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  • #16
    Originally posted by alanganes View Post
    Just out of curiosity. Say I wanted to just help a guy in SA out and mail him a set of thread wires that pretty much fit in a regular envelope, how difficult or expensive would that likely be? A set would pretty much fit in a regular letter envelope.You could tape them to a sheet of folded up paper, for that matter.
    Any idea? Would it likely disappear in the mail?
    There's a few times I've wanted to do that -- PM him and ask? For sure the USPS could tell you or give a quote

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    • #17
      Originally posted by plunger View Post
      They are damn expensive.Even three wire guage sets are expensive. An here in Africa not so easy to get.Is there a way around it .........
      I have an extra Starrett (and also an extra Lufkin) 14-20 1" thread mic if it was any good to you and there was a good way to get it there and actually to you. The thread mics come 3 or 4 to a set, in thread ranges, and in 1" and 2" thread diameter ranges. The anvils are V-shaped, and each size fits only a range of threads. As it is I have too many of that size, and none of some others.

      You'd be better off with a set of thread wires, such as Pee-Dee. The set will come with a sheet explaining the calculation to get the measured thread pitch diameter. That's direct, and accurate, measures any thread of the usual US sizes, regardless of diameter (if you have a mic the right size for the diameter).

      The thread mic is only kinda accurate when just zeroed, it really should be set against a standard at or near the thread of interest, which is not necessarily easy to do unless you have a thread of the correct, known, size, or the like.

      Given the choice, the thread wires are the best (but not necessarily the most easy to use). The set will have several sets of three wires in it, along with the calculation data you need..



      1601

      Keep eye on ball.
      Hashim Khan

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      • #18
        I appreciate the gestures . I think our post office is useless. I have never done an oversees payment so need to look into how to do this. Im tech savvy challanged.

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        • #19
          If you just need to copy a thread you have or have a tap for, there is an easy way using a caliper. You can measure an OD thread (bolt, allthread, tap, etc.) with the caliper tips in the flanks of the thread on one side and the flanks of the thread on the other side, 1/2 pitch + or - from the 1st one. Then turn the threads on the lathe to get the same reading, measured the same way. If using a tap for the original measurement, make the part .002 to .003 smaller. By measuring on the flanks, you are matching pitch diameters, and omitting variations of the shape or size of the crest or root.
          Last edited by Toolguy; 09-15-2020, 11:08 AM.
          Kansas City area

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          • #20
            Originally posted by plunger View Post
            They are damn expensive.Even three wire guage sets are expensive. An here in Africa not so easy to get.Is there a way around it . ?What would happen if you made some sort of split piece anvil .One for each size thread Sort of like a split bush that has an internal thread but it is used as a comparator to a known thread . Would it work.
            If I'm understanding your proposal, you'd have a piece of rectangular stock, drill and tap it, then split it across the center. Then placing the two halves over a piece you're threading and measuring over the flats you'd see if the pitch diameter was correct or over or under size. One possible problem besides the calibration already mentioned, is that if the the threads you're cutting are more than a few thousandths oversize, the threaded anvils wouldn't fit over but would hang up at the front edges. That might be circumvented by machining more away so it comes closer to a set of two flat plates with thread grooves in them.
            .
            "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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            • #21
              There is a free program on my page, 3WIRE, which will calculate the measurement over wires for 60 degree thread forms. It calculates the ideal thread size first, but allows you to enter the wire size you used, after which it shows the required measurement over wires.

              An example output from the program is shown below.

              ============================================

              THREE WIRE THREAD MEASUREMENTS (60 degree threads)

              (M)etric or [I]mperial threads? I
              Thread pitch [20 tpi] ? 20

              Most common threads are single start.
              Number of starts [1] ? 1

              Best wire diameter to use = 0.7332 mm = 0.0289 in
              Wire diameter used [0.0289 in] ? 0.0289

              For American National Thread form, subtract 0.0325 in from
              major diameter (assumes p/8 flat on crest) to obtain pitch diameter.

