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NC or NF Threads ??

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  • #31
    I ended up with quite a lot of 10-32 in some fastener bins I bought, rarely used them . Some nice stainless in there.

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    • #32
      Originally posted by PStechPaul View Post
      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.
      I owned that same set for a while. I have but one thing to say:

      Good f%$#&* luck tapping anything harder than styrofoam

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      • #33
        Ages ago I bought a "big set" of taps and dies from Harbor Freight that had Metric & Imperial taps to 1/2 inch / 12mm. I still have that set. I've broken a few over the years. Mostly from ham handedness. I've used a few until they were dull, but over all it wasn't to bad a set. Every piece in it was good for atleast a few holes/rods. A few years ago I bought a similar set from HF in just Imperial sizes to throw in my service truck and it was total garbage. Several taps were off diameter, and some were just plane dull right out of the box. Some dulled on first use. I still have the original set, and I periodically buy replacement taps to go in and fill empty slots with better taps. I figure the ones that are missing are the ones I use more often, so I replace them with better quality taps.

        *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

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        • #34
          Here is the link to that post:

          https://bbs.homeshopmachinist.net/fo...04#post1901604

          It looks like it is just a plain, old handle. Nothing magic or precise. The handle is at the LEFT side of the drawing and is only partially shown. There are no dimensions or thread specification on the handle. Perhaps our OP has more detailed drawings.

          I see nothing wrong with anything between 3/8-16 and 1/2-13 course threads or 3/8-24 and 1/2-20 fine threads. Any thread in that range should work just fine.

          A tip:

          I sometimes visit the local pawn shops. Some of them have bins of used tools, usually with a good patina of rust. I have purchased taps from them at prices around one dollar each. After a trip through the rust removal bath, usually administered in my ultra-sonic cleaner, most of them are usable. One notable purchase gave me three name brand taps in the 3/8-16 size: taper, plug, and bottom taps. All three cleaned up to a usable state, at least in aluminum. Probably OK for mild steel too, but I haven't tried that. I am working on methods to re-sharpen these old taps and will publish that work when it is done.



          Originally posted by lugnut View Post
          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.




          Paul A.
          SE Texas

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

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          • #35
            I understand about the 10-24 threads, but I avoid using fine threads in aluminum or plastic or anything softer.

            Sarge41

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            • #36
              Originally posted by Bented View Post
              The handle is the most important feature of any piece of equipment, it is the HMI (Human Machine Interface).
              Inappropriate choice of threads can lead to catastrophic failure.

              For instance if the throttle handle mounts for your aircraft call for M10-1.5 threads and you use 3/8"-16 instead the plane will surely crash in use.

              Also incorrect handle thread choice can often cause your balls to have less then optimal sphericity.
              Hi,

              We ain't flyin' no aircraft here. It's a homeshop ball cutter. Rocket surgery isn't required..........
              If you think you understand what is going on, you haven't been paying attention.

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              • #37
                Ain't no use splainin a joke to someone that ain't got no sense of humor.

                Or as we say here in New Jersey, WTF
                Last edited by Bented; 10-03-2020, 09:20 PM.

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                • #38
                  Originally posted by Bented View Post
                  The handle is the most important feature of any piece of equipment, it is the HMI (Human Machine Interface).
                  Inappropriate choice of threads can lead to catastrophic failure.

                  For instance if the throttle handle mounts for your aircraft call for M10-1.5 threads and you use 3/8"-16 instead the plane will surely crash in use.

                  Also incorrect handle thread choice can often cause your balls to have less then optimal sphericity.
                  The FAA would be knocking on your door doing an illegal modification without a supplemental type certificate. On our 747's, mechanics can't even use double sided foam tape to mount a spice rack in the galley, FAA didn't like it.

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                  • #39
                    Originally posted by lugnut View Post
                    .................................................. ............ Do I use NC or NF threads. My supply of taps and dies is pretty limited. .... what is the preferred tread for this type of application?...................................... ........?
                    Lugnut
                    So what you want is an outline of thread use !
                    Having worked in steel Die shops for most of my career . Here are a few that apply to fasteners ( Not to adjustment threads ! )

                    For discussion here, lets call them the "Screw" and the "Hole"
                    So much depends on material - you have 3 variables,
                    (A) Screw and Hole have same "Strength" ( Tensile Strength or TS)
                    (B) Screw material is stronger than Hole material
                    (C) Hole Material is stronger than Screw Material
                    As a rule :
                    1. Screws are stronger when using Fine Thread because the cross-sectional area of the screw is larger than on a Course Thread for same size Diameter
                    2. Threaded depth of Hole is a function of Material Strength - When (A) same material occurs , Max strength is reached at ONE Diameter whether Fine or Course. So a 3/8" thread only needs a 3/8" depth of thread to meet maximum joint strength. If (B) is the case, then longer thread depth is required. You see this with some holes calling out 1-1/2 times diameter or even 2 x Dia,
                    3. The most common case is (B) where the hole is soft , so you want to use a Course Thread as that makes the Hole stronger and the Screw's TS can handle it
                    This is easily seen with an Aluminum Hole(10K TS) and a Steel Screw, or a Mild steel Hole (60K IS) and a Grade 3,5,8, or Cap Screw ( 12.9 M)

