              Phil

              Edit: Do you not have a thread gauge.

              Originally posted by Circlip
              I'm having a similar problem in that a piece of threaded rod I have measures 6.35 Dia. but am unsure whether the thread is 0.0385" or 0.05" pitch ?

              Regards Ian.

              Comment


              • #8
                Originally posted by philbur
                What's stupid about giving full details about a thread. Assuming that it is a standard pitch because the pitch is not identified can lead to dissapointment.

                Phil
                It is stupid as it is standard practice to just tell it is M12. If with metric you tell M12 X 1.75, it means that it ain't a thread from the "most used"/"recommended" list but a fine/special thread.

                If it is M12, then it is M12 and not "M12 x 1.75".
                Amount of experience is in direct proportion to the value of broken equipment.

                Comment


                • #9
                  A little more explanation

                  I don’t have a lot of metric resources. A metric nut with a longer engagement would be a better standard than this thin thread gauge. Some of the original confusion results from two of the gauge holes seeming to work as illustrated below.


                  This shows the thread gauge in the 12X1.5 hole


                  This shows the thread gauge in the 12x1.75 hole


                  This view of the wheel illustrates why a simple change the bolt thread is not a good option.


                  In this application there will need to be more than two diameters of thread engagement, which is why, identifying the correct thread becomes increasingly important. The bushing is shown at the lower right.

                  As stated earlier I have no way of getting a tap over the week end so I will try single pointing a 15 tpi which has a lead between the 1.5 and 1.75
                  Byron Boucher
                  Burnet, TX

                  Comment


                  • #10
                    Strange that 1.75 is considered 'standard'? In automotive imports (honda, toyota, nissan, etc.) the standard metric bolts are almost always on the fine side of the chart. In this situation the 12m would be a 1.25 pitch, that is what I see in cars as being the standard. In fact I don't remember the last time I saw a "coarse" threaded metric bolt.
                    Andy

                    Comment


                    • #11
                      Check it with a metric nut of known pitch, the extra length will let you determine if it's a 1.5 or 1.75 pitch as it will only thread full length at the correct pitch, conversly, a bolt will do the same for the nut that goes into.
                      I don't know about you, but I'm sure I can find a metric nut or bolt that size residing on/in something in my shop or car. (even if it's "american" made)
                      I cut it twice, and it's still too short!
                      Scott

                      Comment


                      • #12
                        Providing the provider/user is aware of what is standard practice. It they are not then they could get into a whole bunch of trouble. Not everybody is as knowledgeable as yourself. It's interesting to note that all metric thread tables include the pitch size against the standard thread. Why do they do that, do they not realise everybody knows that it is the standard pitch and therefore stating the pitch is stupid.

                        To include additional information is never stupid. Unnecessary maybe, stupid never. To leave out information that may confuse the uninformed is. Every Yank/Limy/Digger who is not familiar with standard practice regarding metric thread definitions is going to ask -OK it's M12 but what's the pitch? Not many of them bother to read the ISO standard before they go to the hardware store.

                        Phil

                        Originally posted by Jaakko Fagerlund
                        It is stupid as it is standard practice to just tell it is M12. If with metric you tell M12 X 1.75, it means that it ain't a thread from the "most used"/"recommended" list but a fine/special thread.

                        If it is M12, then it is M12 and not "M12 x 1.75".

                        Comment


                        • #13
                          Originally posted by philbur
                          Providing the provider/user is aware of what is standard practice.
                          To include additional information is never stupid. Unnecessary maybe, stupid never.
                          Phil
                          That is one of the nice things about "STANDARDS", there are so many of them.

                          To include additional information is never stupid. Unnecessary maybe, stupid never.

                          A big ABSOLUTELY!!!!
                          ...lew...

                          Comment


                          • #14
                            Originally posted by vpt
                            Strange that 1.75 is considered 'standard'? In automotive imports (honda, toyota, nissan, etc.) the standard metric bolts are almost always on the fine side of the chart. In this situation the 12m would be a 1.25 pitch, that is what I see in cars as being the standard. In fact I don't remember the last time I saw a "coarse" threaded metric bolt.
                            Well the coarse series is standard and the Fine pitch should have the pitch specified, that's how it was when I was a cad designer and Engineering manager. In general engineering the only Metric fine I have come across are on pneumatic fittings.

                            As noted fine pitch quite common on cars but so was BSF when BSW was the std coarse.

                            Steve Larner

                            Comment


                            • #15
                              philbur - read my post again. Nowhere in the rest of the world do people have a problem with M2, M3, M4, M5, M6, M8, M10, M12 etc..Fine threads are usually not kept in stock thereby reducing the inventory. If a company decides to use a fine thread in it's product it will do so for a reason. So if fine threads are used on a bike than the company designed it that way for a reason. You can be sure that the same company will use nothing but standard sizes in it's everyday operations. In day to day usage the standard metric size (coarse) is all that is needed.
                              It is only in the US where we seem to have a problem because we are so used to listing the pitch for inch threads.
                              I like the reply from Jaakko Fagerlund.
                              Last edited by Juergenwt; 08-27-2011, 03:07 PM.

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