              Major diameter of thread [0.25 in] ? 0.25

              pd = pitch diameter, mow = measurement over wires
              Calculate pd from mow (p) or mow from pd [m]? m

              Pitch diameter of thread [0.2175 in] ? 0.2175

              Measurement over wires = 6.6279 mm = 0.2609 in

              Regards, Marv

              Home Shop Freeware - Tools for People Who Build Things
              http://www.myvirtualnetwork.com/mklotz

              Location: LA, CA, USA

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              • #22
                Originally posted by TGTool View Post

                If I'm understanding your proposal, you'd have a piece of rectangular stock, drill and tap it, then split it across the center. Then placing the two halves over a piece you're threading and measuring over the flats you'd see if the pitch diameter was correct or over or under size. One possible problem besides the calibration already mentioned, is that if the the threads you're cutting are more than a few thousandths oversize, the threaded anvils wouldn't fit over but would hang up at the front edges. That might be circumvented by machining more away so it comes closer to a set of two flat plates with thread grooves in them.
                Yes ,something like that. It could even be cylindrical.It would be just used as a comparator on a thread you know is right. I realize that if your piece of hss is not ground right you could have issues but I use a carbide insert so it should be right. But I can see problems as to where the threads would sit in relation to each other for this to work well.Ive tried some stainless tig rods and it seems to work but even if they are slightly bent it would throw it out.

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                • #23
                  dont forget a thread is defined by the pitch diameter.

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                  • #24
                    Originally posted by dian View Post
                    dont forget a thread is defined by the pitch diameter.
                    This is very true. BUT.... given a known angle (60 degrees for ISO and UN threads) you can calculate that if a .1000 inch rod will touch the flanks of the thread at the pitch diameter a .1010 will touch a little higher on the flank at slightly larger diameter. The formula for using the "best thread wire size" has allowances for when you use the "nearly best".

                    For plunger's idea, you can use a split nut as a comparator, but by definition it would only work for one pitch. Effort should be taken to ensure that the roots of the male and female parts don't bottom out on the crests of the matching parts. If you use the "cut it till it looks like a thread, then use a file" method the split nut would not work reliably since the root of the nut is rounded and the crest of the bolt is (until filed) sharp.

                    Dan
                    At the end of the project, there is a profound difference between spare parts and extra parts.

                    Location: SF East Bay.

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                    • #25
                      Plunger I'd gladly to buy and send you either the Fisher wires or imported one if you could paypal me. You do need a wire that fits the flank, thats key vs measuring the bottom or crest. Its a lot better than a go no-go because it quantifies how much more has to come off....and how are you going to make a gauge without being able to measure the thread?

                      at the same time, don't over think it. Even very precise threads have a tolerance of a few thou. For a regular thread, any three round bits the same size that contact the flank will work. I remember reading about thread wires being done to millionths, BS. Do the math on how much a variance in dia will effect the measured pitch dia...it is amplified but still a small amount, not magnitudes. I'd say if you had three cylinders within .01mm you'd be more than good enough for all but the most demanding fine toleranced threads.

                      needles, drill rod, welding wire, knitting needles, dowel pins, wire, etc can work
                      Last edited by Mcgyver; 09-16-2020, 01:34 PM.
                      in Toronto Ontario - where are you?

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                      • #26
                        Originally posted by Toolguy View Post
                        If you just need to copy a thread you have or have a tap for, there is an easy way using a caliper. You can measure an OD thread (bolt, allthread, tap, etc.) with the caliper tips in the flanks of the thread on one side and the flanks of the thread on the other side, 1/2 pitch + or - from the 1st one. Then turn the threads on the lathe to get the same reading, measured the same way. If using a tap for the original measurement, make the part .002 to .003 smaller. By measuring on the flanks, you are matching pitch diameters, and omitting variations of the shape or size of the crest or root.
                        You could get a comparator thread mic like a Starrett 210. Much cheaper than their anvil type thread mics. Then as toolguy says you can turn the threads on your lathe using the mic to get the same dimension as what you are trying to copy.

