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NC or NF Threads ??

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  • NC or NF Threads ??

    For the past few days I have been attempting to make the ball turning fixture that I ask Bruno the plans for. Well, after a lot of frustration and nasty words, I have come pretty close to translating the Metric (not the German} into something that I might be able to make work.. Every thing went pretty well until it came time to make the handle that rotates the fixture. Do I use NC or NF threads. My supply of taps and dies is pretty limited. Most are older than most of you guys. Not being but a Hobby Chip Maker, what is the preferred tread for this type of application? I think I need to make a few purchases of taps and dies, but want to get what is best for the job. What say you?
    _____________________________________________

    I would rather have tools that I never use, than not have a tool I need.
    Oregon Coast

  • #2

    Can you post a print ?

    -D
    DZER

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    • #3
      As I understand it, the finer NF thread will allow you to exert more pressure per turn. If this is for the handle, pick a pitch that will give you at least 4 threads per diameter. As an example, 20 TPI for a 1/4 inch rod gives you 5 threads for every 1/4 inch. There is probably a more scientific way to do it.

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

      Location: SF East Bay.

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      • #4
        Yes, seeing the print would help. What metric thread does it call for?

        And what does this thread do? I have seen many different types of ball turning devices. If this thread is just for attaching a handle, then either a coarse or fine English thread of a similar diameter would probably work. But if it has something to do with the function of the device, then it would really help to see the plans.
        Paul A.
        SE Texas

        Make it fit.
        You can't win and there IS a penalty for trying!

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        • #5
          If you are going to build a designed unit, and Metric threads are called for, and need to buy tap and die, why not buy what the print calls for ?
          Rich
          Green Bay, WI

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          • #6
            I have a fairly complete set of Tekton metric taps and dies I bought for about $40 and they look pretty good, but I haven't used them yet. In general, standard metric threads are pretty close to the nearest equivalent size NF threads, so I would use the fine threads if you don't want to go full metric.
            http://pauleschoen.com/pix/PM08_P76_P54.png
            Paul , P S Technology, Inc. and MrTibbs
            USA Maryland 21030

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            • #7
              3/8NF for me this evening. Why? I only have a 3/8NF tap... Wish I had an NC, now I have to go buy a bolt...

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              • #8
                Originally posted by lugnut View Post
                For the past few days I have been attempting to make the ball turning fixture that I ask Bruno the plans for. Well, after a lot of frustration and nasty words, I have come pretty close to translating the Metric (not the German} into something that I might be able to make work.. Every thing went pretty well until it came time to make the handle that rotates the fixture. Do I use NC or NF threads. My supply of taps and dies is pretty limited. Most are older than most of you guys. Not being but a Hobby Chip Maker, what is the preferred tread for this type of application? I think I need to make a few purchases of taps and dies, but want to get what is best for the job. What say you?
                Without metric taps on hand it might be best to convert to an American thread that's close to the metric, thus staying close to the designers intent. Finding something close just takes a little math. Picking some random numbers to use as an example: Take the basic size of the thread, say it's 10mm, and divide that by 25.4 = .3937 which is a little bigger than 3/8 inch. If the thread pitch is 1.5mm divide that by 25.4 = .059 inch which converts to threads per inch by inverting, as 1 divided by .059 = 16.9, or approximately 17 threads per inch. Looking at these numbers a 3/8-16 thread is pretty close to a 10mm x 1.5mm thread.

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                • #9
                  https://harborfreight.com/metric-dri...set-95529.html

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                  • #10
                    The drawing that Bruno posted for the ball turning fixture is posted in the Shop Made Tools section, post #3962. It is in all metrics. I don't have a problem with converting it to standard US bolt sizes. But being a old farm boy, I have a habit of wanting to lean towards course (NC) threads. I have a lot of NC taps and dies. Should I take the leap and buy some NF taps and dies. I know there must be places where they would be better but not sure where.





                    _____________________________________________

                    I would rather have tools that I never use, than not have a tool I need.
                    Oregon Coast

                    Comment


                    • #11
                      Since all of the bolt specs are just M?, they would correspond to NC threads. If they were metric fine threads, the pitch would be added to the specs.

                      p.s. Wikipedia has a fairly good explanation of where to use coarse and fine threads. The paragraph is right after the chart.
                      Last edited by elf; 10-03-2020, 04:54 AM.

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                      • #12
                        Originally posted by tom_d View Post

                        Without metric taps on hand it might be best to convert to an American thread that's close to the metric, thus staying close to the designers intent.
                        Without metric taps on hand it might be best to just buy a set of metric taps so you can make the device to plans and then you will have metric taps on hand for the next dozen projects that call for them too. They aren't just a one time use item. They also do not need to be expensive, you are doing this as a hobby, not a business.

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                        • #13
                          Look at the application, you know the basic reasons for deciding NF or NC? Use whats best for the task at hand.....otherwise use what you have. Except 10/24. I fired #10 24, dirty, rotten stinking miserable weak assed whiny pain the arse thread. I'm a 10 32 man now
                          in Toronto Ontario - where are you?

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                          • #14
                            You can't really go wrong using fine thread in any metal-to-metal assembly. I do use coarser threads if one of the components is plastic.
                            Southwest Utah

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                            • #15
                              As is often the case, we seem to have conflicting guidance:

                              Originally posted by PStechPaul
                              In general, standard metric threads are pretty close to the nearest equivalent size NF threads, ..... ......

                              Originally posted by elf
                              Since all of the bolt specs are just M?, they would correspond to NC threads. If they were metric fine threads, the pitch would be added to the specs. .....
                              Lynn (Huntsville, AL)

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