                    A few observations using the above
                    If you have the same material for both (A), then tapping deeper than one diameter is a waste of time/effort
                    If (A) tapping Aluminum ( 10,000 TS ) and using a Allen cap screw (175,000 TS) . max strength is reached at 17 X Diameter , but this is impractical as friction becomes a consideration so most such joints use 3x Dia. as a max consideration--even then, the screw is stronger.
                    Use course threads for Aluminum--always !
                    Taps are a function of Cross-sectional Area of the Tap's Root Diameter, thus Tap strength means it is easier to break a Course tap than a fine tap ( Larger Cross-section) . So tapping a hard steel casting with a Fine thread is easier and less breakage occurs.
                    For the record, the absolute worse taps are 10-24 and 1/4-20 . The flute cutting load for the cross-sectional area of the root is ridiculous. Maybe fine for tapping Aluminum or mild iron , but should not be used on harder steels

                    Hope this helps
                    Rich


                    Last edited by Rich Carlstedt; 10-03-2020, 09:53 PM.
                    Green Bay, WI

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                    • #40
                      The only reason I picked on the handle was because I was going to use a 3/8 X 10" NC bolt to make it from. Planed on using the existing treads for the ball handle to attach with and cut the head off and thread the other end to screw into the fixture attached to the main shaft, The only 3/8 die I had was a NC and I thought maybe a NF would add a little more "stout" plus the fact that my 3/8 NC die was dull and refused to cut. I know, I know. t could have spent a hour changing the gears on my lathe but I decided to tough it out with the Die instead. Good old Amazon promised my some new 3/8 dies by Tuesday. A new handle in the plan when the new dies get here.
                      _____________________________________________

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

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                      • #41
                        I found some old threads that delved deeply (or not) into this subject:

                        https://bbs.homeshopmachinist.net/fo...x-32-or-8-x-24

                        https://bbs.homeshopmachinist.net/fo...al-head-screws

                        https://bbs.homeshopmachinist.net/fo...vs-fine-thread

                        https://bbs.homeshopmachinist.net/fo...ivalents-chart

                        https://bbs.homeshopmachinist.net/fo...l-alloy-or-hss

                        I also made a spreadsheet showing that metric coarse (standard) threads are generally finer than imperial coarse threads:

                        Click image for larger version

Name:	Threads_F-C_Met-Imp.JPG
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                        http://pauleschoen.com/pix/PM08_P76_P54.png
                        Paul , P S Technology, Inc. and MrTibbs
                        USA Maryland 21030

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                        • #42
                          Originally posted by lugnut View Post
                          The only reason I picked on the handle was because I was going to use a 3/8 X 10" NC bolt to make it from. Planed on using the existing treads for the ball handle to attach with and cut the head off and thread the other end to screw into the fixture attached to the main shaft, The only 3/8 die I had was a NC and I thought maybe a NF would add a little more "stout" plus the fact that my 3/8 NC die was dull and refused to cut. I know, I know. t could have spent a hour changing the gears on my lathe but I decided to tough it out with the Die instead. Good old Amazon promised my some new 3/8 dies by Tuesday. A new handle in the plan when the new dies get here.
                          GOOD GRIEF! It's a HANDLE! 3/8-16 in place of the M10-1.5 or so will do just fine.

                          Places I prefer to use NF series is where there is either a lot of vibration or if the bolt has to withstand a LOT of tensile pressure. Or if the thread will be used for some manner of adjustment. The longer angle locks in better and is more vibration resistant as a result. And for times I want more tensile strength the fine thread leaves me with a larger cross section of unmolested metal through the threaded area. And for adjustments the finer thread just means a less fussy adjustment.

                          The "GOOD GRIEF" is mostly in jest towards you and perhaps in some criticism of the others suggesing this or that. And especially those that figure you really NEED to rush out and buy a metric tap and die set. As you say, it's a hobby. Sometimes I think there's more than a few around here that forget that a lot of us are doing this for fun and not for income.

                          Please post pictures of the ball turner once it's done. Always nice to see the stuff others have done.
                          Last edited by BCRider; 10-04-2020, 02:32 AM.
                          Chilliwack BC, Canada

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                          • #43
                            I've been ham handed enough to snap handles I might not have if they had been fine thread, but that was 1/4-20 I think and clamping
                            --
                            Tom C
                            ... nice weather eh?

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                            • #44
                              I know it's just a handle, but it really pissed me off when I discovered I didn't the a proper die to do the job right. There is not a place near me where I can just run to and buy materials, so I make do with what I have. I might have maybe 2 dozen metric bolts in my collection and probably 2 hundred pounds of US standard bolts and nuts. The funny thing about building a ball turner is, I already have 3 others that I have made, and I just thought this one is different from others I have seen, and would be fun to make. Besides I need to keep up my feel for my tools and machines.
                              I will post some photos of it in a few days.
                              Thanks guys for you help and input.



                              _____________________________________________

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

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