                        You could also use music wire if you can find it. It comes in sizes like every .002. A much wider choice of diameters than MIG wire.

                        JL...............
                        Last edited by JoeLee; 09-15-2020, 08:44 PM.

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                        • #27
                          I do think that given your situation, using improvised wires along with either the straight up math or Marv Klotz 3WIRE program (there are similar calculators out on the web*) seems the most direct and least expensive way to do this. You could maybe buy 3 sets of the cheapest small drill bits you can find just to keep for use as thread wires. They don't need to be particularly accurate to any given size as you can mike them and plug the numbers in. You really just need 3 that are reasonable close to the same size. As noted in other replies, pretty much anything close will do. You can pretty much make your own set of thread wires for whatever work you have at hand.

                          I had always just machined threads to fit the mating part, until I had a situation where the mating part was just too big and heavy to use for trail fitting on the lathe. It was also across town and attached to a big piece of equipment. So I got a set of pretty cheap thread wires and used those. Parts fit as designed and they really were not as hard to use as some seem to make them out to be. It does feel like you need 3.5 hands at times, but it really was not very difficult.



                          *just one that comes up in a quick search: https://www.cgtk.co.uk/metalwork/cal...rewmeasurement

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                          • #28
                            Originally posted by Mcgyver View Post

                            at the same time, don't over think it. Even very precise threads have a tolerance of a few thou. For a regular thread, any three round bits the same size that contact the flank will work. I remember reading about thread wires being done to millions, BS. Do the math on how much a variance in dia will effect the measured pitch dia...it is amplified but still a small amount, not magnitudes. I'd say if you had three cylinders within .01mm you'd be more than good enough for all but the most demanding fine toleranced threads.
                            High accuracy thread wires are only really needed for verifying thread gauges. 1/4" 3A thread has about 0.05mm min-max tolerance. Gauge made for checking 3A thread might have 0.005mm tolerance itself and thread wires used to verify the gauge are hopefully 1 um or better.


                            Location: Helsinki, Finland, Europe

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                            • #29
                              Originally posted by alanganes View Post
                              I do think that given your situation, using improvised wires along with either the straight up math or Marv Klotz 3WIRE program (there are similar calculators out on the web*) seems the most direct and least expensive way to do this. You could maybe buy 3 sets of the cheapest small drill bits you can find just to keep for use as thread wires. They don't need to be particularly accurate to any given size as you can mike them and plug the numbers in. You really just need 3 that are reasonable close to the same size. As noted in other replies, pretty much anything close will do. You can pretty much make your own set of thread wires for whatever work you have at hand.
                              Note that the 3WIRE program computes the optimum wire size but provides an input whereby you can enter the diameter of the wire you actually used; it need not be the optimum.

                              Regards, Marv

                              Home Shop Freeware - Tools for People Who Build Things
                              http://www.myvirtualnetwork.com/mklotz

                              Location: LA, CA, USA

                              Comment


                              • #30
                                Originally posted by Mcgyver View Post
                                Plunger I'd gladly to buy and send you either the Fisher wires or imported one if you could paypal me. You do need a wire that fits the flank, thats key vs measuring the bottom or crest. Its a lot better than a go no-go because it quantifies how much more has to come off....and how are you going to make a gauge without being able to measure the thread?

                                at the same time, don't over think it. Even very precise threads have a tolerance of a few thou. For a regular thread, any three round bits the same size that contact the flank will work. I remember reading about thread wires being done to millions, BS. Do the math on how much a variance in dia will effect the measured pitch dia...it is amplified but still a small amount, not magnitudes. I'd say if you had three cylinders within .01mm you'd be more than good enough for all but the most demanding fine toleranced threads.

                                needles, drill rod, welding wire, knitting needles, dowel pins, wire, ec can work
                                Thanks for the offer Mcgyver.I guess I might be overthinking it and if I can find some suitable wire,just try that .I am math challenged so will use them as a comparator against a known thread.

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